IMPACTS OF TRAFFIC SIGNAL INSTALLATION AT MARGINALLY WARRANTED INTERSECTIONS

This report documents the development of guidelines for the decision whether to install a traffic signal at a marginally warranted intersection. The recommendations are based on field and simulation studies of a number of intersections across Texas which were identified as marginally warranted by various Texas Department of Transportation (TxDOT) districts. The research included both delay and accident studies. The TEXAS simulation model was used for the delay studies. Eight different intersection geometries and twelve generic 24-hour volume patterns representing marginally warranted conditions were simulated. Each combination of intersection geometry and volume pattern was simulated as a two-way stop, an all-way stop, and an actuated traffic signal. Safety studies considered the frequency of accidents by severity and accident type. Five years of accident data were analyzed at each of the seventy-two marginally warranted intersections across the state. The intersections were classified into six groups, namely, low-speed rural, low-speed urban, high-speed rural, high-speed urban, rural by population, or rural by MUTCD definition. The simulation results showed that in all cases studied, actuated traffic signals yielded significantly greater delays than two-way stops, and all-way stop control generated significantly greater delays than actuated traffic signals. However, in one out of the six intersection categories, namely low-speed rural conditions, signalization showed the potential to significantly reduce certain types of accidents.