Vehicle running mode detecting system

A vehicle running mode detecting system comprising a relative speed calculating means which calculates the relative speed of a vehicle, equipped with the vehicle running mode detecting system, to a forward object on the basis of a time elapsed from a reference time based on which the time elapsed is measured and a change in the distance between the vehicle and the forward object during the time elapsed,

• a running mode determining means which determines whether the vehicle is running in a constant distance mode where the distance between the vehicle and the forward object is kept substantially constant or in a varying distance mode where the vehicle is accelerating or decelerating relative to the forward object and the distance between the vehicle and the forward object is varying on the basis of the change in the distance between the vehicle and the forward object, and
• a reference time updating means which receives an output of the running mode determining means and updates the reference time less frequently when the running mode determining means determines that the vehicle is running in the constant distance mode than when the running mode determining means determines that the vehicle is running in the varying distance mode.