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Left turns may generate efficiency problems, which can be solved by appropriately prohibiting left turns. The goal of this paper is to propose a method for purpose of minimizing total travel times in urban road networks by prohibiting left turns. With left turn prohibition, the signal timing plan is optimized with the lane-based method because the method can adequately handle both signal timing optimization and lane assignment. The total travel time is calculated with link flows and link travel time being estimated with signal settings. As illustrated by numerical examples, prohibiting left turns reduces the total travel time of car traffic in road networks. As the left turn prohibition results can handle the randomness in the network, these results provide potential implications for congestion management.

Recurring congestion at signalized intersections is caused by the inability of traffic signal controls to serve demand even in cities where advanced traffic signal timing and management systems are in operation. Left-turn prohibition (LTP) and partial grade separation with low-clearance underpass (LCUP) are possible congestion mitigation actions for urban complex and congested signalized intersections that have exhausted other options for capacity enhancement, such as lane addition and signal timing optimization. LTP and LCUP improve traffic signal efficiency by eliminating signal phases, increasing green splits, or adding lanes. They also improve intersection safety by eliminating certain conflicts. At the same time, they necessitate traffic rerouting, may have negative impacts at downstream locations, and may have perceived or actual impacts to accessibility and neighborhood character. A planning-level assessment method to quantify and compare the benefits and costs LTP and LCUP was developed to...

Left turns generate safety and efficiency problems in urban road networks. Prohibiting left turns is one solution to handle left turn problems, but previous studies did not pay much attention to detour analysis after left turn prohibition. As communication between infrastructure and vehicles influences detour choice, the goal of this paper is to determine which left turns should be prohibited at one intersection in a grid network by maximizing the reserved capacity in communication scenarios. The problem was formulated as Mixed Integer Linear Program which was solved by IMB ILOG Cplex. Prohibiting left turns increases reserved capacity if the adjacent intersections are not congested. The reserved capacity in the communication scenario proves a positive effect on the performance of the intersection.

In order to set left-turn prohibition measures rationally, left-turn prohibition measures installation warrants at unsignalized intersection are discussed. While the analyses on conflict characteristics generation mechanism and different detour types of left-turn traffic are also described in this paper. We define conflict points as the sum of the two convergent traffic volume and establish intersection conflict points calculation model before and after taking left-turn prohibition measures. Then the conflict points variation value is taken as left-turn prohibition evaluation standard. If the variation value decreases after setting left-turn prohibition measures, we believe the measure is feasible; Otherwise, it is not suitable. Then an example is presented as verification which showing good results. The research will provide a basis for the implementation of left-turn prohibition measures at unsignalized intersections and improve its traffic efficiency.

Urban road networks may benefit from left turn prohibition at signalized intersections regarding capacity, for particular traffic demand patterns. The objective of this paper is to propose a method for minimizing the total travel time by prohibiting left turns at intersections. With the flows obtained from the stochastic user equilibrium model, we were able to derive the stage generation, stage sequence, cycle length, and the green durations using a stage-based method which can handle the case that stages are sharing movements. The final output is a list of the prohibited left turns in the network and a new signal timing plan for every intersection. The optimal list of prohibited left turns was found using a genetic algorithm, and a combination of several algorithms was employed for the signal timing plan. The results show that left turn prohibition may lead to travel time reduction. Therefore, when designing a signal timing plan, left turn prohibition should be considered on a par with other left turn treatment options.

The direct left turn at intersections increases delays and causes more accidents in certain conditions. Prohibiting left turns could increase the capacity of the road network and reduce the delays. This research aims to analyze which left turns should be prohibited in an urban road network to increase efficiency. Stochastic User Equilibrium (SUE), with left turn prohibition, is studied in this paper, by minimizing the travel time of the network. The left turn prohibition solution, the corresponding cycle time and green times are determined. A left turn prohibition filtering algorithm (LTPFA) is developed in this paper. The core of the algorithm is that the minor left turn flows have priority to be prohibited. The LTPFA succeeds to find optimal or near-optimal result of travel time in the shorter time compared with enumerating all left turn prohibition combinations. As the total traffic demands increase, the traffic network can benefit more from the left turn prohibition.

This study analyses intersection configuration design elements associated with traffic-related air pollution and ranks the three most effective configurations. An assessment methodology for pedestrians PM2.5 exposure associated with crossing traffic hotspots is presented. The quantitative PM2.5 exposure concentration reduction effects of at-grade intersection design with stretched segment, pedestrian bridge and left-turn prohibition are estimated using a new US Environmental Protection Agency general emissions model: a multi-link dispersion model based on the AERMOD model. The results of the case study show that intersection design using a stretched segment has a reverse effect on pedestrian PM2.5 exposure, while the left-turn prohibition and the pedestrian bridge are environmentally friendly options with lower PM2.5 concentrations. In order of effectiveness, the intersection design types can be listed as pedestrian bridge, left-turn prohibition and stretched segment, based on the pedestrian PM2.5 exposure index. This study proposes guidelines and tools that road/intersection designers and engineers can use for quantifying environmental impacts. It also shows that design configurations have the potential to mitigate air quality impacts from traffic.

Urban road networks may benefit from left turn prohibition at signalized intersections regarding capacity, for particular traffic demand patterns. The objective of this paper is to propose a method for minimizing the total travel time by prohibiting left turns at intersections. With the flows obtained from the stochastic user equilibrium model, we were able to derive the stage generation, stage sequence, cycle length, and the green durations using a stage-based method which can handle the case that stages are sharing movements. The final output is a list of the prohibited left turns in the network and a new signal timing plan for every intersection. The optimal list of prohibited left turns was found using a genetic algorithm, and a combination of several algorithms was employed for the signal timing plan. The results show that left turn prohibition may lead to travel time reduction. Therefore, when designing a signal timing plan, left turn prohibition should be considered on a par with other left turn treatment options.