公路运输系统
Speed, v
v A Bk A 0, B 0 A
AB
Density, k
A2 4B
Flow, q
A
AB
2B
Density, k
Speed, v
A
A
A2
2
4B
Flow, q
公路运输系统
➢ 交通流基本理论
Example 3 Given that the relationship between speed and
For example, 200 vehicles observed in a 10-minute period implies a flow rate of 1200 veh/hr.
公路运输系统
➢ 交通流基本理论
1. 交通流常用变量
•Spacing (s) in meters is the distance between successive vehicles in a traffic stream as measured from the front bumper to front bumper. •Headway (h) in seconds is the corresponding time between successive vehicles as they pass a point on a roadway.
distance
time
公路运输系统
➢ 交通流基本理论
Example 2
公路运输系统
➢ 交通流基本理论
2. 速度-密度-流量关系
•Relationships of q-k-v were tested in terms of goodness of fit to actual field data •Relationships were supposed to satisfy these boundary conditions: a. zero flow at zero density b. zero flow at max density c. free-flow speed at zero density d. convex flow-density curve (i.e., there is a maximum flow)