Risk Assessment of Horizontal Curves Based on Lateral Acceleration Index: A Driving Simulator-Based Study
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ORIGINAL ARTICLE
Risk Assessment of Horizontal Curves Based on Lateral Acceleration Index: A Driving Simulator‑Based Study Tushar Choudhari1 · Avijit Maji1 Received: 13 December 2018 / Accepted: 2 October 2020 © Springer Nature Switzerland AG 2020
Abstract This study aims to evaluate the risk level associated with the geometric parameters of two-lane horizontal curves. It is measured using critical average lateral acceleration ( ac ), a new performance index derived from lateral acceleration profile data and representing a normalized lateral acceleration beyond a threshold value. The required data for the study were obtained from a fixed-base driving simulator in which 41 drivers drove through the geometric configurations comprising 26 horizontal curves. The hierarchical clustering analysis provided three risk clusters for ac values represented as low-, moderate-, and high-risk events. These risk clusters were analyzed for the geometric parameters, such as radius, design speed, gradient, and preceding tangent length. The cross-tabulation results indicated that the curve radius less than 100 m represented 2–10 times higher crash risk than the curves with a larger radius (> 100 m). The curves on the descending gradient exhibited two times higher risk than the one on the flat and ascending gradient. Further, the decision tree provided design speed and its interaction with gradient and preceding tangent length as the significant parameters to assess risk along curves. Overall, this study establishes the suitability of the newly developed performance parameter as a surrogate safety measure for evaluating the risk associated with different geometric configurations. Keywords Horizontal curves · Critical average lateral acceleration · Risk events · Hierarchical cluster analysis · Driving simulator
Introduction Highway safety depends on effective communication between the three primary factors: driver, vehicle, and road geometry. Improper communication between these factors leads to unsafe events or crashes. For example, an abrupt change in road alignment can surprise a driver and may lead to unsafe vehicle maneuvers. Such changes mostly observed in the curve sections of rural highways. A national report on road accidents in India showed that 50–60% accidents occur on rural highways [1]. Further, studies indicated that more than 50% of road fatalities take place in the curved sections [2]. Approximately 76% of curve-related crashes involve only a single vehicle, which comprises vehicle * Tushar Choudhari [email protected] Avijit Maji [email protected] 1
Department of Civil Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
runoff, overturning, or hit a fixed object [3]. Therefore, the horizontal curves of rural highways are considered as important and critical locations [4, 5]. Previous studies used the operating speed of vehicles as a performance parameter to identify risk associated with horizontal curves [5–8]. The operating speed exhibits a significant correlation with th
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