Traffic simulation using the Intelligent Driver Model : a study of the impact of safe distance on traffic flow

Abstract: Due to increasing demands on transportation, traffic congestion has become an increasingly common problem. It brings consequences such as increased travel time and profound negative effects on health and environment. One of the leading causes of traffic delays and queue formation occurs when drivers make imperfect speed adjustments in relation to the vehicle in front. If enough vehicles occupy the road, these imperfect speed adjustments can cause ripple effects throughout the system which reduces average speed and traffic flow. This is why drivers should aim to use safe distance as it dampens the effect of imperfect speed adjustments by providing space from the car in front, a sort of buffer. The aim of this report was to investigate the impact of varying safe distance on traffic flow by defining safe distance as a time delta from the vehicle in front, instead of a fixed distance. A traffic simulator was used and iterated upon, based on the Intelligent Driver Model, and simulations were run with varying speed limits and safe distance. Two different scenarios were studied: a temporary obstacle completely blocking a one-lane road, and a reduced speed zone at the end of a one-lane road. The results indicated that shorter safe distances may lead to higher vehicle throughput, but not necessarily better traffic flow since it consistently led to increased queue formation when examining average vehicle speed, maximum congestion and stopped time.