Why did the 21-year-old cross the road?

Benjamin Carpenter, 21, was crossing a Michigan highway in his wheelchair when he became stuck in a semitrailer's grille and pushed for miles before the unknowing driver was pulled over, police said on Thursday.

Carpenter escaped unharmed, saying, "It was quite a ride," police said.

Click here to listen to the 911 tape.

Carpenter was attempting to cross on Wednesday when the light turned green and his wheelchair became hooked onto the front grille of the truck, which reached 50 mph during the 4-mile trip down Red Arrow Highway, Michigan State Police Trooper Michael Sinke said witnesses reported.

Carpenter was taken to a hospital as a precaution. He had been secured to his wheelchair by a seat belt.

Witnesses reported that the light turned green, so the truck took off, never seeing the wheelchair in front of him or the fact that it had attached to his front grill. When officers stopped the truck at a private business, Carpenter was in a calm state.

"The man spilled his soda pop, but he wasn't upset," said Sgt. Kathy Morton of the Michigan State Police.

Sinke said when he arrived at the scene, the man told him "'Yeah, I'm fine. I just went for a little ride.'"

"He was surprisingly normal," Sinke said.

About 4 p.m. Wednesday, a caller told police dispatchers, "You are not going to believe this: There is a semi truck pushing a guy in a wheelchair on Red Arrow Highway," state police said in a release.

Authorities initially wondered whether the report was a prank call until others called with similar reports.

When the truck finally was stopped, the driver didn't believe officers until he stepped from his cab and saw for himself.

"When he saw us, he was like, 'What's going on?"' Morton said.

"The truck driver had no idea," Sinke said. "[He] was in a state of shock."

Paw Paw Police Department Office Manager Susan Millek said their department got the initial call around 3:30 p.m. and Sgt. Kirk Goodrich and officer Tim McMeekan responded to the call. McMeekan said the incident was labeled a car pedestrian accident and he was prepared for a scene much worse than what he found.

"We were obviously relieved and shocked to see what happened," McMeekan said.

He said the family was notified within a few minutes and because the man is an adult, the department called to have someone pick him up.

Officers who responded to the scene said the fact that the man was unharmed made this story that much more unbelievable.

"Just the way he was uninjured. It’s just unbelievable," Sinke said. "Obviously someone was looking over him yesterday. I could go another hundred years in law enforcement and never see that again."

The Associated Press contributed to this report.