考虑主线车道数与匝道车速的快速路出入口最小间距计算方法

A Calculation Method for Minimum Spacing Between Entrances and Exits on Expressways Considering Number of Lanes on Mainline and Ramp Speed

为完善现行标准、规范,满足日趋精细化的工程实践需求,开展了快速路出入口最小间距计算方法研究。总结了快速路出入口组合形式与最小间距划分方式,根据车辆变道目的,提出将交织段进一步划分为合流变道段与分流变道段;以尽量避免分合流车辆对主线交通流干扰为原则,重新建立了不同组合形式下出入口最小间距计算式。针对快速路主线自由流、稳定流上段和稳定流3种运行状态,考虑匝道车速,分别建立了加、减速段长度计算模型;引入间隙接受理论,建立了等待合流段长度计算模型;以变道条件最差为前提,结合主线车道数,提出了车道变换长度的确定方法,并据此优化了加速车道、减速车道、车道变换、出口标志识认4类长度的计算方法。给出了三级服务水平下,对应于不同主线设计速度、车道数和匝道设计速度的出入口最小间距推荐值,结果表明,在76.5%的工况中,推荐值小于规范值;推荐值高于规范值的情况集中于主线设计速度高于80 km/h,单向车道数为4的工况中;对应于60 km/h,80 km/h,100 km/h的主线设计速度,推荐值平均比规范值低160 m,138 m,70 m。与规范值相比,推荐值能满足更为灵活的设计需求。

In order to improve current standards and regulations,as well as to meet the requirements of increasingly refined engineering practice,a calculation method for minimum spacing between entrances and exits on expressways is studied.The combinations of entrances and exits on expressways and division modes for minimum spacing are concluded.According to lane-change purpose of vehicles,it is proposed to further divide weaving segments into merging segments and diverging segments.In order to avoid interferences of diverging or merging vehicles on main line traffic flows,calculation formulas for the minimum spacing between entrances and exits in different combinations are re-established.Considering 3 kinds of traffic conditions on the mainline,which are free flows,upper stable flows,and stable flows,a calculation models for length of acceleration and deceleration segments are separately established taking account of ramp speed.Gap acceptance theory is applied to a model for calculating length of merging-waiting segments.Based on the worst lane-change condition,a method for determining length of lane change is proposed considering the number of lanes on mainline.Then calculation methods to optimize 4 kinds of lengths,i.e.acceleration lane,deceleration lane,lane change,and exit sign recognition,are developed.Minimum spacing between entrances and exits corresponding to different design speeds of mainline,numbers of lanes on mainline,and design speeds of ramp under the third level of service are recommended.The results show that in 76.5%traffic conditions,the recommended value is lower than the standard one.The recommended value is higher when the design speed of mainline is higher than 80 km/h and the number of one-way lanes is 4.The average recommended values are 160 m,138 m,and 70 m lower than the standard ones when the design speed of mainline are 60 km/h,80 km/h,and 100 km/h,respectively.Compared with the standard values,the recommended values can meet more flexible design requirements.