Journal of Transportation Engineering, Part A: Systems

A two-lane highway lane-closure work zone is a unique work-zone type because of its traffic impact. When one lane of traffic is blocked, it is necessary to implement a traffic control strategy to effectively serve bidirectional traffic. In the sense that the right of way is allocated between two directions sequentially, traffic control at two-lane highway work zones is similar to signalized intersection traffic control. In order to analyze the problem, this study proposes two primary methodologies: (1) mathematical capacity and delay functions based on signalized intersection theory, and (2) a microsimulation model calibrated using field observed data. After fine-tuning the parameters, the mathematical functions were able to estimate delays with reasonable accuracy. The models developed in this study were applied in the optimization of a two-lane highway lane-closure work-zone control management plan. The resultant delay-capacity diagrams indicate that for pretimed control, roadway capacity should be maintained at a slightly higher level than the traffic demand, whereas the dynamic traffic control scheme is able to achieve lower delay results than the optimal pretimed signal control.

Decision making about transport infrastructure investment is based on the net impacts and risks to the community. The private sector is often involved in toll road projects, including various schemes to design, build, operate and/or finance the project, either in a partnership with a host government, independently, or in some combination. The cost-benefit analysis of a privately operated toll road requires careful allocation of the project impacts, in order to accurately reflect the net impacts and risks to the community from the host government’s perspective. This study investigated whether alternative assumptions from differing perspectives are valid when toll roads are delivered and operated privately rather than by a host government. The treatments of tolls and other toll road project-related payments were considered from different perspectives. Cost-benefit analysis was conducted for a synthesized toll tunnel project case, by considering alternative treatments of some impacts. That led to the exploration of the analysis outcomes of the treatment of tolls from two perspectives: the toll as a transfer payment and the toll as an end-user cost . Various scenarios were explored, including public versus private operations. The Monte Carlo simulation approach was used to account for the risks of variables in the analysis. The synthesized case study revealed that, for privately operated toll roads, treating toll charges as a transfer payment, and alternatively as an end-user cost, can both be valid approaches but from two perspectives. The analysis outcomes under different perspectives are particularly helpful for making decisions on the basis of the impacts and risks solely from the perspective of the host government. The proposed methodology can be used to examine scenarios other than the ones examined in this study, and it can be very useful in the project evaluations of privately operated toll road projects.

Assessment of transit service improvements such as bus lanes, allowing boarding through all doors, and headway-based holding control requires detailed simulation capabilities. However, because the usage of models advanced enough to simultaneously analyze physical and operational measures has been limited, their validity has hitherto remained low. This paper assesses the implementation of several bus service improvement measures in a simulation model. The paper analyzes the effect of isolated and combinations of measures, and validates the model using field experiment data. The model predicted travel time improvements accurately (1–2% difference), while overestimating some of the headway variability effects. The three tested measures exercised negative synergy effects, with their combined effect being smaller than the sum of their marginal contributions, except for headway-based holding, which exercised positive synergy effects with the two other measures.

Improving operational efficiency and safety on freeway segments has long been recognized as a priority in traffic communities. This study presents a comprehensive variable speed limit (VSL) control model for reducing both travel delays and potential crash risks at freeway work zones. The proposed strategy offers the responsible agency a reliable way to determine reasonable speed limits over the control time horizon in response to traffic fluctuations. The control objective of the proposed system is to minimize total operational cost by using embedded functions to estimate total cost with total travel delay and potential crash rate on the targeted freeway segment. This study used a field site in China for its case study to evaluate the effectiveness of the proposed VSL control system. Based on the experimental results, it was observed that the proposed control model shows promise in reducing average delay, number of stops, and average stopped delay on the studied freeway segment. In addition, simulation experiments for sensitivity analysis indicate that the proposed VSL control model is more effective when driver compliance rate exceeds a threshold of 60% and the user-defined benefit threshold ranges 10–20%.

This paper proposes a microscopic spatial-temporal method to capture the vehicle movement trajectories at an isolated intersection. A bi-objective programming model is presented to minimize the overall delay and emission increment with and without traffic signal by jointly determining the optimal signal timing and speed limit. The proposed method explicitly incorporates the effects of vehicle speed limit, acceleration, deceleration, and signal timing on the overall delay (including the delays caused by traffic signal, acceleration, and deceleration) and emission increment with and without traffic signal control at the intersection.

Successful mapping of concrete crosstie flexural demands to different railroad track support conditions can lead to an improved understanding of crosstie flexural performance and more representative design requirements. Even though the ballast layer typically provides significant pressure distribution variability under concrete crossties, understanding these support conditions is essential for accurately predicting bending moments along the crossties, a useful metric for both design and planning of tamping activities in railroad track. To quantify the influence of support conditions on concrete crossties’ bending moments, laboratory experiments were performed. New and center-cracked concrete crossties were loaded while subjected to different support conditions through the use of rubber pads designed to simulate the ballast support. Results show that bending moments at the crosstie center are quite sensitive and may even be underestimated in current U.S. design practices that do not currently allow for cracking. Additionally, findings indicate that rail seat bending moments may be overestimated in typical design practices. Finally, there was no statistically significant difference between bending moments of uncracked and cracked crossties for the investigated cracking pattern.