Characterization of road traffic flow from measured data of speed and time-headway -relationship between density ( k ), flow rate ( q ) and speed (V )-

Basing upon the newly defined parameters of vehicle density on road (k ) and flow rate (q), the traffic flow was analyzed from video images taken at urban, suburban and expressway. The measured data are time-headway (T) and speed (V). Both T and V are measured using the unit of second (s) and meter par second (m/s), respectively. The data were collected manually by using stopwatch. The parameter k was defined from T and V , then it became a non-dimensional parameter as a normalized one that was confined between 0 and 1 (0 < k < 1). The data of about 1000 vehicles were obtained. The relationship between k and V (k -V characteristics) was examined, which obeys the exponential function with good accuracy.