Differences in Expressway Traffic Characteristics and Optimal Service Flow Rate on Sunny and Rainy Days

Abstract:

This paper investigates the analysis method of the optimal service flow rate of the expressway on sunny and rainy days. First， the distribution characteristics of flow， speed， and occupancy rate on rainy and sunny days are analyzed using coil loop data. Then， the K-S test is used to confirm the significant difference in traffic flow on sunny and rainy days. The capacity and the bottleneck breakdown analyses are performed on rainy and sunny days， respectively. It is shown that the V/C calculated according to the current standard does not apply to the analysis of the level of service （LOS） of rainy-day traffic flow， and there is a limitation in emphasizing the maximum throughput and inaccurate information after the bottleneck breakdown. Therefore， this paper proposes an academic idea of maximizing the service traffic volume while taking into account a certain operating speed and provides the concept of optimal service flow rate and its determination method. It， then， establishes a three-dimensional K-means clustering model with integrated flow-speed-occupy to obtain the traffic state clustering results before and after breakdown on rainy and sunny days. The results explain the relationship between service flow rate and LOS before and after breakdown， and point out that the pre-queue transition flow can be used as the optimal service flow rate.

Key words:traffic capacity;optimal service flow rate;three-dimensional K-means clustering model;urban expressways;weather conditions