双向与单向道路网络：哪一个更高效？

摘要

To improve vehicular access and reduce driver confusion, city officials and urban planners have started a movement to convert downtown street networks from tra-ditional one-way operation to two-way operation. Two-way street networks increase economic activi-ty and livability, while one-way street networks increase vehicle flow. This paper points out that trip-servicing capacity is a better metric of network efficiency. Then the paper compares the trip-serving capacities of various one-way net-works and two-way networks with:left-turn lanes, left-turn pockets, and banned left turns. The results show that contrary to conventional wisdom and design handbooks, two-way networks are often more efficient than one-way networks. When trips are short, two-way net-works have higher trip-serving ca-pacities than one-way networks. Meanwhile, two-way networks with banned left turns impose less circuity than one-way networks.%　　为了改善机动车的可达性并避免驾驶人迷失，城市政府和规划师开始将中心城区传统的单向道路网络转换成双向行驶。双向道路网络可提升经济活力水平和中心城区的宜居性，而单向道路网络可提高通行能力。指出使用出行服务能力指标来衡量道路网络效率更适宜，将单向行驶与双向行驶道路网络的出行服务能力进行对比，后者交叉口的处理包括左转专用车道、左转渠化和禁止左转三种方式。结果显示，与传统认知和设计手册相反，双向道路网络通常比单向道路网络更有效率。在出行距离较短的情况下，允许转向的双向道路网络比单向道路网络的出行服务能力更高；禁止左转的双向道路网络比单向道路网络造成的绕行更少。