Chapter 22: Modelling Signalized and Unsignalized Junctions

The safe and effective operation of at-grade junctions requires that driver paths be separated in time. Traffic control at junctions enforces this separation either through positive control using traffic signals, or through road laws and established behaviour. This chapter describes the mathematical modelling of driver behaviour to reflect the traffic operations at junctions.

The purpose of modelling junctions is to predict capacities, delays, fuel consumption, and emissions due to the operation of the junction. The modelling can be at a very detailed vehicle by vehicle level and at a broad level. This chapter will discuss methods to predict the capacity and delays. Other performance measures are a function of delays and flows. The chapter is in three parts, the first dealing with definitions, the second dealing with unsignalized at-grade junctions including roundabouts and the third dealing with signalized junctions.