互通式立交主线同侧相邻入口最小间距研究

Study on Minimum Distance between Adjacent Entrances on Same Side of Mainline of Interchange

为提高高速公路互通式立交主线同侧相邻入口路段的交通安全,满足当前越来越复杂的互通式立交相邻入口的行驶安全需求,在规范的规定不够全面的情况下,以主线同侧相邻的匝道入口间距为研究对象,分析驾驶人进入上游入口后的驾驶特性。考虑车辆由匝道驶入主线时加速行驶距离、等待可插入间隙行驶距离和变换车道所需距离,建立了最小间距计算模型。结合相关调查结果及国外规范的成熟研究成果,对匝道入口处关键参数取值进行了分析,确定了不同匝道设计车速对应的合流鼻初速度、不同主线设计速度的合流点末速度、不同车型在加速段的平均加速度及合流车辆等待可插入间隙的平均等待时间等参数。通过对匝道合流处的驾驶员视距研究,分析了合流前识别决策距离、合流前换道距离以及合流前减速距离。最后从行车安全角度,提出了基于主线和上游匝道设计速度的高速公路主线同侧相邻入口最小间距指标建议值。结果表明:主线同侧相邻匝道入口最小间距与主线和匝道的设计速度均存在较强的关联,两者的速差越大,所需要的间距越大。《路线规范》中未区分相邻出口和入口,相邻出口的间距和相邻入口的间距相同,且未考虑匝道设计速度,所规定的主线同侧相邻匝道入口最小间距存在不合理的地方。

In order to improve the traffic safety of the adjacent entrance section on the same side of the mainline of expressway interchange and meet the current increasingly complex traffic safety requirements of adjacent entrances of interchanges, taking the distance between adjacent ramp entrances on the same side of the mainline as the research object in the case of insufficient regulations of the specification, the driving characteristics of driver after entering the upstream entrance are analyzed. Considering the accelerating distance, distance waiting for an insertable gap and the distance required for lane-changing when the vehicle enters the main line from the ramp, the a minimum distance calculation model is established. Based on the relevant survey result and the mature research result of foreign standards, the values of key parameters at the ramp entrance are analyzed, and the parameters such as the initial speeds of the merging nose corresponding to different ramp design speeds, the end speeds at the merging point for different mainline design speeds, the average acceleration of different vehicles in the acceleration section and the average waiting time of the merging vehicles waiting for insertable gap are determined. By studying the driver’s sight distance at the merging position of the ramp, the identification and decision distance, the lane-changing distance and the deceleration distance before merging are analyzed. Finally, the minimum distance between adjacent entrances on the same side of expressway based on the design speeds of mainline and upstream ramp is suggested from the perspective of traffic safety. The result shows that(1) The minimum distance between adjacent ramp entrances on the same side of the mainline is strongly related to the design speeds on mainline and ramp. The greater the speed difference between the two, the greater the required distance.(2) The Alignment Specification does not distinguish the adjacent exits and entrances. The distance between adjacent exits is the same as that between adjacent entrances, and the ramp design speed is not considered. The specified minimum distance between adjacent ramp entrances on the same side of the mainline is unreasonable.