Traffic Stream Characteristics

Uninterrupted flow

Interrupted flow

Traffic Stream Parameters fall into two broad categories. Macroscopic parameters describe the traffic stream as a whole; microscopic parameters describe the behavior of individual  vehicles or pairs of vehicles within the traffic stream.

Volume and Rate of flow

Traffic volume is defined as the number of vehicles passing a point on a highway, or a given lane or direction of a highway, during a specified time interval. The unit of measurement for volume is simply “vehicles”, although it is often expressed as vehicles per unit time. Units of time used most often are per day or per hour.

Daily volumes are used to establish trends over time, and for general planning purpose. Detailed design or control decisions require knowledge of hourly volumes for the peak hour(s) of the day. Rates of flow are generally stated in units of vehicles per hour, but represent flows that exist for periods of time less than one hour.