加载中…2双环行车道时通行能力的理论模型
(2009-02-13 12:23:04)
1.
Highway Capacity of Double-loop Model
两条进口车道车辆进入交叉口时，左侧车流需与两条环行车流穿插，而右侧车流只需与外侧环行车流穿插。设 和 分别为左、右两侧进口车道能够进入交叉口的车辆数，则
Support people drive on the right. When the vehicles enter
the Traffic Circle from two incoming roads
seperatively, the traffic on the left will interpenetrate the
traffic flow in both of the loops, while the traffic on the right
only need interpentrate the outer-loop traffic flow. Let
式中: 的计算方法与式(3)相同，只是公式中的参数均表示外侧环行车流的参数。
In equality (4), the calculation method of
当左侧车辆进入交叉口时，可把环行车流假设成一当量车流，此当量车流与原车流具有如下对应关系:
When the vehicle on the left enter the traffic circle, we suppose the traffic flow in the traffic circle is an equivalent one, which possesses the following corresponding relations with the original traffic flow.
(1)当量车流车头时距大于 时，服从移位负指数分布;当量车头时距小于 时，服从均匀分布。
(1) When the headway of the equivalent traffic flow is more than , it follows shifted negative exponential distribution, but when it is less than , it follows even distribution.
（2)当量交通量等于两车道交通量之和，即: 。式中: 、 分别为内、外两侧环行车流的流量。
(2) When the equivalent traffic capacity equals the summation of the traffic flow of the two traffic lanes, i.e. . , represent the traffic flow of the inner loop and outer loop respectively.
(3)设当量车流车头时距小于 的概率时，则 。式中: 为两环行车流平均车头时距的均值，即 。
(3) let the headway of the equivalent traffic
flow is less than the possiblility of , then
.
(4) 。
基于以上假设，可推出当量车流车头时距具有如下的分布形式
Based on the above suppose, the headway of the equivalent traffic flow follows the following distribution pattern.
(5)
式中: 。
In equality (5),
参照式(3)的推导，可得出左侧车道的通行能力公式如下
According to equality (3), the traffic capacity of the left lane can be obtained as the following equality.
(6)
总的通行能力公式如下
The total traffic capacity is as the following equality.
1.3.2环形交叉口交织段通行能力分析
1.3.2 The analysis on the traffic capacity of the weaving section
环形交叉口交织段是车流争夺交通需求空间的场所，环道流量与进入交叉口的流量在此竞争，同时出交叉口车流与绕环车流竞争，形成车辆运行的紊乱区。在交织段内的关键运行特征是，进环车流要由入口道驶向环道1车道或2车道进行绕环，出环车流要由1车道驶向右转车道或先从2车道驶向1车道，从而与绕环车流产生冲突。入环车流与出环车流交替进出交织段，随着车辆的增加，不仅导致交织段车辆密度增加，行车速度降低，也必然会引起车头时距重新分布。
Usually, the traffic aggressively entering a roadway or changing lanes in the weaving section, where always causes a traffic chaos. The characteristics function of the weaving section is that the incoming traffic flow must circle in the inner circle or the outer one, while the outcoming traffic flow must change lane from the inner lane to the outer one, or from the outer lane to the right turn lane. Therefore, it causes a collision with the circling traffic. When the incoming traffic and outcoming traffic enter the weaving seciton alternatively, with the increase of the traffic, it leads to the traffic density increases, the traffic velocity decreases. Therefore, the headway of the equivalent traffic flow will redistribute.
然而，交织段内交通流无论如何分布，其必须遵循如下约束条件:
a)车辆转换车道时，目标车道有足够的安全车头时距;
b)每一车道的交通量不能超过该车道作为同等道路条件下基木路段的通行能力(BFC);
However, whatever the redistribution of the headway in the weaving section, it follows the following restrictions: a) When a vehicle change its lane, there must be sufficient headway on the target lane; b) The traffic flow on each lane can not be more than the capacity of the basic traffic capacity (BFC) on the same road; c) the total incoming flow can not be more than the maximun incoming flow capacity, . The restrictions are showed in the figure 2.
0车道没有变换车道(右转)的交通量、0车道汇入1车道的交通量。
In figure 2, the 、 、 、 、
入口车道= incoming road
0车道（右转车道） = 0 lane（right turn lane）
交织段 = weaving section
出口车道= outer road
环道2车道 = the inner lane in the traffic circle
环道1车道 = the outer lane in the traffic circle
Therefore, the highway capacity of the weaving section as a constraint condition can not be more than the capacity of the basic traffic capacity (BFC) on the same road. So, it can be represented as the following:
As the incoming traffic flow of the weaving section is less than the standard traffic capacity of the road, and the incoming traffic flow is less than the maximum incoming traffci flow, , in equality 3.1. Therefore, we can get:
由于环形交叉口交织段的通行能力为单位时间内入口道、环道与右转的最大交通量之和，从而环形交叉口交织段通行能力为:
As the traffic capacity of the weaving section is summation of the traffic flow from, in and out of the traffic circle within a unit time, then the traffic capacity of the weaving section is:
Therefore, the traffic capacity of the weaving section has the following Linear Programming Model:
这样.基于间隙接受理论和线性规划技术.建立出了环形交叉口交织段的通行能力模型。
In this way, according to gap acceptance theory and Linear Programming Model, we can establish a model of the weaving section in a traffic circle.
附：
环形交叉 rotary intersection
引道 approach road
分道转弯式交叉口 channelized intersection
外侧车道 nearside lane
内侧车道 fast lane
穿插 interpenetrate
冲突 collision
冲突点 collision point
内环车道
外环车道 outer lane
交织段 weaving section
当量车流车头时距 the headway of the equivalent traffic flow
车头时距 headway
进环车流 incoming traffic
通行优先权 access priority
锯齿形公交优先进口道 Indented bus priority approach
二次控制信号灯 Primary-Secondary traffic light controls
信号控制的周期时间 cycle time of the traffic light control
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