Revealing mistake: When Jim hits the brakes in his stolen patrol car, the two pursuing police cars turn and flip over and over. As they roll, the 'roll cannon' is visible on the underside of one of the cars (a round steel tube in a hole in the floor) and at left, the two cannon slugs from both cars bounce down the road. This device fires the slug downward, and the force behind it lifts the car when the slug hits the road, launching the car over.