Dynamic Illumination Method for Rural Highway Intersections with Traffic Flow Changes

Abstract

The conflicts between vehicles and vulnerable road users are frequent at rural highway intersections. Improving lighting conditions at intersections can significantly reduce the likelihood of nighttime accidents. This study aims to develop a dynamic illumination method for rural highway intersections with traffic flow changes. First, the safety design principles of a lighting scheme were formulated for minimum illuminance, vehicle speed, and traffic risk at intersections. In addition, a traffic risk quantification model for intersections was developed with illuminance and traffic flow parameters as inputs, incorporating gap acceptance theory and the braking safety distance model. Second, combining safety design principles and a traffic risk quantification model, a calculation method for optimal illuminance at intersections was designed with minimum illuminance as the optimization objective, and considering the risk at intersections not exceeding the safety threshold as the constraint. Finally, a case study was conducted in a simulated environment. Evaluation results demonstrate that limiting the maximum nighttime vehicle speed at intersections to 50 km/h can maximize the energy-saving rate of the lighting system while ensuring traffic safety and transport efficiency. The advantage of the method is that it can calculate the safe lighting scheme for highway intersections without any historic accident data and save lighting energy consumption. It increases the feasibility of promoting lighting facilities at rural highway intersections.