iv saw the kits tim124 posted up, just thaught renault did one thats all, looks like its one of them kits then, theres load of ways of doing it, some have a pneumatic ram attached to where the accelerator cable meets the engine, they read the road speed from the ECU i think, for cars without and ECU iv seen a magnetic colar thats fits around the drive shaft and goes off engine revs. In the cockpit a mini computer module reads all the info and decides to increase or decrease the throttle to keep the same roadspeed, unfortunatly it doesnt break...thats up to u. I think that would do my mate though its just so he can keep his foot off the accelerator, after 2 7 hour drives a week end his foot gets cramp haha