Identification of Optimal Left-Turn Restriction Locations using Heuristic Methods

Restricting left turns throughout a network improves overall flow capacity by eliminating conflicts between left-turning and through-moving vehicles. However, doing so requires vehicles to travel longer distances. Implementing left-turn restrictions at only a subset of locations can help balance this tradeoff between increased capacity and longer trips. Unfortunately, identifying exactly where these restrictions should be implemented is a complex problem because of the many configurations that must be considered and interdependencies between left-turn restriction decisions at adjacent intersections. This paper compares three heuristic solution algorithms to identify optimal location of left-turn restrictions at individual intersections in perfect and imperfect grid networks. Scenarios are tested in which restriction decisions are the same for all intersection approaches and only the same for approaches in the same direction. The latter case is particularly complex as it increases the number of potential configurations exponentially. The results suggest all methods tested can be effectively used to solve this problem, although the hybrid method proposed in this paper appears to perform the best under scenarios with larger solution spaces. The proposed framework and procedures can be applied to realistic city networks to identify where left-turn restrictions should be implemented to improve overall network operations. Application of these methods to square grid networks under uniform demand patterns reveal a general pattern in which left turns should be restricted at central intersections that carry larger vehicle flows but allowed otherwise. Such findings can be used as a starting point for where to restrict left turns in more realistic networks.

The issue of supply model update in the microscopic traffic flow simulation for the Poznan agglomeration

The development of MATSim scenario for the Poznan agglomeration has revealed some weak points in so far approach to creating road network model and its use in simulation. Decision was made to change approach toward incorporating turn restrictions into model (with use of MATSim Lanes extension) and automating update process from OSM data. A special verification and conversion algorithm has been developed, implemented and assessed. The most important aspects of this process has been presented in this paper.

A case study of combined winter road snow plowing and de-icer spreading

In this article, we address a winter maintenance problem where the streets need to be plowed and gritted in a sequence that depends on the class of the road. The maintenance fleet includes vehicles equipped for plowing, some for spreading, and some for both at once. The objective is to complete the operations as rapidly as possible while considering street hierarchy, turn restrictions, heterogeneous speeds, and street–vehicle compatibility. An adaptive large neighborhood search framework is developed to solve the problem. Analysis of the results obtained can provide both a good basis for vehicle routing and help managers plan long-term policies and investments.

Effective Measures to Restrict Vehicle Turning Movements

This study evaluated alternatives to raised and nontraversable medians on driveways and approaches. Raised medians are often effective for limiting direct left turns at significant conflict points. Raised medians also improve corridor aesthetics. This research reviewed a variety of turn restrictions to determine how effectively they address the operational needs of the transportation network while addressing contextual sensitivities. The turn restrictions evaluated in the study were separated into three broad categories: turn restrictions located only at the access point, turn restrictions located only in the roadway (typically some type of median configuration), and combined turn restriction configurations. Field evaluations in Oregon and Texas were performed to determine the effectiveness of various turn restriction configurations. In addition, microsimulation evaluations were used to identify the operational impacts of the various turn maneuver restrictions.

RESEARCH ON THE LAYERING A* ALGORITHM FOR REAL-TIME NAVIGATION

According to the existing problems in the applications of embedded navigation, this paper designs the hierarchical search A*algorithm, based on the transferring road network, to meet the need of real-time navigation. In the algorithm, a hierarchical search strategy is applied to route programming of large area, yet the duplicate searching A* algorithm, based on the transferring road network, is applied to the path computation, which is able to handle intersection turn restrictions and node weight, with little storage space but fast searching speed. Practically, the algorithm is proved to meet the technological need of real-time navigation both in computing speed and route rationality.