Abstract:
Speed is one of the well-known causes for crash. Radius of horizontal curve significantly
affects vehicle speed. Drivers unable to manage speed within a curve can get into accident.
The fatal crash rate in horizontal curve is higher than the straight section. Therefore, safety at
horizontal curve is considered as serious matter of concern. Traditionally, safety is analysed
by speed differentials. The differences in operating speed between successive highway
elements can be used as a measure to evaluate geometric design consistency and safety.
Researchers have studied homogeneous traffic with strong lane discipline to predict vehicle
operating speed in two lane highways. However, Indian traffic operates differently than the
one in western countries due to wide variation in vehicle’s operating and performance
characteristics, and weak lane discipline. However, in India studies to predict operating speed
model for four lane divided road is limited. It motivated authors to develop operating speed
prediction model for four lane divided highway. In this study, car speed data at the center of
seven horizontal curves in a four-lane divided highway have been collected. The 85lh
percentile speeds at five sites are analysed to develop a linear speed prediction model for car.
The developed model depends on curve radius and is validated at two different sites. Results
show that I-value is lesser than 0.2, which confirms the applicability ofthe developed model.
