A STUDY ON LOS PARAMETERS FOR TWO-LANE ROADS IN MIXED TRAFFIC

Abstract

The traffic performance of a highway is expressed in terms of level of service (LOS). It is a major input to important decisions on public fond investments that arc made at different stages of the highway life. The evaluation of traffic performance on two-lane highways in not ,in easy task because of its unique operational characteristics. The objective of this research is to examine the applicability of various performance measures for two-lane roads under mixed traffic conditions and to assign threshold values for different levels of service based on the best performance measure observed. For this study, six most popular performance measures were considered and traffic data collected on 3 sections of two-lane roads was used to study the effect of traffic volume on these performance measures. Graphical and statistical analysis was carried out among the performance measures and traffic volume. Among the performance measures evaluated no measure was found reliable for mixed traffic conditions. Therefore the number of followers (Ni:) was introduced as a new performance measure. Followers in mixed traffic are defined as vehicles travelling with gap less than 2.5 s. Although NF is found to have good correlation with flow rate, it was not able to reflect the congestion conditions of a roadway. Therefore this parameter was further modified to number of followers as a proportion of capacity (NFPC). It demonstrated a very strong relationship with traffic volume. 'l'hrcshold values are proposed for different LOS based on NFPC for mixed traffic conditions