Research on the Reasonable Length of the Median Opening for Five-Lane Traffic Flow During the Reconstruction and Expansion of Expressways

This article refers to relevant specifications and standards, taking the median openings of the five-lane as the research object. It designs combined schemes with design speeds of 60 and 80 km/h for two transition scenarios: transition from double sided two-way traffic to single sided two-way traffic, and transition from left single sided two-way traffic to right single sided two-way traffic. Based on vehicle dynamics stability simulations, safety evaluations are conducted for each scheme. The results indicate that if the proportion of small vehicles in the transition section is high, considering engineering economy, it is advisable to adopt an opening length of 149 m, which can meet the requirements for vehicle driving stability; if the proportion of large vehicles in the transition section is high, it is advisable to adopt a large-radius circular curve design alignment scheme to improve road safety.