The victim, Shamel Stroman, 33, of East Windsor was spotted on the shoulder of South Main Street around 7:30 p.m. Tuesday, and was apparently the victim of a hit-and-run.
Police said an unknown motorist struck the victim while driving northbound on Main Street, also known as U.S. Route 5, and fled the scene.
Route 5 was closed between Tromley Road and Phelps Road until just before 10:30 p.m.
Police do not have a description of the suspect's vehicle.
A witness came forward after the crash and said he was at a red light while driving north on Rt. 5 when he saw a man run into the road and jump onto the back of a large silver box truck that was stopped directly in front of him at the light. The man couldn't hold on after the truck started accelerating when the light turned green. Then man fell back, but immediately got up and seemed uninjured.
The witness' description of the man matched that of the man who jumped on the truck.
The witness drove off and didn't see how the person get hurt, and police are still unsure of what transpired exactly, though Stroman did say he was hit by a vehicle.
Police say Stroman's condition has improved since Tuesday night.