Microscopic fundamental relationships between vehicle speed and spacing in view of asymmetric traffic theory

Vehicle´s cruising speed and spacing have been assumed to have symmetric relationship in acceleration and deceleration for long times. However, more evidences have been observed from 1960s to recent days. Recently obtained NGSIM database provides very detailed level of trajectories data, which enable us to reveal the details of the driver´s behavior. Based on the understanding by observing NGSIM data, we derived and proposed fundamental relationships between vehicle´s cruising speed and spacing from asymmetric traffic theory´s view. This relationship includes A-curve and D-curve in diverse traffic conditions, which can be used as boundaries of equilibrium regions. The suggested model provides background in developing asymmetric car-following models with reasonable number of parameters, and can be applied in many areas including microscopic simulation.