Rostra's speed-limiting systems work by blocking communication from the accelerator pedal being controlled by the driver's foot once the set speed limit has been reached. If the vehicle is equipped with an original equipment cruise control system, the steering wheel or control stalk-mounted cruise control buttons can allow a driver to surpass the set speed limit. For this reason, installers MUST also order part number 250-3766 which will disallow cruise control functionality past the set speed limit.