A vehicle headway maintenance assist system is provided that provides a haptic notification to an accelerator to alert the driver under prescribed conditions. The system changes a drive force/accelerator actuation relationship between an accelerator actuation amount and a target drive force or torque under the prescribed conditions. In particular, system changes a first drive force/accelerator actuation relationship to a second drive force/accelerator actuation relationship based on a vehicle running condition that was detected so that the driver more readily notices the haptic notification (e.g., an accelerator actuation reaction force) when the haptic notification is being applied to the accelerator to alert the driver under the prescribed conditions.