Abstract
The current preemption method for traffic signals at intersections located near highway-rail grade crossings (IHRGC) is known as the standard preemption (SP). The SP strategy is designed to give priority to the phases which clear vehicles off the railroad tracks as quickly as possible before a train arrives at HRGCs and provides the drivers and pedestrians with a minimum warning time (MWT). However, the SP considers neither pedestrian safety nor system efficiency at IHRGCs. As a result, this may lead to safety and delay problems at IHRGCs. To solve the problems, a state-of-the-art transition preemption strategy (TPS) algorithm, named TPS_DT, is developed in this paper. The new TPS algorithm is designed for corridors with multiple HGRCs that have dual tracks. An urban highway corridor with multiple HRGCs in Lincoln, NE, was selected as the study corridor. A calibrated VISSIM model of the study corridor was used to test the safety and efficiency of the proposed algorithm. The algorithm was coded in VAP, which is an add-on module of VISSIM. A roadway-railway corridor with multiple IHRGC and dual rail tracks in Lincoln, NE, was used as the testbed. The Measurements of Effectiveness (MOEs) used for evaluation include the rate of pedestrian phase cutoffs, intersection vehicle delay, and corridor vehicle delay. It was found that TPS_DT can significantly improve pedestrian safety and reduce vehicle delay at IHRGCs. Furthermore, the effects of train arrival prediction errors on safety and efficiency of the IHRGCs are also analyzed in the paper.
Highlights
Highway-rail grade crossings are locations where a highway and railway intersect at the same level [1, 2]
When an intersection is in the proximity of an highway-rail grade crossings (HRGC), typically defined as being within 200 ft, standard practice in the U.S is to interconnect the railroad signal control equipment and the highway signal control equipment and to use a preemption signal control strategy when a train is approaching the HGRC [3]. ere have been a number of studies focusing on preemption operations of traffic signals at intersections near HRGCs (IHRGCs) [2, 4–8]. e traditional standard preemption (SP) strategy, which is the common practice in the U.S, provides vehicles and pedestrians with a minimum warning time [4, 8]
improved transition preemption strategy (ITPS) was designed and tested in the scenario of a single track and a single HRGC and was only concerned with a single train in the corridor. e Transition Preemption Strategy for Dual Tracks (TPS_DT) is developed for the dual-track environment where multiple trains may be traveling in the corridor in both directions. It is designed for a corridor with multiple IHRGCs and associated HGRCs. e TPS_DT has the same basic strategies as ITPS: (1) improving safety by reducing or eliminating the probabilities of pedestrians being stranded on the crosswalks, (2) assigning more phase time to those nondwell phases, before the SP is activated, and (3) using a generic train arrival time prediction model that was incorporated in the algorithm
Summary
Highway-rail grade crossings are locations where a highway and railway intersect at the same level [1, 2]. E traditional standard preemption (SP) strategy, which is the common practice in the U.S, provides vehicles and pedestrians with a minimum warning time [4, 8] This strategy does not consider the safety and delay at the IHRGC and can lead to the abrupt end of current traffic signal phases including the truncation of pedestrian phases due to variations in train arrival times [4, 8]. Simulation studies [8] have illustrated that ITPS can significantly improve both the safety and efficiency of the intersections near HRGCs. e limitation of the ITPS is that it was tested at a single signalized intersection near a highway-rail grade crossing (IHGRC). It does not consider safety or efficiency at a corridor level or network level. A new transition preemption strategy for dual tracks, referred to as the TPS-DT, was developed for railway-roadway corridors with multiple IGHRCs and a dual-track environment with multiple trains passing in both directions
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