Assessment of Measure of Effectiveness of Two-lane Roads Under Non-homogeneous Traffic Conditions

One aspect of measure of effectiveness of two-lane road is freedom of passing manoeuvre. Highway Capacity Manual (HCM) use percent time spent following (PTSF) as a measure to evaluate freedom of passing manoeuvre. Several researchers found that PTSF is incompatible with nonhomogeneous traffic conditions. Different follower-related performance measures, namely, percent followers (PF), follower density (FD) and the number of followers as a proportion of capacity (NFPC), Percent Impeded (PI), have been evaluated and a new measure called Stripped Based Follower Density (SFD) is introduced considering driving behavior of heterogeneous traffic condition. Data is collected from 12 two lane roads in Sri Lanka using a 2.5 second time gap suggested as driver perception -reaction time by AASSHTO to identify followers. LOS threshold values for SFD were introduced using K-mean clustering technique and compared with HCM LOS threshold.