Probabilistic approach to implementing traffic signal warrants

Traffic signal warrants documented in the Manual on Uniform Traffic Control Der ices neglects the effect of daily and hourly volume variations in traf fic. Furthermore, current practice cannot be used to prioritize signal inst allations among multiple intersections that meet the warrants. Finally, the re is no guidance in the Manual on Uniform Traffic Control Devices on how t he warrants can be applied to projected traffic conditions when hourly coun ts are not available. This paper describes a probabilistic approach to impl ementing traffic signal warrants. The proposed approach used Monte Carlo si mulation to generate, on the basis of variable hourly traffic counts, the p robability that any particular signal warrant will be met at an intersectio n. The simulation approach was extended to develop planning level guideline s for signal installation using predefined synthetic traffic flow profiles and the average daily traffic estimates for the intersecting streets. The p roposed guidelines were compared with current planning guidelines used in T exas and California. The comparison results indicate that the Texas guideli nes tend to underestimate the need for traffic signal installation, whereas the California guidelines tend to overestimate the need.