Evaluating the Impact of Grade Crossing Safety Factors through Signal Detection Theory

The purpose of this effort was to apply signal detection theory to descriptively model the impact of five grade crossing safety factors to understand their effect on driver decision making. The safety factors consisted of: improving commercial motor vehicle driver safety through federal regulations, increasing locomotive conspicuity with alerting lights, increasing locomotive conspicuity with reflectors, increasing sight lines, and improving warning device reliability. We estimated d' and β for eight warning devices associated with each safety factor using data from the Federal Railroad Administration’s Highway-Rail Grade Crossing Accident/Incident database and Highway-Rail Crossing Inventory. We also calculated ω for each safety factor and device type to examine the reliability of each independent variable on grade crossing safety. The analysis indicated that the first four safety factors listed above were generally equally effective in improving grade crossing safety. Warning device reliability (which pertained to active warning devices only) still contributed to improvements in grade crossing safety, but the effects were more muted. Grade crossing devices (and particularly active warning devices) are an important safety tool because they increase drivers’ inclinations to stop, and this bias to stop has a greater impact than improving the driver’s ability to detect the train.