Traffic Impact Analysis of Acceleration Lane Length Considering Dedicated Lane Location for Connected and Autonomous Vehicles: A Virtual Segment Study of Chinese Expressways

In the initial stages of Connected and Autonomous Vehicles (CAVs) development, the deployment of dedicated lanes for autonomous driving is an important measure to improve traffic efficiency and safety. To study the impact of considering acceleration lane length on the design of highway merging areas in mixed traffic flow environments, as well as its correlation with road safety and traffic efficiency, two design schemes for acceleration lane length in highway merging areas with different positions of dedicated lanes were investigated: setting the dedicated lane on the innermost or outermost part of the main highway. By designing different road traffic volumes and market penetration rates of CAVs, SUMO simulation was used to analyze the impact of acceleration lane length in highway merging areas on road traffic from both a traffic efficiency and safety perspective under different CAV penetration rate conditions. The results show that although increasing acceleration lane length can improve average vehicle speed and reduce delay, its effect is not very significant. When the dedicated lane is set on the innermost part of the mainline, both average vehicle delay and speed performance are better than when it is designed on the outermost part. Increasing lane length leads to an upward trend in average speed but with limited growth rates—maximum growth ranges from 0.28% to 2% during off-peak periods and from 0.52% to 1.52% during peak periods. At the same time, increasing lane length reduces average delay by a range between 0.39 s to 1.74 s. Additionally, vehicle conflict occurrences decrease with increasing lane length during off-peak periods but show no significant change during peak periods.