v_r(t) - relative velocity

difference between the longitudinal velocities of the subject vehicle (SV) and the target vehicle (TV), vr(t), given by the equation; equivalently the rate of change with respect to time of the distance between the two vehicles
NOTE: A positive value of relative velocity indicates that the target vehicle is moving faster than the subject vehicle, and that the distance between them is increasing with time vr(t)= vTV(t)-vSV(t).

Application Area: Vehicle/roadway warning and control systems