Discussion Topics Why do we call the traffic system？ What are characteristics of the traffic system? What is the future direction of development of the traffic system？
Today Topic: Traffic Stream Characteristics Traffic Stream Parameters Volume and Rate of Flow Volume, Demand, and Capacity Volume Patterns and Characteristics
Traffic Stream Parameters V2 V1 Density – Spacing Average speed – Individual speed Flow rate – Headway Macroscopic Microscopic
How to measure traffic flow? 1 min Distance 100 m Headway Observer Spacing Individual speed Instance Time
Volume Volume: the number of vehicles passing a point on a highway, or a given lane or direction of a highway, during a specified time interval 交通量：在选定的时间段内，通过道路某一地点或 某一断面的交通体的数量 Unit of measurement: vehicles per day or per hour, veh/h or vph, veh/d, peds/h or peds/d
Flow Rate Flow rate: generally stated in units of “vehicles per hour”, but represent flows that exist for periods of time less than one hour 流率：短于一个小时的交通量转换成的小时交通量
Volume, Demand, and Capacity
Flow Characteristics Temporal flow patterns Monthly flow patterns Daily flow patterns Hourly flow patterns Spatial flow patterns Linear flow patterns Network flow patterns Directional flow patterns Flow patterns in intersections Lane use flow patterns Modal flow patterns Flow patterns in multimodal transportation facilities Passenger Car Equivalents (PCU)
Monthly Flow Patterns AADT – 年平均日交通量 MADT – 月平均日交通量
Daily Flow Patterns ADTi – 星期 i 的年平均日交通量
Hourly Flow Patterns 高峰小时交通量（PHV） 流率（ Flow Rate） 高峰小时系数（Peak Hour Factor, PHF） – 高峰小时交通量与高峰小时流率之比
Directional Flow Patterns 方向分布系数 – 重车方向交通量所占比重
Flow Patterns in Intersections
Lane Use Flow Patterns
(Passenger Car Equivalents) 车辆换算系数 (Passenger Car Equivalents) 车辆类型 小客车 大型客车 大型货车 铰接车 设计长度 6 12 18 设计宽度 1.8 2.5 换算系数 1.0 2.0 3.0 引自CJJ37-2012《城市道路工程设计规范》