Journal of Transportation Engineering, Part A: Systems

When a traffic incident occurs, congestion starts to disseminate around the incident location. Considering a suitable area to assess the impact of incidents and develop traffic network prediction models for evaluating traffic management schemes remains a challenging question. This study aims at developing a modeling framework to identify an affected area around the incident. For this purpose, linear regression models are presented to predict the maximum distance from a closed link to a link with a specified expected increase in travel time. Nine different models are presented to investigate the effects of the network topology and demand on the size of the affected area around the disruption. The models demonstrate that traffic volume on the closed link, a link’s area type, and the travel time on the first and second alternate paths with lowest travel times predict the radius of the affected area. This study will help traffic network managers reduce the complexity of their models by allowing them to use a subnetwork instead of the entire network.

To respond to funding shortages and sustainably preserve their aged pavements, transportation agencies are forced to go beyond conventional thinking to develop innovative, cost-effective pavement preservation methods to stretch their limited funding. In 2007, the Georgia Department of Transportation (GDOT) developed a new pavement preservation method using micromilling in conjunction with a thin overlay to cost-effectively replace a porous asphalt layer without replacing or damaging the underlying dense-graded or gap-graded asphalt layer. The new method was applied on two large-scale projects, one in 2007 on I-75 that was approximately 150.6 lane-km, and another in 2011 on I-95 that was approximately 135 lane-km. These projects saved more than $10 million (approximately $37,092 per lane-km). Because of the successful implementation of the new pavement preservation method, GDOT has worked with Georgia Institute of Technology and contractors to standardize the new procedures, including applying pretreatment of the areas with distresses deeper than micromilling depth, determining the specifications for using variable micromilling depth to remove the porous layer completely and ensure the quality of the milled surface, developing a stringent requirement using a new performance indicator [ridge-to-valley depth (RVD)] to quantitatively measure the micromilled pavement texture to ensure its quality, and developing an automatic quality control method using a road laser profiler retrofitted to provide timely feedback to the contractors immediately after micromilling. This requires a contractor to adjust the milling operation if necessary, including the milling machine speed and the milling drum rotation frequency, and to conduct an inspection of machinery teeth, among other things, to achieve a productive milling speed while meeting the RVD requirement. This paper provides the details of this new method, including the challenges, the construction procedures, and the lessons learned in the course of the projects, which are especially valuable for transportation agencies to explore as they consider alternative pavement preservation methods that can cost-effectively preserve their aged pavements.

To support scientific planning and management of transportation systems, this paper carries out comprehensive stated preference (SP) surveys to investigate commuters’ mode choice behavior in multimodal networks. Efficient scenarios are designed using the utility-balance principle to incorporate four commonly used commuting modes and four decisive factors influencing mode choices. Random parameter logit (RPL) models are used to estimate commuters’ willingness to pay (WTP) quantitatively and explore preference heterogeneity. In particular, the potential factors yielding heterogeneity in valuation of travel time reliability (TTR) and in-vehicle crowding are identified. The results indicate large heterogeneities in WTP for TTR improvement and in-vehicle crowding reduction. Demographic attributes (age and education), commuting distance, and time schedule variables (flexible work time and departure time constraints) could partially explain travelers’ heterogeneity in WTP for TTR. Age, gender, income, and education levels are identified as having significant influences on WTP for reducing in-vehicle crowding. This study provides useful references for transport demand forecasting and implications for transport policy-making in a multimodal network.

The comprehension of network-level consequences resulting from disruptive events is a main gray area in the evaluation of transportation network resilience at the regional level. Explaining hazard impacts on regional network infrastructures and identifying significantly affected areas are important for communicating the need for building resilient infrastructure. This paper presents a framework for assessing the regional network resilience by leveraging scenario-based traffic modeling and GIS techniques. High-impact-zone location identification metrics were developed and implemented in preliminarily identifying areas affected by bridge closures. Resilience was estimated, and an index developed by utilizing practical functionality metrics based on vehicle distance and hours traveled. These are illustrated for the Tampa Bay, Florida, area. Findings for 10 bridge closure scenarios and recovery schemas indicated significant regional resilience losses. The I-275 bridge closure indicated the highest functional loss to the regional network: the aggregated resilience index below 0.5 reflects severe network performance deficit and mobility limitations.

Vehicle platooning is an innovative strategy that uses automated driving technology and communication to enable a more efficient use of transportation networks. By controlling tighter gaps between vehicles, vehicle platooning will increase freeway capacity. However, it is important to quantify the extent of the increase of capacity so that highway engineers can plan for this technology. This Federal Highway Administration research develops an analytical model to predict the capacity of basic freeway segments based on the market penetration and the maximum number of vehicles allowed in a platoon. It uses these predictions to calculate passenger car equivalents, which may be required for planning purposes. Simulations show that capacity can be predicted analytically to within 2% of simulated values. In addition, for the parameters used in the analysis, the capacity of freeways that restrict platoons to no more than 5 vehicles is comparable to the capacity of freeways that allow larger platoons (e.g., 6.1% maximum difference in capacity between maximum 5 and 12 vehicle platoons); consideration of limiting platoon size is important to ensure maneuverability.

This research work puts an emphasis on passenger car unit (PCU) estimation using different methods on eight-lane divided urban multilane roads using a well-calibrated and validated microsimulation model. In this context, at first, three methods were applied for PCU estimation and were checked for its accuracy, which are: (1) PCU estimation using the TRRL (Transport Road Research Laboratory, UK) definition; (2) PCU estimation using the speed–area ratio concept; and (3) PCU estimation using a newly proposed methodology in this study, which is based on an area occupancy–based matrix solution of simultaneous equations developed between a mixed-traffic scenario and an all-cars traffic scenario. The PCU equivalent flow using three methods, compared with the all-cars scenarios at different flow levels, resulted in mean absolute percentage errors (MAPE) of 6%, 12%, and 7%, respectively. Subsequently in this study, a new concept of homogeneous equivalent is also proposed, which directly converts heterogeneous flow into a homogeneous equivalent using the area occupancy value of a mixed-traffic stream. The concept is tested over varying traffic compositions and different traffic volumes and resulted in a MAPE of 8 to 18%. The output from the present study may be useful to traffic engineers, researchers, and practitioners for getting equivalent flow on different uninterrupted facilities, using this simplified yet scientific methodology.