Conclusions
ATS is affected by traffic composition and other geometric condi- tions. Even though it is a good performance measure in terms of road users’ perception, it is not suggested by traffic engineers because it lacks a reference point for comparison across locations. For devel- oping countries, where the passenger cars proportion is low, ATSPC and A TSPC=FFSPC are not suitable LOS measures because they can- not represent the total traffic stream conditions. PF, which is sug- gested by HCM (TRB 2010) as a surrogate measure for PTSF, is found to have a very weak correlation with traffic volume. Because the present study is conducted under mixed traffic conditions, vehicles are considered to be following when they are traveling with a gap less than 2.6 s. Newly introduced performance measure NF showed a strong relation with traffic volume. However, this param- eter alone is not able to truly explain the congestion conditions on a road. NFPC is considered because it would explain the quality of traffic flow in a better way. A statistically strong correlation is developed between NFPC and traffic volume. Threshold values of different LOSs are assigned correlating NFPC with PTSF ranges suggested by HCM 2010. These limits will help traffic engineers in analyzing the performance of two-lane rural roads in India.
The limits of PTSF as given in HCM for LOSs A and B seem to be quite high. In the HCM (TRB 2010), LOS A is taken up to a volume level where 35% of the vehicles move in the following state. It contradicts the definition of LOS A where vehicles are as- sumed to be moving freely at their desired speed. Similarly, limits suggested for LOS B (35–50%) are also quite high. On the other hand, the limits of NFPC for LOS A and B obtained from this study seem to be quite logical. However, this new performance measure
needs to be checked with respect to other classes of two-lane interurban highways in India.