Traffic characteristics. In the event that we need to think about the Traffic attributes and their expectations, it is appropriate to furnish at any rate their short posting with definitions and shared relations. The three fundamental characteristics in traffic flow theory are flow, speed, and density. Traffic flow. Traffic flow can be additionally found in some literature named as flow, flow rate or volume. Nevertheless, all these terms can be used interchangeably. It is characterized as various vehicles passing a point in a given timeframe. It is typically communicated in units of vehicles per hour vph. Other conceivable units are for example vehicles per hour, per lane, vphpl, passenger car units per hour pcu/hr, or passenger car units per hour per lane pcphpl or in easier readable form pc/h. ln The equation for counting traffic flow is simple where q is traffic flow vph n is number of vehicles passing a spot on the road in a given interval t. The special value of traffic flow is capacity c which defines the maximum hourly rate under prevailing roadway conditions. Since it is convenient to measure traffic flow in 15-minute intervals a quantity called peak hour factor PHF is presented. Hence is obvious that PHF can theoretically be in the interval 0 25 PHF 1 0. Peak hour factor can be understood as an indicator of flow fluctuations within the hour Introduction.