Incidents and fatalities at highway-rail grade crossing in the United States have declined significantly over the past two decades despite a significant increase in both train and vehicle traffic. Therefore, to provide a more realistic comparison of safety performance over the years, it is important to include both train and vehicle traffic when calculating incident rates at highway-rail grade crossings. The U.S. Department of Transportation’s (USDOT) Federal Railroad Administration (FRA) tasked the USDOT Research and Innovative Technology Administration’s John A. Volpe National Transportation Systems Center (Volpe Center) to review an exposure metric called traffic moment (TM), which is currently used by European nations, and to apply it to U.S. data. Historically, the highway-rail grade crossing incident rate is calculated in terms of train miles travelled (TMT). Although it is a useful measure of the exposure to the risk of collision between train and motor vehicle, adding vehicle exposure would reflect a more accurate picture. TM is generally calculated as the product of the average value of highway traffic and the average value of the train traffic. Figure 1 graphically displays the TM concept, where AADT stands for average annual daily traffic and TTPD stands for total trains per day. TM could be defined as the maximum number of encounters between trains and motor vehicles based solely on the average frequency of train and motor vehicle traffic. The Italian Ministry of Transport and the Italian State Railway defined TM as ?a numerical value that is a function of the average value of highway and train traffic through the grade crossing? [1]. The Volpe Center study was conducted in two parts: (1) incidents per TM were calculated for public crossings from 1989 to 2008 to compare safety performance at highway-rail crossings against traditional methods by using TMT; and (2) a comparative analysis of public highway-rail grade crossing safety performance between active and passive crossings for the same period of time. (Author/publisher)
Abstract