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原文传递 Effects of Light Rail Transit on Traffic Congestion.

题名：	Effects of Light Rail Transit on Traffic Congestion.
作者：	CHANDLER, C.; HOEL, L. A.
关键词：	LIGHT RAIL TRANSIT; RAILROAD GRADE CROSSINGS; TRAFFIC CONGESTION
摘要：	Many regions around the United States are considering developing light rail transit (LRT) systems as an alternative transportation mode. LRT has been cited by the Portland Tri-Met transit agency as a way to help influence development by promoting more desirable and sustainable land uses near the LRT lines. Light rail is also generally less expensive to construct and operate than other kinds of rail transit systems. LRT is an attractive option because of its ability to be located in a variety of settings, from tracks on an exclusive right-of-way to shared lanes with cars and trucks in an urban street. There is a great possibility for vehicles to experience additional delays when there is interference by LRT operations, such as in the case of at-grade crossings or due to priority being given to LRT vehicles at signalized intersections at the expense of conflicting turning movements. This study examines the effects of light rail crossings on average delays experienced by vehicles. Using the VISSIM 3.70 computer simulation model, four scenarios were examined: isolated crossings of two-lane and four-lane roads, a case in which light rail transit is located in the median of a street, and a larger network that includes four crossings. The effects of variable traffic volumes and light rail crossing frequencies were studied in the isolated intersection scenarios. The scenario with LRT in the median and the larger network examined the effects of different crossing frequencies as well as full traffic signal preemption. The results of the simulated test scenarios indicate that the average additional delays from light rail transit crossings increase with increasing light rail crossing frequencies and increasing traffic volumes up to the roadway's capacity. As the road enters an over saturated condition, the average total delays continue to increase, but the difference in total delays with and without light rail decreases from the unsaturated condition. Preemption of traffic signals near light rail crossings increases the total delay experienced by vehicles that are in conflict with the light rail crossing, but it tends to improve travel times for the no conflicting movements due to the increased green time. Based on these results, it is determined that traffic volumes at crossings and the frequency of light rail crossings are important variables that affect the average additional delays experienced by vehicles.
报告类型：	科技报告