Dependency of Vehicular Operating Speed on Road Geometric Characteristics: A Review

Abstract

Operating speed plays a vital role in geometric design. It varies with location and different physical road characteristics. This paper outlines the description of the importance of geometric design consistency, data collection, estimation of consistency indexes, model section and proposes a methodology for road safety evaluation in terms of operating speed clubbed with road geometric characteristics. The objective of this paper is to understand how various factors on the roads affect operating speed of vehicle classes. The review considers the effect of road geometric characteristics on operating speed of various classes of vehicles for state highway (SH) and national highway (NH) at curve points. This includes the understanding about the development of operating speed models for horizontal curves and preceding and succeeding tangents, as well as the study of the characteristics and relationships between acceleration and deceleration rates before and after horizontal curves. Various authors have collected spot speed data for cars, heavy commercial vehicles (HCV), heavy passenger vehicle (HPV), motor two-wheeler (MTW) using spot speed camera, radar gun, LiDAR gun, speed gun, laser gun, global positioning system (GPS) device, video camera, etc. The various geometric indices of a rural highway are determined using Civil 3D and Google Earth Pro. Lateral friction coefficient at the curve is determined using Skid Resistance Tester. Studies on operating speed prediction models are limited in developing countries like India, specifically for SH and MDR. This literature also discusses different kinds of models developed to justify the relation between operating speed and other latent independent variables. The paper also discusses methodologies adopted in understanding important variables and extracting most significant ones by various authors from different categories. From the rigorous literature survey, the most important and most correlated latent variables are suggested for inclusion in further studies related to operating speed on SH and NH particularly at the curve regions of the highways. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.