Effect of horizontal curve geometry on vehicle speed distribution: a four-lane divided highway study

ABSTRACT

Poor coordination between geometric elements of horizontal curves can lead to unsafe speed. This study evaluated the effect of horizontal curve geometry on vehicle speed distribution for a four-lane divided highway and developed prediction models for mean speed and standard deviation. Spot speed data of passenger cars (PC), heavy commercial vehicles and light commercial vehicles were collected at 24 horizontal curves. Statistical analysis of the speed data of randomly selected 10 sites revealed PC as the critical vehicle category. Hence, the effects of horizontal curve geometry on PC speed were analyzed and radius was identified as the most influencing parameter. Radius beyond 400 m had similar influence on speed distributions. Appropriate models were developed using regression analysis. Degree of curvature was found as the most significant predictor. Benefits of the proposed models over traditional 85th percentile speed in designing and evaluating horizontal curves for consistency and safety were discussed.

KEYWORDS:

• Speed distribution
• four-lane divided highway
• speed prediction model
• highway safety
• horizontal curves

Acknowledgments

The authors acknowledge the opportunity provided by the 3^rd Conference on Recent Advances in Traffic Engineering (RATE 2018) held at SVNIT Surat, India during 11–12 August 2018 to present this work, which forms the basis of this paper. Authors are grateful to the Indian Institute of Technology Bombay, India for providing the seed grant (Project Code: 13IRCCSG001) to conduct this study. Also, authors are thankful to National Highways Authority of India (NHAI) for providing the plan and profile, Mumbai Nasik Expressway Limited (MNEL) for providing support in field data collection, and Mr. Ayush Tyagi, Mr. Mayank Prakash, Ms. Mounica Nagulapally, Mr. David Thangaraj and Mr. Tushar Choudhari for their support in data collection and extraction. Authors would also like to thank Mr. Apratim Datta for drafting Figure 1. Finally, authors would like to thank Birla Institute of Technology and Science, Pilani for providing the facilities rendered during the peer-review process.

Disclosure statement

No potential conflict of interest was reported by the authors.