Police are investigating after a road rage incident escalated into an assault in Madison. Madison police say a man was involved in a road rage incident on the Beltline around 6 P-M Saturday. Officers say he followed the other vehicle involved into the parking lot of a business. Investigators say that’s when the other driver got out of his vehicle, and allegedly beat up the man who followed him, knocking him unconscious. Officers say the victim described the car as black, possibly a Chevrolet Impala, with Illinois plates. Police searched the area but could not find a car matching that description. The case remains under investigation.