Abstract: To study the influence of the additional channelization island type exit on expressway traffic flow, this paper establishes a cellular automata model for it. Based on the KKW (Kerner-Klenov-Wolf) model, three lane-changing rules are introduced and set by sections to describe the lane-changing behavior of vehicles under the influence of the additional channelization island type exit. According to the geometric characteristics of the direct connection between the main and side roads, the process of vehicles on the main road passing through the exit is equivalently simplified, and the rules of vehicles driving out are defined under the additional channelization island type exit. The numerical simulation results show that the channelization island can make the inside lane of the downstream side road play the role of the auxiliary lane by guiding vehicles from the upstream of the channelization island to merge with the outside lane. Under its setting, the direct interference caused by side road traffic flow on vehicles driving out is relieved, and the traffic efficiency of the main road is significantly improved. However, the mandatory lane changing of side road vehicles after passing through the channelization island will cause disturbance to the stable outgoing traffic flow and induce local congestions, which will affect the further evacuation of outgoing traffic flow and lead to the decrease of saturated flow and average speed of the main road. In addition, the channelization island causes the road reduction bottleneck to form on the side road, and the total saturated flow of the side road decreases significantly under its influence. The occupation of the channelization island on the inner lane of the side road makes its flow rate and average speed lower than those of the outer lane, and the traffic efficiency is more affected.

Key words: traffic engineering, cellular automata, microscopic simulation, urban expressway, traffic flow, traffic organization

摘要： 为研究附加导流岛型出口对快速路交通流的影响，本文建立针对附加导流岛型出口的元胞自动机模型。基于KKW (Kerner Klenov Wolf)模型，引入3种换道规则并分段设定，以描述附加导流岛型出口影响下的车辆换道行为。针对主辅路直接衔接的几何特点，对主路车辆经由出口驶出的过程等效简化，定义附加导流岛型出口下的车辆驶出规则。模型的数值仿真结果表明：导流岛通过引导辅路车辆在导流岛上游向外侧车道合流，能够使辅路下游的内侧车道起到辅助车道的作用。在此设置下，辅路车流对车辆驶出造成的直接干扰得到缓解，主路的通行效率显著提高。然而，辅路车辆经过导流岛后的强制换道会对驶出的平稳交通流造成扰动而诱发局部拥堵， 影响驶出车流的进一步疏散，导致主路饱和流量和平均速度的下降。此外，导流岛使得辅路形成道路缩减瓶颈，在其影响下，辅路总饱和流量大幅下降。导流岛对辅路内侧车道的占用使得其流量和平均速度均低于外侧车道，通行效率受到更大的影响。

关键词: 交通工程, 元胞自动机, 微观仿真, 城市快速路, 交通流, 交通组织