Vehicle speed control system using lockup clutch for automotive vehicle

A vehicle speed control system for a vehicle equipped with an automatic transmission (70) with a torque converter detects whether the automatic transmission is put in a lock-up condition and corrects a command drive torque (dFC) according to the lock-up condition. Particularly, the control system decreases a correction quantity of the command drive torque (dFC) when the automatic transmission (70) is put in the un-lockup condition. Therefore, the control system can adapt its response characteristic to a controlled system response characteristic which varies according to the lock-up condition of the transmission.