We were returning from a trip towing our TT. We were in the slow lane, which was closed up ahead because of an accident. Turned on my signal to move over, saw an opening and accelerated. When the idiot in front of me in the middle lane came abreast of the accident, he slammed on his brakes coming to a complete stop to look at the accident. I hit my brakes but there was no way I was going to stop. Fortunately, the fast lane was empty and I didn't lose control making an emergency maneuver towing a trailer.