UC Irvine Institute of Transportation Studies

A traffic signal is a substantially different traffic sign compared with othe traffic devices. The uniqueness of traffic signals is manifested in their displaying an alternate message and not a constant one. The transition period from one message to another creates a decision problem for drivers. An inappropriate decision might create a risk of a rear-end collision. This article presents a disaggregate behavioral model for drivers' decision when the green light ends. It is demans trated, and supported by field data, that a large option zone increases the indecision of drivers. The increase in indecision creates a greater risk of rear-end collisions, as experienced at many intersections. The influence of distance from the intersection and of approach speed on drivers' decision is examined through the model.