A collision-prediction unit for a vehicle including a road condition
detector, a maximum deceleration estimator, a forward vehicle detector, a
forward vehicle deceleration calculator, and a collision examiner is
provided. The road surface detector detects a condition of a road surface
on which the vehicle travels. The maximum deceleration estimator
calculates a maximum vehicle deceleration for the vehicle on the road
surface having the detected condition. The forward vehicle detector
detects a moving condition of a forward vehicle located ahead of the
vehicle. The forward vehicle deceleration calculator calculates a forward
vehicle deceleration based on the moving condition of the forward
vehicle. The collision examiner determines whether a collision between
the vehicle and the forward vehicle is imminent by comparing the forward
vehicle deceleration to the maximum vehicle deceleration of the vehicle.