Abstract: The transition section of parallel acceleration lane plays a critical role in ensuring the operational efficiency and safety of freeway merging areas. Existing models for calculating the length of transition sections yield significant differences in results due to varying considerations. Based on this, a comparative study on multiple calculation models for transition section length of parallel acceleration lane was conducted. According to the measured data and the literature at home and abroad, theoretical calculation results of different models were given. Taking the average operating speed of merging vehicles and the number of traffic conflicts of mainline vehicles as indicators, VISSIM simulation was employed to analyze the rationality of transition section length corresponding to each model. The research results indicate that the vehicle average speed corresponding to the transition rate model is the highest, the traffic conflict number of the lateral lane-changing model is the least, and the lane-changing driving distance model performs optimally in terms of both average speed and traffic conflict number. Finally, it is recommended that when the design speed of the mainline is 120 km/h, 100 km/h and 80 km/h, the lengths of the transition sections of parallel acceleration lanes are respectively set at 150 m, 130 m and 115 m.

Key words: highway engineering; freeway merging area; parallel acceleration lane; transition section length; VISSIM simulation

摘要： 平行式加速车道渐变段对保障高速公路合流区运行效率与安全具有关键作用，现有渐变段长度计算模型因考虑因素不同，导致结果差异显著。基于此，对比研究了多种平行式加速车道渐变段长度计算模型。基于实测数据与国内外文献，给出了不同模型理论计算结果；并以合流车辆平均运行速度及与主线车辆交通冲突数为指标，运用VISSIM仿真分析各模型所对应渐变段长度的合理性。研究结果表明：渐变率模型对应的车辆平均速度最高，横移换道模型的交通冲突数最少，换道行驶距离模型在平均速度与交通冲突数方面均表现最优；最终建议，在主线设计速度为120、 100、 80 km/h时，平行式加速车道渐变段长度分别取150、 130、 115 m。

关键词: 道路工程；高速公路合流区；平行式加速车道；渐变段长度；VISSIM仿真