Geometric Design Optimization of Speed Tables at Urban Arterials using UAV Assistance

Abstract

One of the primary risk factors at junctions on urban roads is vehicle speed. To curb over-speeding and road crashes at intersections, traffic calming measures are introduced. Current research aims at studying the impact of different geometries of recently constructed speed tables on the operational speed over such intersections. Since these treatments have been often used to regulate speed in other countries, an evaluation of their efficacy in the Indian context was required. This study utilises 6,000 vehicle samples of four different vehicle classes (two-wheeler, three-wheeler, cars, and buses) from 12 speed tables in total. The speed and acceleration kinematics in addition to the high-quality trajectory data over long road segments were extracted from the video recordings of an Unmanned Aerial Vehicle (UAV). Multi-factor Response Surface Methodology (RSM) was utilized to optimize the geometric parameters (variables) of the speed tables to achieve the requisite operational speed (predictor) at the considered measure. The box plots are provided to indicate descriptives of the parameters regarding the 85th percentile speed. Multiple linear regression and ANOVA identified the variables that were significant and fit to devise the required optimization model. This study can help in identifying the influence zone, concerning physical characteristics of speed tables and their effect on the design speed at the approaches of intersections at urban arterials. The outcomes of the study will cater to enhance the current guidelines and standards in India regarding speed table geometry for urban road sections.