The vehicle was driving on cruise control at 55 mph approaching an intersection with a stop sign. Attempted to brake to cancel the cruise control, but vehicle sped and continued gathering speed so that the driver lost any control over the speed. Frantic application of the brake did not have any effect on the speed. The vehicle shot across a south bound highway, collided with traffic signs in the center, crossed northbound lanes, jumped a four foot berm and landed in bushes where the air bags deployed.