Safer and better intersections

Intersections can be priority (Yield, Stop, Four-way Stop, Mini-circle and Roundabout) or traffic signal controlled. Each priority type or traffic signal setting has a different and often critical effect on traffic flow, capacity, delay and safety. While traffic signal warrants are available, there are no official guidelines for when to consider other control devices such as roundabouts, and even if a signal is chosen, there is little or no guidance for deciding whether or how many flashing stages would be optimal, how many lanes are needed and what road markings are best. This paper introduces the principles that need to be considered when making these complex decisions. When the paper is presented to the audience, a software program called AutoJ will be demonstrated. It will be shown how the program can be used to choose the optimal control device (warrant), how delay, volume/capacity, queue and level of service is calculated and how signal timings and diagrams are instantly produced.