Implementing the concept of reliability for highway capacity analysis.

Abstract

ABSTRACT In this paper, a stochastic concept for highway capacity analysis is presented. Instead of constant-value capacities, the capacity of a highway facility is regarded as a random variable. Thus, the stochastic approach provides new measures of traffic flow performance based on aspects of traffic reliability. A methodology for the estimation of capacity distribution functions from empirical data based on statistical methods for lifetime data analysis is introduced. This method is derived for the analysis of freeway capacity. However, it is shown that the stochastic approach is also applicable to intersections. The analysis of data samples from freeway sections in Germany yields that freeway capacity is Weibull distributed with a considerable variance. Based on the stochastic description of capacity, a Monte-Carlo technique is proposed to quantify freeway traffic performance over a whole year. This technique also provides a quantitative assessment for oversaturated conditions