Distributions for Gaps in Road Traffic

Publisher Website
Google Scholar
Abstract
The importance of both counting and gap distributions in road traffic flow has been recognized for some years. One reason for their importance is that they are linked to three important aspects of road traffic viz. flow, concentration and capacity. The flow-rate is the reciprocal of the mean time-gap between vehicles and concentration is the reciprocal of the mean distance-gap between vehicles. Capacity is, in one sense or another, the maximum flow, and is thus related to the minimum time-gap between vehicles. Another reason for the importance of these distributions is that the distribution of vehicles on a road can be considered as a succession of moving gaps and dealt with on that basis. The displaced exponential distribution has been known for some time to be a reasonably good model for low-medium flow-rates of up to about 800 vehicles per hour (v/h) in one lane, but it breaks down for higher flows. A number of alternatives to the displaced exponential are considered in this paper. A substantial amount of data, collected in New Zealand, has been used in fitting the distributions. There is no real evidence to show that the displaced exponential can be improved upon much as a model, although overall the use of a mixed exponential improves the fit somewhat. However, all the alternative distributions are easy to sample from, and can be used in simulation studies.

This publication has 0 references indexed in Scilit: