Journal of Transportation Engineering, Part A: Systems

An active traffic management (ATM) system was activated on Interstate 66 (I-66) in northern Virginia in September 2015. The ATM system included advisory variable speed limits (AVSLs), lane-use control signals (LUCS), and dynamic hard shoulder running (HSR). This paper quantifies the operational and safety effects of the ATM system on I-66 using approximately 2 years of crash and operational data following system activation. The operational analysis showed that off-peak hours experienced significant travel time improvement after the ATM system was activated, but peak periods in the peak direction of travel generally did not see improvement. Further analysis revealed that most of these improvements occurred on the HSR sections. The safety evaluation results showed 4%, 4%, and 6% reductions in total (all severity), multiple-vehicle (all severity), and rear-end (all severity) crashes, respectively, across the entire corridor. Segment-level analysis again showed that the most safety benefits were observed at locations with HSR (31%–38% crash reductions), and no significant reductions were found on the sections with only AVSLs and LUCS.

A newly proposed unconventional intersection design, exit lanes for left-turn (EFL) intersections, has been demonstrated to be very promising for capacity improvement. However, the difference in saturation flow rates at EFL intersections compared with conventional intersections and the influencing factors remain unknown. In this paper, a saturation flow rate adjustment model for EFL control is developed and calibrated based on field data. Five influencing factors, namely the median opening blockage, demand starvation, multilane interference, conflict with opposing vehicles, and lane changing, are considered. The accuracy of the model is validated using nonparametric tests. Results show that the reduction in saturation flow rate for the normal approach left-turn lanes, the left-turn lanes in the mixed-use area, and the left-turn lane at the prestop line caused by EFL control are 6%, 31%, and 19%, respectively. The key impact factors for the saturation flow rate at the main-stop line and the prestop line are the demand starvation (16% reduction) and lane changing (16% reduction), respectively. This research provides guidelines for planning, design, and operation of EFL intersections to prevent negative effects while retaining their efficiency.

This paper develops a track allocation model for large railway stations based on stochastic schedules, which considers balanced utilization as well as minimum occupation time of station tracks. The stochastic schedule is represented by the mean and variance of both train arrival and departure times. Due to the nondeterministic polynomial completeness of the track allocation problem, a tailored simulated annealing algorithm is developed to solve the proposed model. In addition, a numerical case from the Baoji railway station is studied that demonstrates the model’s performance. After solving the model, the results of track allocation schedule can detect the limited carrying capacity area in the station, and the capacity relationship of two station bottleneck sections can be obtained. The capacity of the left station bottleneck area is about 1.48 times higher than that in the right station bottleneck area in Baoji railway station.

Several traffic modeling tools are currently available for evacuation planning and real-time decision support during emergencies. This paper reviews potential traffic-modeling approaches in the context of wildland–urban interface (WUI) fire-evacuation applications. Existing modeling approaches and features are evaluated pertaining to fire-related, spatial, and demographic factors; intended application (planning or decision support); and temporal issues. This systematic review shows the importance of the following modeling approaches: dynamic modeling structures, considering behavioral variability and route choice; activity-based models for short-notice evacuation planning; and macroscopic traffic simulation for real-time evacuation management. Subsequently, the modeling features of 22 traffic models and applications currently available in practice and the literature are reviewed and matched with the benchmark features identified for WUI fire applications. Based on this review analysis, recommendations are made for developing traffic models specifically applicable to WUI fire evacuation, including possible integrations with wildfire and pedestrian models.

Safety issues along urban expressways have gained increasing attention for their direct impact on traffic operation, especially after a substantial amount of reconstruction work that altered the cross section designs to create additional travel lanes. Despite the obvious benefit of higher capacity, the safety effects related to the variety of lane widths are uncertain. This paper examines the impact of lane widths on crash frequency for various types of crashes based on field data obtained from the expressway system in Shanghai. Four data sets were manually collected, including crash data, traffic flow data, lane width data, and geometric design data. Based on these data, safety performance functions (SPFs) were developed using negative binomial regression models. Crash modification factors (CMFs) were built upon the SPFs to quantify the impact of various lane widths on crash frequency for each crash type of interest. Specifically, we considered five cases in this paper: total crashes, two-vehicle crashes, multivehicle crashes, crashes under congested flow conditions, and crashes under noncongested flow conditions. In addition, lane width data are grouped into three categories in our models: undersized lanes (average lane width $\le 3.25\mathrm{m}$), standard-sized lanes (average lane width around 3.45 m), and oversized lanes (average lane width $\ge 3.75\mathrm{m}$). The standard-sized lanes are always found to have the lowest crash frequency among all five cases; both undersized and oversized lanes are found to increase crash frequency, that is, total crash frequency for undersized and oversized lanes increased by 1.9 times and 1.34 times, respectively.

Under a limited priority situation, U-turning vehicles attempt to accept smaller gaps, which compels approaching through vehicles to slow down and experience delays. Delay within the median opening area is termed median delay, which is studied in two parts: Median delay 1 (from start to center of median opening), and Median delay 2 (center to end of median opening). The significant difference between these two delays is established by a t-test. The effect of U-turning volume on Median delay 1, Median delay 2, and total median delay is studied. Considering the lateral movements of approaching through vehicles within the median opening area, the effect of the zone on median delay is studied. Furthermore, the effect of the category of U-turning vehicle on median delay is examined. Finally, three mathematical models are proposed considering the effect of (1) U-turning volume, (2) zone through which the vehicle is moving within the median opening area, and (3) category of U-turning vehicle. The proposed models are validated by comparing the model values with the field data.