Conflicts and delay studies at unsignalized intersections.

This paper describes simulation models for both unsignalized intersections and signalized intersections. The number of conflicts and the number of vehicle delays are used to evaluate the level of service of unsignalized intersections; the number of conflicts is used to evaluate safety effects, and delay is used in cost-benefit analysis. A formula for calculating the number of conflicts at unsignalized intersections was derived, and it is found to agree reasonably well with simulated results. Signalized intersections were also simulated to find out the number of conflicts and the vehicle delays occurring there; this was done in order to determine the traffic volume at which traffic signal control should be considered for an unsignalized intersection. The following conclusions are reached: (1) for both unsignalized and signalized intersections, the number of conflicts and delays increases as traffic flow increases; (2) when an unsignalized intersection is signalized, the number of traffic conflicts there decreases, while the delay increases; (3) at an unsignalized intersection, the total number of conflicts depends very much on the assignment of the total volume to the two intersecting roads; (4) the decision whether to signalize an unsignalized intersection should be based on safety evaluation; (5) when the total volume for an unsignalized intersection is at least as great as its critical volume, the intersection should be controlled either by police or by traffic signals.