A vehicle speed control system includes a first electronic control unit for transmitting
a difference between actual and target vehicle speeds and control constants that
vary depending on the vehicle speed difference when it determines fulfillment of
vehicle speed control conditions, and a second electronic control unit for performing
the vehicle speed control based on the vehicle speed difference and control constants
received through a communication line. Change of the control constants for adjustment
of a vehicle speed control function of the system can be easily carried out by
changing the control constants stored in the first electronic control unit.
