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Select this Article		Deriving Traffic Flow Patterns from Historical Data Francesc Soriguera Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000456 Posted ahead of print 21 May 2012 Full Text: \| Download PDF
	+ -	Show Abstract The development and decreased cost of technology and communications have brought about a huge increase in the availability of traffic data. With every passing day, traffic management centers must deal with an increased amount of detailed data. Once the real time use of these data is complete, they must be stored for long periods of time. In this long term context, the vast amount of raw data is meaningless, which is a clear example of data asphyxiation. Traffic management centers must aggregate and synthesize the data in order to extract the maximum knowledge from them. Pattern classification is a way to deal with this issue. Traditionally, traffic demand patterns have been easily constructed using ad hoc methods, where the “experience” and “judgment” of the analyst is their main attribute. These procedures lack the required rigor to support current needs in terms of planning and operational management. The present paper proposes a quantitative method to systematically derive traffic demand patterns from historical data. The method is based on the cluster analysis technique, and allows the inclusion of preexistent knowledge, which eases the interpretation and practical use of the results. The proposed pattern classification procedure is applied to five years of hourly traffic volumes on a Spanish highway. The obtained results prove the validity and utility of the method to accurately summarize the seasonal and daily characteristics of traffic demand.

Select this Article		A Methodology for Pavement Design Reliability and Back Analysis Using Markov Chain Monte Carlo Simulation Deepthi Mary Dilip and G. L. Sivakumar Babu Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000455 Posted ahead of print 21 May 2012 Full Text: \| Download PDF
	+ -	Show Abstract Given the increasing cost of designing and building new highway pavements, reliability analysis has become vital to ensure that a given pavement performs as expected in the field. Recognizing the importance of failure analysis to safety, reliability, performance and economy, back analysis has been employed in various engineering applications to evaluate the inherent uncertainties of the design and analysis. The probabilistic back analysis method formulated on Bayes' theorem and solved using the Markov chain Monte Carlo simulation method with a Metropolis‐Hastings algorithm has proved to be highly efficient to address this issue. It is also quite flexible and is applicable to any type of prior information. In this paper, this method has been used to back‐analyze the parameters that influence the pavement life and to consider the uncertainty of the mechanistic‐empirical pavement design model. The load‐induced pavement structural responses (e.g., stresses, strains, and deflections) used to predict the pavement life, are estimated using Response Surface Methodology model developed based on the results of linear elastic analysis. The failure criteria adopted for the analysis was based on the Factor of Safety, and the study was carried out for different sample sizes and jumping distributions to estimate the most robust posterior statistics. From the posterior statistics of the case considered, it was observed that after around 150 msa load repetitions, the mean values of the pavement properties decrease as expected, with a significant decrease in the values of the elastic moduli of the expected layers. An analysis of the posterior statistics indicated that the parameters that contribute significantly to the pavement failure were the moduli of the base and surface layer, which is consistent with the findings from other studies. After the back‐analysis, the base modulus parameters show a significant decrease of 15.8% and the surface layer modulus a decrease of 3.12 % in the mean value. The usefulness of the back analysis methodology is further highlighted by estimating the design parameters for specified values of the Factor of Safety. The analysis revealed that for the pavement section considered, a reliability of 89% and 94% can be achieved by adopting FOS values of 1.5 and 2 respectively. The methodology proposed can, therefore be effectively used to identify the parameters that are critical to pavement failure; and in the design of pavements for specified levels of reliability.

Select this Article		Application of Soft Computing for Prediction of Pavement Condition Index Habib Shahnazari, Mohammad A. Tutunchian, Mehdi Mashayekhi, and Amir A. Amini Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000454 Posted ahead of print 21 May 2012 Full Text: \| Download PDF
	+ -	Show Abstract The Pavement Condition Index (PCI) is a widely used numerical index for the evaluation of the structural integrity and operational condition of pavements. Estimation of the PCI is based on the results of a visual inspection in which the type, severity and quantity of distresses are identified. The purpose of this study is to develop an alternative approach to forecasting the PCI using optimization techniques, including Artificial Neural Networks (ANNs) and Genetic Programming (GP). The proposed soft computing method can reliably estimate the PCI and can be used in a Pavement Management System (PMS) using simple and accessible spreadsheet softwares. A database composed of the PCI results of more than 1250 kilometers of highways in Iran was used to develop the models. The results showed that the ANN‐ and GP‐based projected values are in a good agreement with the field‐measured data. In addition, the ANN‐based model was more precise than the GP‐based model. For more straightforward applications, a computer program was developed based on the results obtained.

Select this Article		Development of a Predictive System for Estimating Fatigue Life of Asphalt Mixtures Using the Indirect Tensile Test Jaeseung Kim and Chulseung Koh Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000452 Posted ahead of print 4 May 2012 Full Text: \| Download PDF
	+ -	Show Abstract Fatigue cracking has been a major problem in asphalt pavement. It would be beneficial for a prediction of fatigue life of asphalt mixtures to be made with minimal effort and time, both at the design and the operating stages of pavement. To be practical, the indirect tension (IDT) test has been widely used for testing both laboratory‐made and field‐cored mixtures; however, a fatigue test using the IDT test needs to be performed in the stress‐controlled mode rather than in the strain‐controlled mode. Results might not be comparative to those from other mixture tests, such as the flexural beam fatigue or uniaxial tension test, so this study employed the viscoelastic continuum damage (VECD) model. The C₁‐S₁ curve, which is a final product of the VECD model, is known as a single‐characteristic curve of an asphalt mixture and is independent of types of loading. Three C₁‐S₁ curves obtained from two fatigue tests and one monotonic strength test using the IDT test were similar when superimposed into a single C₁‐S₁ curve, indicating that the VECD model can be applicable both to the IDT fatigue test and the strength test. This also indicates that the fatigue life of a mixture subjected to sinusoidal strain loading can be determined through the model's damage principles using the IDT test results. Consequently, a system for predicting the fatigue life of asphalt mixtures was developed. It is expected that the predictive system will be useful in estimating the fatigue life of asphalt mixtures fabricated in the laboratory, as well as those cored from field pavements.

Select this Article		Proposals of Using the Simulated Annealing to Optimize Bottleneck Model at Railway Station Kang Liujiang, Jianjun Wu, and Huijun Sun Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000450 Posted ahead of print 28 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract The bottleneck section of railway passenger station is very complex, where many frequently technical and shunting operations are performed with a long time. Moreover, it is also the connection of station tracks, locomotive depot and passenger train stock servicing yard which has great effects on the carrying capacity of railway passenger station. Therefore, there have many optimization problems in engineering project and practice. In this paper, we propose a bottleneck optimization model to enhance the carrying capacity by arranging routes and groups of turnouts reasonably with the consideration of proportionality and minimized total occupation time. The simulated annealing algorithm is provided to solve this programming, and the optimized strategy is given. A case study focused on the bottleneck section optimization in the passenger station of China illustrates the application of proposed model.

Select this Article		Optimizing Longitudinal Alignment in Railway with Regard to Construction and Operating Costs Mostafa Bababeik and M. Saeed Monajjem Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000448 Posted ahead of print 28 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract Designing base line or vertical alignment in railway greatly depends on the designer's experience and if it is not designed accurately, it imposes unreasonable costs during construction and operation period. In this paper, a program is presented to find the best vertical alignment for a track with given horizontal layout. First, the vertical alignment is formulated via mathematical equations, and then an algorithm is developed to produce its geometric configuration. Construction and operating costs which are sensitive to gradient change are expressed as vertical alignment variables and included in the model. Direct search method is employed to solve the objective function, and solution algorithms are encoded by Genetic Algorithm in a program, while some heuristic operators are utilized to cover operational situations. The program, also, provide railway engineers and planners with practical information about the resulting alignment such as time and speed graph, total traction force, and the block capacity. Besides, the model is evaluated by a real example, which verifies algorithms in finding optimal alignment.

Select this Article		Pavement Treatment Short‐Term Effectiveness in IRI Change Using LTPP Data Pan Lu and Denver Tolliver Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000446 Posted ahead of print 28 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract This paper finds that pavement treatment short‐term effectiveness in IRI follows a polynomial relationship with pre‐treatment pavement condition. Pre‐treatment pavement condition is an influential factor of the treatment effectiveness in the short‐term. This paper finds that (1) hot mill overlay can offer average reductions in IRI of 1.44 m/km IRI; (2) crack sealing can offer average reductions in IRI of 0.27 m/km IRI; (3) aggregate seal can offer average reductions in IRI of 0.31 m/km; (4) chip seal can offer average reductions of 0.72.

Select this Article		Using Truck Probe GPS Data to Identify and Rank Roadway Bottlenecks Wenjuan Zhao, Edward McCormack, Daniel J. Dailey, and Eric Scharnhorst Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000444 Posted ahead of print 28 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract This paper describes the development of a systematic methodology for identifying and ranking bottlenecks using probe data collected by commercial Global Positioning System fleet management devices mounted on trucks. These data are processed in a geographic information system and assigned to a roadway network to provide performance measures for individual segments. This work hypothesized that truck speed distributions on these segments can be represented by either a unimodal or bimodal probability density function and proposed a new reliability measure for evaluating roadway performance. Travel performance was classified into three categories: unreliable, reliably fast, and reliably slow. A mixture of two Gaussian distributions was identified as the best fit for the overall distribution of truck speed data. Roadway bottlenecks were ranked on the basis of both the reliability and congestion measurements. The method was used to evaluate the performance of Washington state roadway segments and proved efficient at identifying and ranking truck bottlenecks.

Select this Article		Modelling Automobile Driver's Toll‐Lane Choice Behaviour at a Toll Plaza Avinash Dubedi, Partha Chakroborty, Debasis Kundu, and K. Harikishan Reddy Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000440 Posted ahead of print 28 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract A toll‐lane selection process at a toll plaza can be looked at as an outcome of the choice processes of individual drivers. In this paper an attempt is made to develop a random utility based discrete multinomial choice model for the behaviour of automobile drivers while selecting toll‐lanes at a toll plaza. Specifically, a multinomial Logit model is developed and calibrated using disaggregate level choice data from three toll plazas with different geometry and rates of arrival of vehicles. The calibrated Logit models from the different sites when statistically compared show that a generic model, applicable to all the sites, is possible. Such a generic model is also developed. The use of the proposed model can improve the analysis of traffic flow at toll plazas and ultimately lead to more effective designs of these facilities.

Select this Article		Development of a VISSIM Simulation Model for U‐Turns at Unsignalized Intersections Pan Liu, Ph.D., Xu Qu, Hao Yu, Wei Wang, Ph.D., and Bing Cao Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000438 Posted ahead of print 28 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract The simulation of U‐turns is currently of great interest to many transportation professionals due to the widespread use of indirect driveway left‐turn treatments. In this study, a procedure was proposed to help transportation professionals model U‐turn movements at unsignalized intersections with non‐traversable median cross sections in VISSIM. Behavioral features of U‐turning drivers, such as the priority rule, lane selection, and turning speed of U‐turns were determined using data collected from 13 different locations. A procedure based on genetic algorithm was proposed to calibrate and validate the VISSIM simulation model. Simulation results of the calibrated VISSIM model were compared to field measured capacity, as well as the capacity estimated using gap acceptance models developed in our previous studies. The calibrated VISSIM simulation model yields a Mean Absolute Percent Error (MAPE) of 17.6% and 20.7% for 4‐lane and 6‐lane streets, respectively. The results show that VISSIM provides reasonable capacity estimates for U‐turns at unsignalized intersections with raised median cross sections, after crucial parameters are properly defined and calibrated.

Select this Article		Operational Effects of Drivers Misperception of Horizontal Curvature Y. Hassan, M. ASCE and M. Sarhan Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000436 Posted ahead of print 3 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract The effect of combining horizontal and vertical curves on operational conditions has been the subject of research over the last few years. A number of studies have reported that combining horizontal curves with crest and sag vertical curves would influence the curvature appearance of such combinations. According to these studies, drivers could misperceive the curvature of a horizontal curve when combined with a vertical curve, and this might result in negative operational effects. These negative effects would most notably be in the form of an erroneous driver's speed choice. This study presents a driving simulation experiment that was planned and conducted to examine the effect of driver's misperception of horizontal curvature on driver's speed behavior. The simulation data were analyzed statistically and provided support for the hypothesis that driver's misperception of horizontal curvature affects their choice of speed. The effects of several geometric parameters on speed were also examined including curve radius, algebraic difference of vertical grades, rate of vertical curvature, turning direction, superelevation rate, and sight distance.

Select this Article		Network‐Scale Traffic Modeling and Forecasting with Graphical Lasso and Neural Networks Shiliang Sun, Rongqing Huang, and Ya Gao Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000435 Posted ahead of print 2 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract Traffic flow forecasting, especially the short‐term case, is an important topic in intelligent transportation systems (ITS). This paper does a lot of research on network‐scale modeling and forecasting of short‐term traffic flows. Firstly, we propose the concepts of single‐link and multi‐link models of traffic flow forecasting. Secondly, we construct four prediction models by combining the two models with single‐task learning and multi‐task learning. The combination of the multi‐link model and multi‐task learning not only improves the experimental efficiency but also the prediction accuracy. Moreover, a new multi‐link single‐task approach that combines graphical lasso (GL) with neural network (NN) is proposed. GL provides a general methodology for solving problems involving lots of variables. Using L1 regularization, GL builds a sparse graphical model making use of the sparse inverse covariance matrix. In addition, Gaussian process regression (GPR) is a classic regression algorithm in Bayesian machine learning. Although there is wide research on GPR, there are few applications of GPR in traffic flow forecasting. In this paper, we apply GPR to traffic flow forecasting and show its potential. Through sufficient experiments, we compare all of the proposed approaches and make an overall assessment at last.

Select this Article		Differences of Driving Characteristics between Normal and Emergency Situations and Model of Car Following Behavior Zhi Xu, Xiao Kuan Yang, Xiao Hua Zhao, and Ling Jie Li Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000434 Posted ahead of print 2 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract This paper intends to present results of an exploratory study on differences of driving characteristics between normal and emergency situation as well as to build up the car following model under the emergency evacuation situation. The simulation scenario has been given to create a driving environment under the emergency evacuation situations. Questionnaire investigations and the electrocardiogram /heart rate monitor are used to verify the validity of the driving environment from both subjective and objective perspectives. Perception reaction time (PRT) and the critical headway are taken as two indicators to describe driving characteristics. The result shows that PRT is in accord with normal distribution under both normal and emergency situations. The value of PRT under emergency situation is lower than that under the normal situation. The result also shows that critical headway under emergency situation is smaller than that under the normal situation. Back Propagation (BP) neural network is designed in this study. Combination of the Levenberg‐Marquardt BP algorithm and Bayesian regularization is employed to train the network. Gray‐correlation analysis is conducted to determine what factors have a great impact on the acceleration of the following car. Simulation of the BP neural network using data collected from driving simulator reveals that the BP neural network has a high precision in the prediction of the car‐following model.

Select this Article		Appropriate Regression Model Types for Intersections in SafetyAnalyst Young‐Jun Kweon, P.E., Ph.D. and In‐Kyu Lim, Ph.D. Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000432 Posted ahead of print 2 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract Highway agencies in the United States have started implementing SafetyAnalyst, highway safety management software. Some agencies have been developing or considering developing safety performance functions (SPFs) using local data to maximize the benefits of the software. With multiple years of data on hand, several model types are available for developing the SPFs, yet no reliable guide is found in selecting appropriate model types. To this end, this study examined 11 model types including 8 panel and 3 cross‐sectional models to recommend appropriate model types for intersection SPFs of SafetyAnalyst. 2003–2008 data collected from 18,356 intersections in Virginia were used. A cross‐sectional model with summed or averaged crash frequencies was found to severely underestimate a dispersion parameter that plays a critical role in the empirical Bayes method. Panel models with independent correlation and autoregressive order 1 correlation and a pooled cross‐sectional model were found to be appropriate across all 8 subtypes. Agencies unable to construct panel data and develop panel models can apply the pooled cross‐sectional model that does not require matching the same intersections across different years.

Select this Article		Incident‐Induced Diversion Behavior: Existence, Magnitude, and Contributing Factors Weihao Yin, Pamela Murray‐Tuite, and Kris Wernstedt Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000431 Posted ahead of print 2 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract The need to understand the impacts of diverting traffic is emphasized by growing congestion and delays. In this paper, we examine incident‐induced diversion behavior using loop detector data and incident records on a freeway in Virginia. This work diverges from previous studies by (1) addressing both existence of diversion and its magnitude, (2) relying on field data rather than surveys, and (3) statistically relating diversion behavior and magnitude to quantifiable incident characteristics and traffic conditions. We use a dynamic programming based procedure to identify diversions by isolating transient level shifts and associate the diversions with incident and traffic characteristics and VMS displays through a binary logit model. The magnitude of the diversion is statistically related to traffic conditions via a linear regression model. Our models indicate that the probability of triggering a diversion increases when an incident lasts longer, more general purpose lanes are blocked, and speeds are lower. Our findings about the effects of trip purpose/time and information availability are consistent with previous studies. The magnitude of the diversion, measured by diversion rate, is related to instant traffic flow characteristics, general traffic demand considerations, and the incident characteristics.

Select this Article		Critical Assessment of Measuring Concrete Joint Faulting Using 3D Continuous Pavement Profile Data Yichang (James) Tsai, Yiching Wu, Chengbo Ai, and Eric Pitts Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000430 Posted ahead of print 2 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract Faulting has traditionally been collected using manual methods, which are labor intensive, time‐consuming, and hazardous to workers and drivers. Therefore, alternative methods for effectively and safely collecting faulting data are needed. With emerging laser technology originally designed for crack detection, high‐resolution, full lane‐width coverage, 3D continuous pavement profile data can now be acquired. This paper critically assesses the feasibility of utilizing this 3D continuous pavement profile data for measuring faulting with a special focus on accuracy and repeatability. Controlled field tests were conducted to evaluate the accuracy for faulting in different ranges. Field tests were conducted at highway speeds on I‐16 in Georgia to evaluate the repeatability and feasibility of the proposed method. Results show the proposed method can estimate faulting with an average error less than 1 mm compared with those measured using the Georgia fault meter, and it can achieve reasonable repeatability with a standard deviation less than 1 mm in repeated runs at different highway speeds. Two tests have demonstrated it is feasible to collect faulting data using 3D continuous pavement profile data. Recommendations for future research are also discussed.

Select this Article		Link Journey Speed Estimation for Urban Arterial Performance Measurement Using Advance Loop Detector Data under Congested Conditions Yao‐Jan Wu, Guohui Zhang, Ph.D., and Yinhai Wang, Ph.D. Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000429 Posted ahead of print 27 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Travel speed ties directly to travel time and hence is an important measure for quantifying arterial performance. However, accurately estimating link travel speed for urban arterials is difficult due to traffic fluctuations and stop‐and‐go conditions caused by signal control. This research proposes a two‐step empirical approach to effectively estimating the link journey speeds merely using advance loop detector outputs. The first step is to estimate the spot speed based on advance loop measurements using Athol's algorithm. The robust regression technique can be used to calibrate the speed estimation parameter (or g‐factor) in Athol's algorithm. The second step is to use the proposed simplified speed estimation model to estimate the link speed only using the calculated loop spot speed without any knowledge of signal timing plans. Traffic operations in the central business district of the City of Bellevue, WA are simulated in the VISSIM traffic simulation model. The test results show that only 50 cycles worth of data are need to calibrate g‐factor in loop speed estimation and the same data sets can be used to calibrate the proposed link speed model. Using this model, the average mean absolute error over the study links is reduced from 4.24mph to 1.51 mph. With proper calibration, this average error can be further reduced to 0.91mph. The results are encouraging and satisfactory. The results also show that the accuracy of speed estimation may be further increased when more data are applied for calibration.

Select this Article		Technical Paper Full Bayesian Method for the Development of Speed Models: Applications of GPS Probe Data Xin Pei, Sze Chun Wong, M. ASCE, Yuen Chong Li, and Nang Ngai Sze Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000428 Posted ahead of print 20 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Traffic speed is one of the basic variables that indicate the level of service of a road entity. It plays an essential role in transportation planning and management. This study attempts to establish a prediction model for speed distribution, in terms of average travel speed and standard deviation, using probe vehicle data in Hong Kong. Taking advantage of detailed traffic flow data, obtained from the Annual Traffic Census, a comprehensive traffic information database can be established, using the Geographical Information System technique. The effects of traffic flow, road geometry and weather conditions on speed distribution are determined using the Markov chain Monte Carlo (MCMC) simulation approach Full Bayesian method.

Select this Article		Self‐Similar Behavior of Highway Road Traffic and Performance Analysis at Toll Plazas Malla Reddy Perati, K. Raghavendra, H. K. Reddy Koppula, Mallikarjuna Reddy Doodipala, and Rajaiah Dasari Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000427 Posted ahead of print 8 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Till recently Poisson process has been used to model internet and road traffic queues. It has been established now that internet traffic exhibits self‐similarity which is very different from Poison process. Motivated by this, there were efforts to examine if road traffic is also self‐similar. Earlier efforts in this direction indicate that road traffic in fact is self‐similar. To substantiate this, in this paper, we examine by various methods whether real time traffic on a busy National Highway in India is self‐similar or not. The results from this examination prove that the traffic observed on the Highway is self‐similar. In this paper we also present a novel method based on percentiles for computing Hurst Parameter, which is an indicator for intensity of self‐similarity. The paper also validates the percentile method with two other existing methods. Further to this, the traffic at a toll plaza on the Highway has been modelled as queueing system and performance measures, namely, mean queue length and busy period distribution have also been computed. The numerical results clearly demonstrate that the analysis presented in this paper would be useful for improved designs of toll plazas.

Select this Article		Predicting Lane Utilization and Merge Behavior at Signalized Intersections with Auxiliary Lanes: A Buffalo, New York, Study Jay B. Ring and Adel W. Sadek, Ph.D., A. M. ASCE Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000426 Posted ahead of print 8 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract While auxiliary through lanes (ATLs) are often used to increase the capacity at signalized intersections, their utilization by motorists tends to be significantly lower than continuous through lanes (CTL). This study was designed to: (1) determine whether recently‐proposed models for predicting lane drop utilization are applicable to Buffalo; (2) develop new models for predicting ATL utilization and for predicting drivers. merge behavior at ATLs; and (3) assess the ability of microscopic traffic simulation models to reproduce observed merging behavior. To do this, geometric, traffic count and merge data were collected from select sites in Buffalo. The study shows that lane utilization in Buffalo is a function of total through traffic volume, right‐turning volume, and upstream and downstream land use types. The average merge distance, on the other hand, tends to be a function of the ATL total length, the first lane drop warning sign, the speed limit, and the total through traffic volume. The study also identified the challenges of calibrating merge behavior in microscopic traffic simulation models against field observations.

Select this Article		A Traffic Flow Theory‐Based Stochastic Optimization Model for Work Zones on Two Lane Highways ManWo Ng Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000425 Posted ahead of print 8 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Road maintenance is essential to ensure a safe and efficient transportation system. Unfortunately, work zones can give rise to significant delays to road users. In this paper we address two major limitations in the current work zone optimization models. First, we relax the assumption of determinism and model vehicle arrivals as being stochastic. While previous work has shown that this relaxation is important in the quantification of user delay at work zones, to the best of the author's knowledge, no model exists that explicitly accounts for stochasticity in the optimization of work zones. Second, unlike in previous work where idealized traffic flow modeling techniques have been used, the proposed model employs the traffic flow theory‐based cell transmission model, yielding a more accurate and realistic representation of traffic flow dynamics. The focus in this paper is on two lane two way highways. A case study is presented to illustrate the proposed model.

Select this Article		Freeway Recurrent Bottleneck Identification Algorithms Considering Detector Data Quality Issues Peter (Jing) Jin, Ph.D., Steven Parker, Ph.D., Jie Fang, Bin Ran, Ph.D., and C. Michael Walton, Ph.D., P.E. Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000424 Posted ahead of print 8 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Computer algorithms used to identify recurrent freeway bottlenecks have been studied since the deployment of loop detecting systems. Such algorithms automatically analyze the archived loop detector data and identify potential recurrent bottlenecks and their characteristics, such as location, time of day, and activation rate, for further investigation. In a highway congestion mitigation project, such algorithms can save time and resources for the initial screening of bottlenecks over a large freeway network. These algorithms include rule‐based, contour‐map‐based, and simulation‐based methods. However, existing methods require loop detector data with high accuracy and consistency, which is difficult to achieve in prevailing loop detecting systems. This paper proposes a new bottleneck identification algorithm with strong error and noise tolerance. Several simple de‐noising methods to improve the error resistance of existing algorithms are also proposed. Using statistical error analysis methods, the proposed algorithm and the denoising methods have been calibrated and evaluated using field data collected from two distinct freeway corridors (US 12/14 and I‐894) in Wisconsin, USA. Ground truth data for this study comes from the manual inspection of 287,055 traffic video snapshots within a month. In the evaluation tests, the proposed algorithm can produce quality congestion identification results with fewer false alarms than the existing algorithms, especially when identifying severe bottleneck congestion.

Select this Article		Distribution of Delay in Signalized Intersections: Day‐to‐Day Variability in Peak‐Hour Volumes Reza Noroozi and Bruce Hellinga, Professor, P.Eng Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000423 Posted ahead of print 8 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract The HCM and other analytical methods provide a point estimate of average vehicle delay for a specified lane group over a defined time period (e.g. peak hour). The estimated delay is a function of a number of factors including geometry, signal timings, approach volumes, etc. Some of these factors, particularly, peak hour volume, can be considered to be random variable and therefore the distribution of intersection delay is a function of the distribution of these random factors. This paper presents findings of a study that addresses the variability in estimated HCM delay as a function of the variation of peak hour volumes. For protected movements, the distribution of delay is analytically determined as a function of the distribution of the peak hour volume and the HCM delay equation characteristics. A numerical method is proposed to find the distribution of delay for permitted movements for which capacity changes as a result of variability in the opposing volume. The proposed methods are demonstrated through application to a hypothetical intersection. The results indicate that when the degree of saturation for the average peak hour volume is not far from 1, the HCM point estimate of average delay is not sufficient for evaluating the quality of service or designing the intersection signal timing plan. For example, the results from the hypothetical intersection examined in this paper suggest that for a permitted left turn with an average degree of saturation of 0.77 and an average delay of 37.8 sec/veh (level of service=D), there is approximately 20% probability that the lane group operates at a level of service of E or worse (i.e. delay > 55 sec/veh).

Select this Article		A Hazard‐Based Analysis of Highway Project Development Times G. P. Ong, A. M. ASCE, V. Fitzpatrick, S. Labi, A. M. ASCE, and K. C. Sinha, Hon. M. ASCE Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000422 Posted ahead of print 8 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Transport agencies around the world recognize the importance of on‐time on‐budget delivery of highway projects and understand the need for an efficient transport development process. Past studies on highway project duration and cost estimation were focused on construction, and few studies focused on pre‐construction project delivery from an agency's perspective. This paper presents the use of hazard‐based duration models in investigating the potential risk factors that could affect project development time from planning to letting. A database comprising of over 35 years of highway project data from the state of Indiana was used to develop appropriate models. Out of the three model forms (Weibull, Weibull with gamma heterogeneity and log‐logistic) considered in the paper, it was found that the log‐logistic model is the most appropriate for modeling project development time. For each work category (pavement, bridge and roads/interchange projects), risk factors were identified and their influences on project development time (and consequently, on letting time) investigated. The developed hazard‐based duration models were further applied to demonstrate their ability in predicting the expected project development time for delivery and the project related factors that influence this duration, thereby providing the agency with useful interpretation of associated delivery risks.

Select this Article		Integrated Heteroscedasticity Test for Vehicular Traffic Condition Series Jianhua Guo, Wei Huang, and Billy M. Williams Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000420 Posted ahead of print 23 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract Due to the growing awareness of the importance of the traffic condition uncertainty related studies, traffic condition uncertainty modeling is gaining increasing attention from the transportation research community. In this field, traffic condition uncertainty, gauged mainly by the conditional variance of traffic characteristics, has been investigated primarily with two major approaches as GARCH approach and stochastic volatility approach, lacking of, however, thorough and sound test on the applicability of these approaches. In order to complete this modeling gap and hence lay the theoretical basis for traffic uncertainty related studies, an integrated heteroscedasticity test, including an optimal transformation search and four statistical tests, is proposed in this study. Using real world data collected from 36 stations across four regions in both the United Kingdom and the United States and aggregated at 15‐minute interval as a typical representative, the proposed integrated heteroscedasticity test is demonstrated, validating the heteroscedastic nature of the traffic conditional series. In addition, the effects of transformations are illustrated together with an online short term traffic condition forecasting algorithm as an additional validation of this heteroscedastic nature. On firmly establishing the heteroscedastic nature of the traffic conditions, future studies are recommended to further the modeling of traffic condition uncertainties over a spectrum of time intervals and apply the uncertainty models in various applications such as travel time reliability or the proactive traffic control systems.

Select this Article		Comparison of Driver Behavior by Time‐of‐Day and Wet Pavement Conditions Vinayak V. Dixit, Vikash V. Gayah, and Essam Radwan Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000400 Posted ahead of print 21 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract This study uses the two‐fluid model for traffic flow, to examine driver behavior during both wet and dry pavement conditions, and various times of the day. It was found that parameters in the two‐fluid model known to be strongly affected by driver behavior (particularly driver aggressiveness) were statistically different between wet pavement and dry pavement conditions. The results confirmed that drivers tend to behave more conservatively when the pavement was wet as compared to dry. In addition, the parameters of the two‐fluid model were found to be statistically different for the morning peak period from the midday and evening peak periods. The results of which indicated that drivers behave more aggressively during the morning peak. Though these findings have been observed in previous studies, they have not been quantified using traffic data. This study shows that the two‐fluid model apart from being a measure of network performance may be able to unveil more about driver behavior. There is a strong possibility that the parameters of the model may be used by researchers as a surrogate measure of safety and could lead to a measure to evaluate aggressive driving.

Select this Article		Planning of Fixed‐Route Fixed‐Schedule Feeder Service to Bus Stops in Rural India Sudhanshu Sekhar Das, Bhargab Maitra, and Manfred Boltze Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000419 Posted ahead of print 16 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract Rural feeder service between villages and bus stops is largely a missing component in developing countries such as India. Traditionally, planning of rural feeder service has been carried out without due consideration to indirect costs associated with hard factors (say, walking distance and waiting time) and soft factors (say, crowding inside vehicles) of the service. A case study is presented for planning of rural feeder service with due consideration to direct and indirect costs to users and operational viability of the service. Direct and indirect costs to users are expressed in terms of a comprehensive measure called as “Generalized Cost” (GC). GC is developed on the basis of Willingness‐to‐Pay (WTP) of rural commuters with respect to various attributes of rural feeder service. The work demonstrates the influence of catchment characteristics (i.e. number of villages, size of villages, and spatial separation represented by road network connecting villages to bus stop) on feeder service attributes (i.e. type of vehicle, route, headway of service and fare). It is also shown that planning of feeder service could be instrumental in bringing benefits to rural community. The results presented in the paper are case specific but the methodology can be applied for planning of feeder services in other rural regions.

Select this Article		Sun Glare Impacts on Freeway Congestion: A Geometric Model and Empirical Analysis Andrew M. Churchill, Yorghos Tripodis, and David J. Lovell Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000418 Posted ahead of print 16 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract In this paper, we develop a geometric model for predicting locations and times where sun glare has the potential to affect drivers on roadways. Existing or prospective highway alignments can be considered. The method includes appropriate geometric models of the roadway alignment, astronomical computations for the relative position of the sun in the sky, and corrections for atmospheric refraction. We introduce novel graphical tools to indicate the results of the model, which include sets of time and location where sun glare should be expected. We test the hypothesis that sun glare has an effect on congestion by comparing real speed data from locations and times at which the geometric model indicates the presence of sun glare, with those at which it does not. Sun glare is shown to have a statistically significant impact on mean traffic speeds.

Select this Article		Relationship between International Roughness Index and Straightedge Index Peter Múcka Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000417 Posted ahead of print 13 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract The study presents the regression relationships between two commonly used indicators of longitudinal road unevenness, International Roughness Index (IRI) and the straightedge index. The 290 real longitudinal road profiles records with considering asphalt concrete and cement concrete road surfaces were processed. Five differently defined straightedge indexes, i.e. the deviations between straightedge and profiles were considered. The one‐parameter linear approximation without absolute term seems to be an appropriate model for fitting the unevenness indexes relation. The conversion relationships between five differently defined straightedge indexes were derived. The results were calculated as a function of a straightedge length in the range from 3 m to 7.8 m. The two‐parameter power function showed to be the most suitable approximation model of the straightedge indexes dependence on the straightedge length. The analyzed influence of the different slab lengths of cement concrete profiles on the conversion relationships indicated the marginal impact for the typical slab lengths.

Select this Article		Aggregate Surface Areas Quantified through Laser Measurements for South African Asphalt Mixtures Joseph Anochie‐Boateng, Aff. M. ASCE, Ph.D., Julius Komba, and Erol Tutumluer, M. ASCE, Ph.D. Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000416 Posted ahead of print 13 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract For several decades, efforts have been made by engineers and researchers in the road and airfield pavements, and railroads to develop methods/procedures for accurate quantification of aggregate shape and packing properties. The difficult part of the process has been the fact that aggregate particles have irregular and non‐ideal shapes. New research capabilities, including laser‐based technology can effectively address the difficulties associated with aggregate shape measurements to optimize asphalt mix design. This paper introduces the use of a three‐dimensional (3D) laser scanning method to directly measure the surface area of aggregates used in road pavements in South Africa. As an application of the laser‐based measurements, the asphalt film thicknesses of five typical South African mixtures were calculated and compared with the film thicknesses calculated from the traditional Hveem method. Based on the laser scanning method, a new surface area factors were developed for coarse aggregates used in the asphalt mixtures. Overall, the study demonstrated applicability of 3D laser scanning method to characterize coarse aggregates.

Select this Article		Optimal Multi‐Asset Maintenance Budget Allocation in Highway Asset Management T. F. Fwa, M. ASCE and J. Farhan Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000414 Posted ahead of print 13 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract In a highway asset maintenance management system involving more than one highway asset type, identifying an equitable optimal allocation of available budget to individual asset systems is a major challenge. This is because the following outcomes are desirable: (i) the maintenance needs of all assets are adequately addressed; (ii) the objectives of individual asset systems are optimally satisfied in an equitable manner; and (iii) the objectives of the overall highway asset system are achieved optimally. To achieve these desirable outcomes, this paper proposes a two‐stage approach in solving the dual‐level multi‐asset multi‐objective pavement network maintenance optimal budget allocation problem. Stage I of the approach analyzes the individual multi‐objective asset systems independently to establish for each a family of optimal Pareto solutions. Minimization of maintenance cost is selected as a common objective for the individual asset systems. This serves as the link for interaction with the Stage II analysis. Stage II adopts an optimal algorithm to allocate budget to individual assets by performing cross‐asset trade‐off to achieve the optimal budget solution for the given overall system level objectives. By defining a minimum performance threshold level for each asset type, the Stage II optimization analysis aims to achieve an equitable allocation of budget by maintaining equivalent amounts of performance improvements for the individual asset systems above their respective minimum threshold levels. The conceptual framework of the proposed approach is presented in this paper, together with a numerical example to illustrate the detailed working of the procedure.

Select this Article		Reliability‐Based Risk Analysis of Roadway Horizontal Curves Kesi You, Lu Sun, and Wenjun Gu Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000402 Posted ahead of print 7 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract Reliability‐based analysis of road geometric design has been reported in literatures as a trend in transportation safety study. In the reliability analysis of horizontal curve, the performance function is usually formulated as a function of failure mode of vehicle skidding only. This paper takes into account the failure modes of vehicle skidding and rollover in formulating the performance functions of cars and trucks respectively. A comparative study of three different performance functions for calculating probability of vehicle failure modes is conducted. The results qualitatively show that truck is more vulnerable to skid than car, and is more likely to rollover than skidding on dry pavement. Vehicle's skidding is greatly influenced by vehicle suspension and roll motion. Followed by a sensitivity analysis investigating influences of vehicle parameters and superelevation on vehicle skidding and rollover. In order to make the paper to be practically useful, the probability of failure for the minimum radius recommended by AASHTO Green Book at various super‐elevations and design speeds was computed to investigate reliability of those recommended minimum radius.

Select this Article		Thermal Stresses of PCC Pavements Containing Fly Ash and Slag Yoonseok Chung, S. M. ASCE, Ph.D. candidate, Hak‐Chul Shin, Ph.D., P.E., and Tyson Rupnow, Ph.D., P.E. Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000392 Posted ahead of print 1 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract With the current demand for Portland cement concrete (PCC) sustainability, supplementary cementitious materials (SCMs) are often used in concrete mixtures to improve the mixture properties in both fresh and hardened concrete. In this research, sixteen concrete mixtures (one control mixture, three binary mixtures, and twelve ternary mixtures) with various combinations of fly ash, slag, and Portland cement were fabricated. The thermal and mechanical properties of the selected ternary mixtures were measured at various ages, and the critical temperature gradient through the slab thickness was generated using the enhanced integrated climatic model (EICM). Using the measured mechanical properties, nonlinear temperature gradients obtained from EICM, and CTE gradients throughout the slab thickness, Westergaard‐Bradbury solution was used to calculate the critical tensile stress on the PCC pavements. The analysis results show that all the ternary mixtures with the replacement of 30 % slag and 30 % fly ash, and replacement of 50 % slag and 20 % fly ash did not exceed 100 % tensile stress‐to‐strength ratio at all ages.

Select this Article		One Dimensional Rigid Pavement Temperature Prediction Using Laplace Transformation Dong Wang and Jeffery R. Roesler Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000413 Posted ahead of print 14 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract This paper presents an analytical solution for the prediction of the time‐dependent 1‐D temperature profile in an N‐layered rigid pavement system using Laplace transformation. Temperature at any depth in a rigid pavement system can be estimated using the proposed solution with input data such as pavement layer thicknesses, material thermal properties,and the measured air temperature and solar radiation intensities. The associated initial‐boundary value problem is governed by the classic heat conduction equation with the air temperature and solar radiation considered in the surface boundary condition. Interpolatory trigonometric polynomials, based on the method of discrete least squares approximation, are used to fit the measured air temperature and solar radiation intensities during a user‐defined time period. Relationship between the constants of integration for the ith layer and the first layer are deduced which simplifies the solution process. Model validation with the measured data confirms that the proposed solution generates reasonable temperature profile in the concrete slab of a four‐layer rigid pavement system during two different time periods of the year.

Select this Article		A Classification and Regression Tree Approach for Predicting Drivers' Merging Behavior in Short‐Term Work Zone Merging Areas Qiang Meng and Jinxian Weng Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000412 Posted ahead of print 9 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract This study aims to use the classification and regression tree (CART) approach, one of the most powerful data mining techniques, to predict drivers' merging behavior in the work zone merging area. Based on the eight factors affecting drivers' merging behavior, a binary CART is built using the merging traffic data collected from a short‐term work zone site in Singapore. The CART comprises 7 levels and 15 leaf nodes to predict drivers' merging behavior in the work zone merging area. The results show that the CART provides much higher prediction accuracy than the conventional binary logit model. Traffic engineers can easily understand how drivers make merging/non‐merging decisions. This demonstrates that the CART approach is a good alternative to investigate drivers' merging behavior in work zone merging areas.

Select this Article		A Unified Mechanistic Approach for Modeling Tests of Unbound Pavement Materials Kimberly Hill, Bereket Yohannes, and Lev Khazanovich Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000411 Posted ahead of print 9 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract Several tests are used for the characterization of unbound materials for pavement applications. The resilient modulus has been one of the most common tests for design specification of unbound materials. The California Bearing Ratio (CBR) is another laboratory test that is frequently used. The Dynamic Cone Penetrometer Test (DCP) is a more common test for in situ quality assessment / quality control of unbound materials. For better connection between design and QA/QC it would be helpful to have a reliable, mechanistic method for correlating test results. This is particularly true for the use of new materials, for which there is not an extensive body of data to empirically draw such connections. This paper presents a framework for a unified approach for modeling these tests. A Discrete Element Method is used to simulate the California Bearing Ratio (CBR) test, the DCP test, and the resilient modulus test. An initial evaluation demonstrated that the simulations are capable to account for the effect of aggregate shape, size, gradation, friction, and stiffness. As such, this methodology shows promise for the development of mechanistic‐based correlation between test results. These results are presented, along with some limitations of the current model and challenges for the future.

Select this Article		Thickness Design of PCC/FBC Composites for Secondary/County Roads Nader Ghafoori, Dara Nyknahad, and Li Wang Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000410 Posted ahead of print 10 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract Tests were conducted in the laboratory and field to determine the extent to which fluidized bed combustion (FBC) spent bed and pulverized coal combustion (PCC) fly ash, by‐products of the coal industry, can be used in low‐volume county and secondary roads. Various proportions of pre‐hydrated FBC spent bed, as a secondary aggregate and an agent to activate pozzolan oxides; PCC fly ash, as a primary cementitious binder; natural fine aggregate, as a primary filler; and a low dosage of Portland cement, as a secondary cementitious compound, were blended and compacted at their optimum moisture content to ascertain their suitability as base course materials. These tests and experiments were used to assess the performance of the selected PCC/FBC base course composites. Based upon the results, thickness design tables of PCC/FBC base courses were developed. Results indicate that the engineering properties of the PCC/FBC composites exceed those of the conventional mixes used in low‐volume roads. The field results verified that the engineering characteristics of the laboratory mixtures can be easily duplicated in field.

Select this Article		Investigating Benefits of Intellidrive^SM in Freeway Operations — Lane Changing Advisory Case Study Hyungjun Park, Ph.D. and Brian L. Smith, F. ASCE, Ph.D., P.E. Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000407 Posted ahead of print 12 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract IntelliDrive^SM, the integration of vehicles and the infrastructure through wireless communication, has generated great interest in the transportation community. It is widely expected that IntelliDrive^SM will support significantly improved transportation operations. However, there have been few studies investigating (a) how IntelliDrive^SM will be used to improve operations, and (b) how to estimate expected benefits of IntelliDrive^SM operations applications. In this study, the research team investigated the application of IntelliDrive^SM to address merging conflicts created by freeway on‐ramps. While merging conflicts contribute significantly to freeway congestion, transportation engineers have limited options with existing traffic surveillance and management tools. IntelliDrive^SM offers the potential for more active management of the surface transportation system, providing capabilities that may be of significant benefit in ramp management. In this research, a lane changing advisory algorithm was developed to explore the potential of IntelliDrive^SM in improving freeway ramp management. Utilizing new IntelliDrive^SM capabilities (highly detailed individual vehicular data and personalized advisory information provision), the proposed algorithm attempts to reduce merging conflicts by encouraging early mainline freeway lane changes to create more space in ramp merging areas. An evaluation of the algorithm was conducted using a PARAMICS microscopic simulation model of a heavily traveled freeway network in Orange County, California, for morning peak hours. The results have revealed that IntelliDrive^SM has the potential to increase vehicle miles traveled by up to 4.3% and reduce vehicle hours traveled by up to 4.6%, which resulted in up to 9.3% higher average speeds, in the best case. However, the results also indicated that, in order to achieve the greatest possible benefits, the proposed algorithm requires very high compliance of drivers as well as near full deployment of IntelliDrive^SM.

Select this Article		Influence of Warm Mix Additives on Polymer Modified Asphalt Mixture Properties Hakseo Kim, Soon‐Jae Lee, and Serji N. Amirkhanian Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000406 Posted ahead of print 6 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract The objective of the study presented in this paper was to investigate the influence of warm mix additives on polymer modified asphalt (PMA) mixtures in regards to engineering properties. Twelve PMA mixtures (four control PMA mixtures and eight warm PMA mixtures) were prepared using two additives (Aspha‐min® and Sasobit®), two binder sources, and two aggregate sources. Evaluation of all PMA mixtures included the following testing procedures: tensile strength ratio (TSR), Asphalt Pavement Analyzer (APA), resilient modulus, and indirect tensile strength (ITS) after long‐term oven aging. In general, the results from this research indicated that (1) the PMA mixtures containing the additives can satisfy the current Superpave mixture requirements, including moisture susceptibility and rutting resistance, and (2) there was no statistical differences between the control and warm PMA mixtures for the properties evaluated in this study, suggesting that the use of WMA technologies into PMA mixes is expected to have no negative effect on the mixture's engineering properties.

Select this Article		Analysis of Critical Structure Responses for Flexible Pavements in NCHRP 1‐37A Mechanistic‐Empirical Pavement Design Guide Yanqing Zhao, Wanqiu Liu, and Yiqiu Tan Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000405 Posted ahead of print 6 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract Accurate determination of critical structure responses plays a vital role in the ability of the Mechanistic‐Empirical Pavement Design Guide (MEPDG) to achieve a reliable pavement design. In the MEPDG the responses generated by a single axle are evaluated at a series of pre‐defined locations, and responses under multiple axle gears are determined using the responses from a single axle following the principle of superposition. This research indicates that the approach currently employed in the MEPDG is able to identify the critical location and obtain the critical response for a tandem axle, while it is inadequate for a tridem or quad axle. The primary reason for the inadequacy is that the response along the outside axle of a tridem or quad gear is not computed and compared to responses at other locations. The erroneous critical location identified by the MEPDG for a tridem or quad axle will lead to an underestimated critical response and consequently an over‐predicted pavement life. The results show that the fatigue lives of asphalt concrete (AC) and cement stabilized mixture (CSM) layers could be over predicted by up to 50% and 200%, respectively. A new set of analysis locations are recommend in this study and equations for computing responses under multiple axle gears using the principle of superposition are proposed for accurate determination of critical responses and prediction of pavement performance.

Select this Article		Traffic Signal Optimization with Greedy Randomized Tabu Search Algorithm Ta‐Yin Hu and Li‐Wen Chen Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000404 Posted ahead of print 6 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract Although advanced technologies, such as detection techniques and controllers, have been incorporated within Advanced Traffic Management Systems (ATMS), pre‐timed signal control still plays an important role in traffic control and management. A wide variety of techniques have been proposed to generate optimal or near‐optimal solutions for signal optimization problems. However, only a limited research has been devoted to the application of tabu search in the signal optimization problem. The characteristics of tabu search could provide accuracy and efficiency with careful design of local search methods. This research applies a randomized meta‐heuristic algorithm, greedy randomized tabu search (GRTS), for network‐level signal optimization problems. With the flexibility of the GRTS, detailed representations of signal control settings could be added easily. In order to compare the performance of GRTS with other algorithms, Genetic algorithm (GA) is chosen and implemented. The performance of the GRTS is investigated in numerical analysis in two networks, including a test network and a real city network. Numerical experiments on the test network are used in the comparison of the GA and GRTS algorithms. Numerical experiments on the real city network are conducted to illustrate possible benefits from the proposed approach. The results show that more than 25% reduction of travel time can be achieved for medium and high demand levels.

Select this Article		Time Series Analysis and Models of Freeway Performance Paul J. Ossenbruggen and Eric M. Laflamme Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000403 Posted ahead of print 6 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract This paper describes a study whose primary purpose is to better understand the relationship between freeway traffic flow and speed. Incidents of recurrent and non‐recurrent congestion were encountered at six radar collection northbound locations on New Hampshire interstate I‐93 in July 2010. The root cause for the onset of the recurrent congestion is explained with exploratory data analyses and a time series modeling approach. A complex combination of present and past values of traffic flow, speed and congestion state, a “congestion history of lingering effect” variables, can explain the triggering and mitigation of congestion events for a highly volatile traffic environment. The approach includes two mathematical models: (1) a generalized additive binomial model to forecast the probability of congestion, and (2) state space models of speed and flow. The state‐space models use a dynamic linear model (DLM) with switching structures to describe the bimodal distribution of speed and flow in the free‐flow and congested states. Model selection, parameter estimation and checking are presented.

Select this Article		Evaluation of Superpave HMA mixture properties at the plant versus behind the paver: Statistical Comparison of QC and QA data. Sahand S. Karimi, Dimitrios G. Goulias, and Charles W. Schwartz Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000399 Posted ahead of print 23 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract State highway agencies concerned with lower asphalt levels and potential durability problems in hot mix asphalt (HMA) mixtures designed with Superpave have lead efforts to explore strategies for improving Superpave mix design. This study addressed the differences in HMA properties that have been observed over the years between samples taken at the plant versus behind the paver for Superpave designed mixtures in Maryland. A large set of Maryland State Highway Administration (MSHA) quality assurance (QA) and quality control (QC) data were analyzed statistically in the context of current specifications. Statistical analysis found that the means and standard deviations of the QC and QA data represent different populations. Since the material leaving the asphalt plant is the same material that is then compacted behind the paver, some relationship between the plant and field properties is expected. However, attempts to define transfer functions between QA and QC measurements in order to use both data sets in HMA acceptance testing encountered low levels of statistical significance.

Select this Article		Application of GLASSO in Variable Selection and Crash Prediction at Unsignalized Intersections Kirolos Haleem and Mohamed Abdel‐Aty Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000398 Posted ahead of print 23 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract In this paper, we propose a new promising variable screening technique to select important covariates, as well as to improve crash prediction; the group least absolute shrinkage and selection operator (GLASSO). GLASSO's main power lies in its ability to deal with datasets having large number of categorical variables, the case in this study. Identifying the significant factors affecting safety of unsignalized intersections was also an essential objective. Two applications of GLASSO were investigated; before fitting the negative binomial (NB) model, and before fitting the promising multivariate adaptive regression splines (MARS) technique using extensive data representing 2475 unsignalized intersections. Regarding the NB models, GLASSO yielded close prediction capability to the backward deletion and random forest techniques. Also, MARS model fitting after using GLASSO relatively outperformed that after using random forest, with similar prediction performance. Due to its outstanding performance with categorical variables and its simplicity, GLASSO is recommended as a promising variable selection technique. Some significant predictors affecting unsignalized intersections' safety were traffic volume on the major road, upstream and downstream distances to the nearest signalized intersection, and median type on major and minor approaches.

Select this Article		An Evaluation Procedure for Mutually Exclusive Highway Safety Alternatives under Different Policy Objectives Snehamay Khasnabis, MASCE, Sabyasachee Mishra, and Chirag Safi Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000397 Posted ahead of print 23 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract The purpose of evaluating mutually exclusive alternatives is to select the one with the highest benefits for implementation. A number of analytic techniques are available for such evaluation purposes. Four such techniques: Cost Effectiveness (C/E), Benefit Cost Ratio (B/C), Internal Rate of Return (IRR), and Pay‐off Period (PP) are discussed in this paper, including their theoretical foundation and data requirements, Also discussed are the measures of effectiveness (MOE) associated with each of these techniques, and how these are to be interpreted. Alternatives to be selected for implementation following such evaluation can typically be funded under different policy objectives. Three such objectives are identified in the paper: Objective A, constrained resource perspective; Objective B, investment perspective; and Objective C, face value perspective. The possible relationship between the alternative selection and program is discussed in the paper. A case study for a set of six mutually exclusive highway safety alternatives is presented using the four analytic techniques and three objectives, resulting in various possible solutions. Results show that under compatible assumptions, and for a given policy objective, the outcome of the evaluation is not affected by the choice of the analytic technique. However, for a given analytic technique, the outcome may be affected by the choice of the policy objective chosen. The principles presented are relevant for most public projects (e.g. transit, airports, etc.) involving the investment of taxpayer resources, even though the case study involves a highway safety project.

Select this Article		Traffic Performance in Signalized Intersection with Shared Lane and Left‐Turn Waiting Area Established Yaping Zhou and Hongbin Zhuang Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000396 Posted ahead of print 23 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract This paper highlights the left‐turn waiting area in intersection and proposes a different perspective for measuring capacity of the traffic flows which permitting the through vehicles to queue on the left‐lane in protected signal operation. The impact of flow diverting from through lanes on left‐lane is quantitatively analyzed with random service system theory and probability theory. The utilization of left‐turn waiting area significantly improves the discharge rate of through‐lane without compromising the efficiency of left‐turning flows, thus reducing the average vehicle delay. A typical intersection with different capacity of left‐turn waiting area is presented to verify the advantage of shared‐use operation in the average delay. Besides, effects of the length of left‐turn waiting area, green ratio and left‐turn proportion on the capacity in shared‐lane are constructed in different conditions. The relationships between these parameters and the actual capacity are presented to show the trade‐off between shared‐use and the exclusive configuration. Theoretical analysis and simulation results show that the shared‐use style still works even the arrival rate of through flows reach the road capacity which may result in congestions.

Select this Article		Effects of fillers on properties of asphalt concrete mixture Anggraini Zulkati, Wong Yiik Diew, and Sun Darren Delai Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000395 Posted ahead of print 23 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract The role of filler on the mechanical performance of asphalt concrete mixture was investigated. Three wearing course (W3B) mixtures incorporating granite, hydrated lime and kaolin as filler fraction were evaluated by the Marshall mix design method to determine their optimum asphalt content. Using hydrated lime or kaolin as a filler requires more asphalt due to their relatively higher specific surface area. The highest stiffness performance was found for W3B‐hydrated lime, followed by W3B‐granite and W3B‐kaolin mixtures. W3B‐hydrated lime and W3B‐kaolin mixtures exhibited higher deformation resistance than that of W3B‐granite mixture. It was found that the presence of filler in an asphalt concrete mixture affects the mixture's performance in three ways: filler influences the amount of asphalt content, filler affects the workability during mixing and compaction, and the resultant properties of asphalt‐filler mastic contribute to the mixture's performance. It is emphasized that the property of filler determines its interaction with asphalt and its contribution to the mixture's performance.

Select this Article		Modeling Origin‐Destination Effects on Roundabout Operations and Inflow Control Vinayak V. Dixit Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000394 Posted ahead of print 23 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Traffic flows around roundabouts have been found to be dependent on origin‐destination flows, but the true nature of this relationship has not been properly understood. Present analyses are based on either gap acceptance models or empirical models. These models do not properly account for the impact of origin‐destination flows on roundabout operations. This has limited the possibility to develop strategies that improve roundabout operations, by controlling inflows. This research proposes a theory to analyze roundabout traffic flows and a strategy to determine inflows into a roundabout that would maximize the outflow from the roundabout. This strategy could be implemented through use of signals to meter vehicles at the entry. To achieve this, a theoretical framework was proposed based on the Macroscopic Fundamental Diagram for urban networks. The theory and strategy is then tested using microscopic simulation. It was found that the outflow from a roundabout is dependent on the average flow, and the average trip length around the roundabout. The average trip length is a function of the OD flows.

Select this Article		New Approach for Developing an Asphalt Concrete Overlay Transition Standard Thomas Darby, P.E, Mohamed Elfino, Affan Habib, Ph.D., P.E.,, Harikrishnan Nair, P.E., A.M.ASCE, and Sean Nelson Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000393 Posted ahead of print 21 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Smooth transitions are necessary to ensure the desired ride for the traveling public. Transitions are used within projects as the new pavement approaches a bridge to avoid adding unnecessary dead load on the bridge. Also as roadways pass beneath bridges, transitions are used to avoid encroaching on the existing vertical clearance. This paper describes Virginia Department of Transportation (VDOT) efforts to develop an effective standard for transition details. An in‐depth analytical model considering the vehicle dynamics was developed to establish the transition lengths for various overlay thicknesses and speed limits. Virtual profiles using these lengths and overlay thicknesses were generated to assess the ride over the transition. Simplified methods to calculate transition lengths were introduced.

Select this Article		Life‐Cycle Cost Analyses for Road Barriers H. Karim, R. Magnusson, and K. Natanaelsson Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000391 Posted ahead of print 17 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract This study aimed at developing a new approach for analyzing life‐cycle costs for road barriers during the road planning and design process. A method called “Activity‐Based Life‐Cycle Costing using the Monte Carlo Simulation” was used to analyse and calculate the life‐cycle costs. The results show a potential for increasing efficiency throughout the road planning and design process by minimizing the life‐cycle costs of road components. The results also show that implementation of life‐cycle cost analyses in the road planning and design process is possible, but difficult, mainly due to lack of relevant data.

Select this Article		Pavement Design Optimization Considering Costs and Preventive Interventions João Santos and Adelino Ferreira Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000390 Posted ahead of print 17 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract In Portugal, as in many other countries, due to the economic crisis, the trend of budgetary pressures on highway agencies is increasing. At the same time, road users are increasingly demanding in terms of highway quality, comfort and safety. Several highway projects have been delayed because of budget constraints. To meet these challenges highway agencies are looking for more cost‐effective methodologies for pavement management at project‐level. This paper presents a new pavement design optimization model, called OPTIPAV, which considers pavement performance, construction costs, maintenance and rehabilitation costs, user costs, the residual value of the pavement at the end of the project analysis period, and preventive maintenance and rehabilitation interventions. It was developed and programmed to help pavement designers to choose the best pavement structure for a road or highway. The results obtained by the application of the new pavement design optimization model clearly indicate that it is a valuable addition to the road engineer's toolbox.

Select this Article		Application of Paths Information in Network Design Problem Pedram Izadpanah and Hedayat Z. Aashtiani Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000389 Posted ahead of print 17 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract In a discrete network design problem, an optimal subset is chosen from a set of proposed link additions to an existing road network in order to minimize the total cost of users. The problem has been pointed out as a complex problem in the transportation planning literature. The main source of complexity is that the problem is a bi‐level program in which the lower level program is a traffic assignment problem. In this paper, a path‐based traffic assignment problem is used as the lower level problem. The path‐based algorithms not only provide the link‐flow solution, but also the useful path‐flow solution (path information) that may be required or used in certain applications, such as network design problem. To solve a network design problem, the traffic assignment problem will need to be solved many times. The main objective of this paper is to expedite the solution of the network design problem by initializing traffic assignment problems with path sets already found in previously performed traffic assignments. The rationale behind this idea is that the addition of a number of proposed links to a network will not change the used paths for the majority of origin‐destination (OD) pairs. In this paper, the network design problem is solved by a branch and bound algorithm for a small network and a relatively large network. It is shown that the proposed method is capable of reducing the computation time to one‐fifth in real size networks.

Select this Article		Financial Consequences of Delaying Pavement Rehabilitation — A Case Study Using LTPP Data Ying Xu and Yi‐Chang Tsai Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000387 Posted ahead of print 14 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Transportation agencies have suffered stringent funding shortages for the past several years. As a result, many pavement preservation and rehabilitation projects have been substantially delayed. The financial consequences of delaying pavement rehabilitation need to be quantified so funding needs can be justified scientifically. Although studies based on hypothetical data have been conducted to evaluate the impact of delaying treatments, there is no research using actual data to quantify the financial consequences of delaying pavement rehabilitation. This study is motivated by the need to remedy this situation. A method that quantifies the financial consequences of delaying rehabilitation using real world data is proposed. The proposed method uses life‐cycle cost analysis (LCCA) and a composite performance indicator, pavement condition rating (PCR), to determine the treatment timing. The proposed method is validated using actual pavement performance data and maintenance history from the Long‐Term Pavement Performance (LTPP) Specific Pavement Studies (SPS‐5) in California. These pavement sections have the same pavement structure, traffic volume, environmental features, and similar rehabilitation treatments, but they have different treatment timings. Their annual life‐cycle costs are computed and compared to quantitatively evaluate the financial consequences of delaying treatment. Preliminary results show that delaying rehabilitation of pavement sections (pre‐rehabilitation PCR value <60) increases the equivalent uniform annualized cost (EUAC) by approximately 27.7% for a 2‐inch overlay and 28.3% for a 5‐inch overlay compared to the timely rehabilitation of pavement sections. Future research is also discussed in this paper.

Select this Article		Options for Hauling Fully‐Loaded ISO Containers in the United States Garreth Rempel, Ph.D., P.Eng., Maryam Moshiri, EIT, S. M. ASCE, Craig Milligan, EIT, S. M. ASCE, Jason Bittner, M.P.A., and Jeannette Montufar, Ph.D., P.Eng. Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000386 Posted ahead of print 14 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Civil engineers plan, design, manage and guide investments in surface transportation. Truck weight limits are inextricably linked to the consideration of pavements, bridges, safety, asset management, sustainability, jobs, and economic productivity. The U.S. 36.3 t cap for gross vehicle weight (GVW), and the Federal Bridge Formula B (FBF B) constrain truck movement of 32.5 t full ISO (International Organization for Standardization) containers. This study identifies the options — and associated implications — for trucks to transport full containers notwithstanding FBF B and the cap. We conducted a national investigation of truck weight regulations across 50 states to identify options, with 28 cases involving telephone interviews. Results show the options are complex, vary by state, result in a patchwork of routes, and include: (1) non‐divisible permits; (2) special haul routes; (3) grandfather rights; (4) state roads; (5) tare reduction; and, (6) operation outside formal regulations. Containerships, railroads, ports, and highways of U.S. trading partners each accommodate full containers. Conditions identified in this paper can result in underutilization of the productivity and efficiency benefits afforded by international standardization.

Select this Article		Evaluation of Operational Effects of Joint Managed Lane Policies Chih‐Lin Chung and Will W. Recker Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000385 Posted ahead of print 14 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract This paper presents a method to evaluate the operational effects of managed lane policies—vehicle eligibility, access control, pricing, and the number of managed lanes—that form a policy combination set. Two macroscopic methods are developed to pre‐screen the set via simple criteria, followed by integer linear programming with multiple objectives and constraints to identify the non‐inferior policies among the downsized set. The approach is demonstrated on the southern California SR‐57 corridor. The application eliminates twelve of possible twenty policy combinations by the macroscopic methods, and generates four non‐inferior policies—the existing high‐occupancy vehicle lane operation and three additional potential high‐occupancy toll lane policies—in terms of maximum vehicle and passenger throughput, and minimum vehicle hour traveled and travel time variance. The pre‐screening efficiency of the macroscopic stage, ranging from 0 to 95%, is affected by the initial policies and traffic conditions. It is concluded that the approach can substantially assess a larger policy set and effectively identify the operational effects of joint manage lane policies.

Select this Article		Hierarchical Markov Chain Monte Carlo Simulation for Modeling Transverse Cracks in Highway Pavements Leslie N. O. Mills, A. M. ASCE, Nii O. Attoh‐Okine, P.E., M. ASCE, and Sue McNeil, P.E., M. ASCE Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000383 Posted ahead of print 12 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Transverse cracks are distresses whose initiation and propagation affect the stability and structural integrity of the highway pavement. They are caused by load, moisture, temperature, construction defects or a combination of the above. Cracking leads to inherent pavement defects that are exacerbated by moisture infiltration as well as the formation of other pavement distresses like roughness with their attendant problems to roadway agencies and users. One feature of transverse cracks is the spontaneity of their initiation and the uncertainty of their propagation. As a result, modeling the formation and spread of transverse cracks requires a framework within which uncertainty can be expressed explicitly. This research seeks to use a statistical approach to model the propagation of transverse cracks on road pavements in Delaware. The aim is to investigate how hierarchical Markov Chain Monte Carlo (MCMC) simulation performs in estimating and predicting the spread of transverse cracks without neglecting their associated uncertainty. Hierarchical MCMC models use the Bayesian approach which accounts for uncertainty in pavement distresses.

Select this Article		A Novel Stochastic Procedure for Designing Yellow Intervals at Signalized Intersections Ahmed Amer, Hesham Rakha, and Ihab El‐Shawarby Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000381 Posted ahead of print 7 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Driver behavior while approaching high‐speed signalized intersections at the onset of a yellow indication varies as a function of many parameters including: age, gender, perception‐reaction time, and acceptable deceleration levels. This paper develops a novice approach for computing the clearance interval duration that explicitly accounts for the reliability of the design (probability that drivers do not encounter a dilemma zone). Lookup tables are developed to assist practitioners in the design of yellow timings. The approach is demonstrated using data gathered along the Smart Road test facility for dry and clear weather conditions for two approach speeds: 72.4 km/h and 88.5 km/h. Each data set includes a complete tracking of the vehicle every deci‐second within 150 m before and after the intersection. A total of 2016 signal stopping records were gathered. Using these data, models that characterize driver perception‐reaction times and deceleration levels are developed. Based on these models, lookup table are developed to assist practitioners in the design of yellow timings, that reflects the stochastic nature of driver PRT and deceleration levels.

Select this Article		Cross‐Entropy as an Optimization Method for Bridge Condition Transition Probability Determination Tara Reale and Alan O'Connor Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000379 Posted ahead of print 7 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Much research has been carried out in recent years as to the most appropriate manner in which to obtain suitable transition probabilities for use in Markovian‐based infrastructural deterioration models. Although many optimisation algorithms have been applied in the process, a review of the literature has shown that the methods in practice may benefit from the use of more sophisticated search algorithms. Consequently this paper focuses on the applicability of Cross‐Entropy, an iterative method pioneered by Reuven Rubinstein in 1997, as a robust, efficient solver for use in the derivation of these probabilities. An advantage of this method is that through the use of a smoothing parameter, it tends to avoid becoming stuck in the bound constraints of the problem. This value is usually taken to be arbitrarily between 0.6 and 0.9, but was included here as another variable to be optimized, thereby adding to the accuracy of the method. Two different objective functions were compared and the use of stationary versus non‐stationary Markov chains was also investigated.

Select this Article		Evaluation of Effectiveness and Cost‐Effectiveness of Asphalt Pavement Rehabilitations Utilizing LTPP Data Qiao Dong, Ph.D. and Baoshan Huang, Ph.D., P.E. Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000378 Posted ahead of print 7 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract This paper analyzed the effectiveness and cost‐effectiveness of several asphalt pavement rehabilitations by investigating the LTPP database. The multiple regression method was employed to evaluate the influence of overlay thickness, pavement thickness, traffic volume and pre‐overlay pavement conditions on the effectiveness and cost‐effectiveness. International Roughness Index (IRI) was selected as an indicator of pavement performance. The post‐rehabilitation IRI, IRI‐drop, roughness increase after rehabilitation and the “benefit” were used as the measures of treatment effectiveness. The results of the presented analyses indicated that thicker overlay and milling reduced the roughness after rehabilitation. Thin overlay, high traffic level and poor pre‐rehabilitation pavement condition increased the deterioration rate of new overlay. Using reclaimed asphalt material did not influence the treatment performance but was cost‐effective in reducing the roughness of new overlay. For a certain deterioration rate, there was an optimized pre‐rehabilitation roughness value or time for applying maintenance treatment.

Select this Article		Short‐ and Long‐Term Evaluation of Asphalt Concrete Strain Gauge Installation Methods Applied to the KHCTR Youngguk Seo, Ph.D. and Jae‐Hoon Lee Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000377 Posted ahead of print 7 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract In the present study, three strain gauge installation methods (mound, trench‐cut, and block‐out) are evaluated to propose a set of methods that are appropriate for different layers of Hot Mix Asphalt (HMA) pavements. The block‐out method is also improved to minimize strain gauge mislocations (i.e., installation offsets). Field tests show that the improved block‐out is suitable for most layers, except for a thin surface in which the mound should be used. To validate the proposed methods, 374 strain gauges are installed at different layers of thirty‐three HMA pavement sections (48 in surface, 157 in intermediate and 169 in base) at the Korea Highway Corporation Test Road (KHCTR) and their initial and long‐term performances are monitored at different times. In addition, the failure rates of embedded strain gauges are correlated with the evolution of the overall pavement conditions and key distresses at selected sections from 2003 to 2007.

Select this Article		Determination of Damage Development in Asphalt Concrete Using Small Scale Accelerated Pavement Testing via Frequency Domain Analysis Approach Sudip Bhattacharjee, A. M. ASCE and Rajib B. Mallick, M. ASCE Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000376 Posted ahead of print 24 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract To predict the pavement response correctly at any condition, the constitutive relation between stress and strain will require the use of a damaged modulus. Several asphalt concrete slabs constructed in the laboratory using vibratory roller compactor and instrumented with strain gauges and thermocouples were tested under the one‐third scaled accelerated loading device called MMLS3. A frequency domain approach has been used to analyze the continuous strain data. The constitutive equation in time domain has been transformed to frequency domain using the Fourier transform technique and the complex modulus values have been determined continuously during the loading. The results indicated that complex modulus is affected by the combined effect of loading and temperature. A general trend of reduction of complex modulus due to these factors has been observed in the study. The analysis results indicate that the frequency domain approach is an efficient and better way to handle large amount of data generated in long term pavement studies and it can be used to determine the change in the complex modulus due to loading.

Select this Article		Quantifying Loop Detector Sensitivity and Correcting Detection Problems on Freeways Ho Lee, Ph.D. Candidate and Benjamin Coifman, Ph.D. Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000375 Posted ahead of print 17 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract Loop detectors are the most commonly used vehicle detector for freeway management. A loop detector consists of a physical loop of wire embedded in the pavement connected to a sensor located in a nearby cabinet. The sensor detects the presence or absence of vehicles over the loop and typically allows a user to manually select the sensitivity level of operation to accommodate for a wide range of responsiveness from the physical loop. In conventional practice, however, it is difficult to know the physical loop's responsiveness, which makes selecting the appropriate sensitivity level difficult. If the sensitivity and responsiveness are poorly matched it will degrade the detector's data and the performance of applications that use the data, including: traffic management, control, and traveler information. To resolve this often overlooked problem, this paper presents an algorithm to assess how well a loop detector's sensitivity is set by calculating the daily median on‐time from the data reported by the loop detector. The algorithm can be incorporated into conventional controller software or run off‐line. The result can be used both to correct the detector on‐times for an inappropriate sensitivity setting in software (e.g., via a multiplicative correction factor) and to trigger an alarm to dispatch a technician to adjust the hardware sensitivity. Plotting the daily median on‐time over months or years can show how the detector performance evolves. The approach is then transposed to dual loop detectors to identify and correct for inaccurate spacing between the paired detectors. Finally the methodology is evaluated by comparing the loop detector speeds against the concurrent velocities from a GPS equipped probe vehicle. While the focus of this paper is on loop detectors, with only minor modification the algorithm should also be applicable to other detector technologies that emulate loop detector operation, e.g., side‐fire microwave radar.

Select this Article		Numerical Modeling of Water Levels on Pavements under Extreme Rainfall Philipp Staufer, Marko Siekmann, Sandra Loos, and Johannes Pinnekamp Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000373 Posted ahead of print 9 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract This study presents an advanced model for calculating water levels on impervious areas. The approach combines information about rain intensity and flow condition to dynamically determine overland roughness values. When water levels on profiled surfaces of less than 500 m are calculated, the full dynamic wave approximation is necessary because the transition of flow differs compared to kinetic wave theory at the beginning of the runoff event. The application of the model to a civil airport demonstrates how the frequency of critical water levels changes when cutting of grooves into the runways is considered. The local storm water characteristics are defined by heavy convective precipitation during summer. A critical event was presumed when the water level may cause aquaplaning. The results present a reduction of the number of critical events during a period of 10 years by 68%, even without recognizing the additional friction by the grooves. If increasing friction was included, the remaining frequency would be 0.2 times per year.

Select this Article		Incorporating Priority Preferences into Pavement Maintenance Programming J. Farhan and T. F. Fwa, M. ASCE Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000372 Posted ahead of print 9 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract Traditionally, it has been a common practice to apply priority weights to selected parameters in the process of optimal programming of pavement maintenance. However, there are several issues associated with this approach of incorporating priority preferences into pavement maintenance programming. For instance, applying priority weights to selected problem parameters will lead to a sub‐optimal solution with respect to the original objective function (such as minimal total maintenance cost or maximum pavement condition). The decision maker may not be aware of this consequence and the magnitude of loss in optimality caused by their choice of priority scheme. This paper proposes an improved methodology of incorporating priority preferences into pavement maintenance programming to overcome these problems. Instead of applying priority weights directly into the mathematical formulation of maintenance programming, priority preferences are handled in two stages of post‐processing of the optimal programming process, namely a tie‐breaking analysis and a trade‐off analysis. The optimal programming problem is first solved without applying priority weights to any parameters of the problem. This ensures that the optimality of the solution is not disturbed. In the tie‐breaking post‐processing, prioritized maintenance activities are identified to replace lower priority activities in the solution, without affecting the optimality of the solution. Finally, a trade‐off analysis is performed to introduce more prioritized activities into the solution based on the willingness of the highway agency to accept some loss in optimality.

Select this Article		Large‐Scale Evacuation Using Subway and Bus Transit: Approach and Application on City of Toronto Hossam Abdelgawad, Ph.D. and Baher Abdulhai, Ph.D. Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000371 Posted ahead of print 9 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract Lately, it has been recognized that public transportation systems play a significant role in emergency evacuation. Therefore, this paper is geared toward harnessing subway and bus transit to alleviate congestion pressure during the evacuation of busy urban areas. The routing and scheduling of transit vehicles and subway operation is envisioned as a new variant of the well‐established Vehicle Routing Problem (VRP). The presented model combines multiple variants of the traditional VRP while reflecting on the operational characteristics during emergency evacuation to include: Multiple Depots to better distribute the transit fleet, Time Constraints to account for the evacuation time window, and constraints for Pick‐up and Delivery locations of evacuees. The evacuation problem is hereafter defined as a Multi‐Depot Time Constrained Pick‐up Delivery Vehicle Route Problem (MDTCPD‐VRP). A framework, using Constraint Programming and Local Search methods, is developed to model and solve the problem. An Optimal Spatio‐Temporal Evacuation (OSTE) model is performed first to optimize the evacuation of the background vehicular traffic, generating transit travel cost (i.e. link travel times) as an input to the MDTCPD‐VRP. The methodology is applied to evacuate the entire City of Toronto. The results show that the Toronto Transit Commission (TTC) fleet is capable of evacuating the transit‐dependent population (1.34 million) within two hours on average. The 4 subway lines of the City of Toronto carry around 0.62 million people and can evacuate these people in less than three hours on average. The available TTC shuttle buses (1320 vehicles) can evacuate the remainder of the transit‐dependent population (0.72 million) in about 1.5 hour on average.

Select this Article		A Multinomial Logistic Regression Model for Single‐ and Multi‐Vehicle Collisions on Urban US Highways in Arkansas Ghulam H. Bham, M. ASCE, Bhanu S. Javvadi, and Uday R. R. Manepalli Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000370 Posted ahead of print 3 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract Multivariate analysis can be used to identify the effects of several factors on the causes of a crash compared to univariate analysis. This paper uses a multivariate analysis technique, the multinomial logistic regression (MLR) model, to examine the differences in crash contributing factors for six collision types for both divided and undivided highway non‐junctions, given that a crash has occurred. MLR was used to investigate, i) single‐vehicle, and ii) multi‐vehicle collisions, which included: a) angular, b) head‐on, c) rear‐end, d) sideswipe‐same‐direction, and e) sideswipe‐opposite‐direction collisions. The risks associated with different collision types were found to be significantly influenced by various vehicle actions. The risk of sideswipe‐same‐direction collisions was higher while changing lanes and merging on undivided and divided highways. Similarly, while merging, drivers were prone to angular collisions, and when slowing down to rear‐end collisions on undivided and divided highways. On weekdays, higher risk of multi‐vehicle collisions, whereas on weekends, single‐vehicle collisions were found to be statistically significant. The risk of single‐vehicle collisions due to drivers negotiating a curve, driving on a wet road surface, during nighttime, when vision was obscured, avoiding objects on the roadway, and driving under the influence of alcohol was higher compared to other collision types. Based on the results of analysis, it was found that the risk of single‐vehicle collisions was higher on divided and undivided highways compared to other collision types. Further, binary logistic regression model was used to identify the factors that contribute to crash injury severity, given that a crash has occurred. Drivers and passengers who did not wear lap and shoulder belts and drove under the influence of alcohol were involved in serious crash injuries. Drivers involved in a crash on horizontal and vertical curves were prone to severe crash injuries compared to crashes on straight and level roadways. Head‐on and single‐vehicle collisions were found to be at a higher risk for severe injuries compared to other collision types. Additionally, collision types were strongly related to driver behavior (decision making) parameters such as merging, changing lanes, slowing/stopping compared to parameters such as roadway geometry, atmospheric conditions, surface conditions, etc. From these results, the importance of different statistical techniques is evident as the significant variables varied for crash severity and different collision types.

Select this Article		Moisture Susceptibility of Subgrade Soils Stabilized by Lignin‐Based Renewable Energy Co‐Product Sunghwan Kim, Kasthurirangan Gopalakrishnan, and Halil Ceylan Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000097 Posted ahead of print 3 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract Sustainable use of biomass as a renewable source to produce energy can be an alternative solution to the cost of fossil based energy and global warming. Biofuel production from plant biomass produces not only bio‐based energy but also co‐products containing lignin, modified lignin, and lignin derivatives. This paper discusses moisture susceptibility of subgrade soil stabilized by bio‐based energy co‐product containing lignin, aimed at utilization of bio‐based energy co‐product in soil stabilization as a new application area for bio‐based energy co‐product. An experimental test program was conducted to compare the moisture susceptibility of lignin co‐product treated soils to traditional fly ash stabilizer treated soil samples. Combined additive combinations were also evaluated. The laboratory tests for moisture susceptibility evaluation consisted of two types of tests: unconfined compression strength (UCS) tests after “dry” and “wet” conditioning and visual observation of soaked specimens. Results indicate that the biofuel co‐products have excellent resistance to moisture degradation for the Iowa class 10 soil classified as a USCS CL and an AASHTO A‐6(8). Especially, co‐product A with the higher lignin content is more effective in providing moisture resistance compared to co‐product B with the lower lignin content as well as conventional additive (class C fly ash). Moisture resistance comparable to co‐product A could be obtained through the use of additive combinations (co‐product A + class C fly ash; co‐product A + co‐product B).

Select this Article		Lifecycle Cost Minimization and Sensitivity Analysis for Mechanistic‐Empirical Pavement Design Mark McDonald and Samer Madanat Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000346 Posted ahead of print 3 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract Rebuilding and maintaining the nation's highway infrastructure will require very large capital outlays for many years to come. While the expenditures involved in the maintenance and construction of highway facilities are large, current methods of pavement design used in common engineering practice do not routinely take advantage of design optimization methodologies. This paper presents an optimization formulation for mechanistic‐empirical pavement design that minimizes lifecycle costs associated with the construction and maintenance of flexible pavements. Sensitivity analysis is performed on the model to understand how the optimal design changes with respect to variations in the critical design inputs. Using typical values for the costs associated with the construction of each pavement layer and the reconstruction of failed pavement sections, it is determined that extended life flexible pavements may provide significant lifecycle cost savings despite their higher initial construction cost. However, perpetual pavements that control critical strains to levels near the fatigue and endurance limits for the HMA and subgrade soil should be designed only when traffic levels are sufficiently high to warrant them or when sufficient uncertainty exists in the mean values of design input probability distributions. Optimization studies performed under uncertainty have showed that designs for extended life pavements are robust with respect to physical variability in material properties, but are significantly impacted by a lack of knowledge of probability distributions.

Select this Article		GIS Based Rural Road Network Planning for Developing Countries Ajai Kumar Singh, Ph.D. Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000212 Posted ahead of print 23 August 2010 Full Text: \| Download PDF
	+ -	Show Abstract Rural transport and accessibility problems cause isolation, which is one of interlocking dimensions of poverty. Improving rural access to facilities, services and employment opportunities are now emphasized as an effective means towards poverty alleviation. Travel and transport are the means by which people gain access to the facilities and services they need for the everyday life. Distance, time, effort and cost are the measures of the level of access to facilities and if they are too high they constrain opportunities and potential for development. The rural settlements devoid of all weather road connectivity have poor accessibility and thus the immobility of their population. The aims of intervention to improve rural transport should therefore be to upgrade access to facilities to an acceptable level. A well planned road system in rural areas is one of the most important infrastructure elements which improves rural accessibility and contributes to the rural development as a whole. The rural road network planning methodology presented in this research paper is based on accessibility concept and implemented using GIS technology. A new index of accessibility is designed which evaluates various rural road link options for their efficiency in accessing the missing functions in the unconnected settlement. The accessibility based approach of rural road planning offers maximum benefit to the unconnected settlement in terms of access to various facilities or the main road network in a coordinated fashion by maintaining an integrated road system. A GIS based technique for the analysis of alignment of new road link options has been developed which considers the topographic and land use characteristics of the area. GIS‐T software package, TransCAD, is used to organise the database for road alignment and implementation of the developed rural road planning methodology.

Select this Article		Load Transfer Characteristics of Aggregate Interlocking in Concrete Pavement Swati Roy Maitra, K. S. Reddy, and L. S. Ramachandra Journal of Transportation Engineering doi:http://dx.doi.org/10.1061/(ASCE)TE.1943-5436.0000114 Posted ahead of print 2 October 2009 Full Text: \| Download PDF
	+ -	Show Abstract This paper presents a finite element model of a jointed concrete pavement with aggregate interlocking load transfer system. Interlocking mechanism has been modeled by a set of discrete springs. A new parameter ‘modulus of interlocking joint (K_j)’ has been introduced to represent the load transfer characteristics of the interlocked joint. Guidelines have been proposed for the selection of the modulus of interlocking joint as a function of aggregate size and joint opening. Stiffness values for the linear springs can be selected using the modulus value K_j. The numerical model, with the joint spring stiffness values selected from the present guidelines, has been validated with experimental results available in literature.