Title

Warranting Traffic Signals on the Basis of Proximity of Railroad Grade Crossings

Document Type

Journal Article

Publication Date

2007

Subject Area

operations - traffic, infrastructure - traffic signals, mode - rail

Keywords

Warrants (Traffic control devices), Vulnerability assessment, Traffic signals, Traffic lights, Traffic control signals, Simulation, Risk assessment, Railroad grade crossings, Proximity, Probability, Metrics (Quantitative assessment), Manual on Uniform Traffic Control Devices, Level crossings, Highway traffic signals, Highway railroad grade crossings, Highway rail intersections, Grade crossings, Gap acceptance, Computer simulation, Accident exposure

Abstract

There were two concurrent paths in this research. Path 1 estimated the probability, p sub vehicle/train, that a vehicle will be in the train dynamic envelope given that a train arrives. This was done by an extensive simulation effort that included some data collection on relevant gap acceptance patterns. Path 2 identified the exposure factors, selected a risk metric, and established a target or threshold for the risk, which is expressed as an upper bound on p sub vehicle/train. As a result of the investigation, the warrant is based on the principle that the expected fatality rate at the crossing should not exceed rates found at unsignalized intersections. The two paths converged by expressing the constraint p sub vehicle/train ≤ __ (where __ is in terms of traffic terms in common use—e.g., volumes, composition, track location distances). This constraint led to the warrant, which was then validated with data acquired or collected for the purpose. The draft warrant was prepared as a result of the undertaking, was endorsed by the National Committee on Uniform Traffic Control Devices, and is currently in the formal review process, culminating in final edits and a decision on inclusion in the next edition of the "Manual on Uniform Traffic Control Devices."