Upon receiving a request to install a traffic signal in a school zone (often following a significant crash), the Indiana Department of Transportation (DOT) performs an engineering study following guidelines in the "Manual on Uniform Traffic Control Devices" (MUTCD). Often the study indicates that installation of a traffic signal is not warranted, and the request is denied. The denials generate additional press coverage and requests for explanations, which are difficult to address because of limited data that quantitatively document the effect of signals on crash rates. To solve this problem, the Indiana DOT contracted with Purdue University through the state-university Joint Transportation Research Program to analyze crash data before and after the installation of traffic signals that were marginally warranted. The results confirmed the appropriateness of the MUTCD warrants. Alternatives to traffic signals for improving safety near schools were presented. Indiana DOT can now cite the research results to demonstrate that a traffic signal is not always the best way to improve safety and that other treatments can be effective at lower costs.
Abstract