Vehicle Code § 29006

(a) No person shall operate a vehicle towing another motor vehicle upon a freeway unless the towing vehicle is coupled to the towed vehicle by a rigid structure attached securely to both vehicles by nonrigid means.

(b) The requirements of subdivision (a) are not applicable to a vehicle towing a motor vehicle which has been disabled and is being towed from the point of disablement to the nearest and most accessible exit from the freeway.