A Study of the Minimum Safe Stopping Distance between Vehicles in Terms of Braking Systems, Weather and Pavement Conditions

Abstract

One of the most important factors in reducing traffic accidents is to keep safe distance between vehicles. The minimum safe distance depends on many factors such as the drivers' ability to react in accident, the vehicle braking system, the condition of the tires, the corresponding frictional forces provided by the tires, the speed of vehicles and many other factors. The main purpose of this study is to evaluate the above mentioned factors and obtain a relationship between speed and the so called minimum safe distance. In this study Gim&Nikravesh and Sakai models have been used in order to calculate the braking system force in each tire, using two-wheel equivalent model to calculate the braking force of vehicles and dynamic relations are used to calculate safe stopping time and distance between vehicles. Also the comparison of the minimum calculated safe distance with the relations delivered in Europe, Iran and British Codes are investigated. In this study, safety distance software has been introduced in order to calculate safe stopping distance based on different conditions. This software is designed and compiled by Delphi programming Environment and includes testing different hypothesizes for the back and front tires, calculating details of braking process such as stopping distance and stopping time, separating reflection distance and dynamic stopping distance, simulation of the stop process 3 seconds before confronting danger and finally drawing graphs related in the desired position. There is also a presentation of a recommendable formula in order to calculate the amount of safe distance for the two cases of ordinary braking system and ABS(Anti-lock Braking System) which covers the four situations of dry, wet, snowy, and icy positions.