Assessment of speed variability on the horizontal curves using vehicle trajectories for geometric design consistency and safety evaluation of a two-lane rural highway passing through mountainous terrain

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Horizontal curves play a crucial role in providing a smooth and safe transition from one tangent to the successive tangent. But, the crash data corresponding to Indian highways shows that the crashes on curves went up by 46.05% on average between 2016 to 2021. In this scenario, evaluating the consistency of horizontal curves is important to improve safety. There are various consistency measures that are classified based on parameters such as operating speed, driver workload, alignment indices, side friction, and driving dynamics for assessing geometric design consistency. Among these measures, Lamm’s criteria developed based on operating speed, is widely accepted across the world and used for consistency evaluation. However, in evaluating the consistency using the Lamm’s criteria, past studies estimated operating speed (V85) using spot speed data collected at the center of the curve. Recent studies with driving simulators and GPS instrumented vehicles found that speed is varying on the curve, and collected minimum operating speed on the curve for modeling operating speed reduction models. Majority of the operating speed reduction models that were developed are meant for rural highways in plain terrain and these models are not applicable to the highways passing through mountainous terrain. Besides, none of the studies have attempted to study the design and operating speed consistency for the horizontal curves of two-lane highways passing through mountainous terrain.
Supervisors: Mallikarjuna C and Venkatesh, T