1. An antioverride mechanism for a speed control unit that is responsive to the road speed of a vehicle having a throttle pedal linkage and a carburetor with a throttle arm comprising; (a) a cable having a flexible sheath and a flexible core within said sheath and freely slidable relative thereto, said sheath having one end adapted to be secured to said speed control unit, said core having one end adapted to be secured to the speed control unit and movable thereby relative to said sheath; (b) a tubular housing having a first end secured to the other end of said sheath and being adapted to receive said core; (c) a slidable member positioned within said tubular housing for sliding movement relative thereto, the other end of said core being secured to said slidable member; (d) resilient means for resiliently biasing said slidable member away from said first end of said tubular housing, the resilient force imposed by said resilient means being insufficient to restrain movement of said core by said speed control unit relative to said sheath; (e) ball stud means for pivotally securing said slidable member to said throttle arm; and (f) linkage means for securing said housing to said throttle pedal linkage whereby said housing will move in response to movement of said throttle pedal linkage.