A motorcyclist was clinging to life today after he was pinned under a bus in a chain-reaction Lincoln Tunnel crash that caused morning commuter chaos.

He was rushed to Bellevue Hospital after the 7:26 a.m. crash, which also injured 52 people on buses headed to Manhattan from New Jersey.

VIDEO: 3 BUSES, MOTORCYCLE CRASH INSIDE LINCOLN TUNNEL

Fourteen people in all were seriously injured, the Port Authority said.

Surveillance video from the tunnel shows the unidentified motorcyclist was weaving between lanes when the crash occurred, said sources.

When a NJ Transit bus right behind the motorcyclist stopped for traffic, a second NJ Transit bus hit it from behind — pushing the first bus into the motorcyclist, witnesses said.

The motorcyclist ended up pinned under the first bus, witnesses said.

James Riley of Old Bridge, NJ, who was on the second bus, explained: “We hit the bus in front of us and we pushed it forward.

The motorcyclist “was completely underneath bus one. The only thing that wasn’t was his head, and he had his helmet on,” said witness Alyna Silva, 20, one of only two passengers aboard a third bus, which she said just avoided being involved in the crash.

Inside the buses “was chaos,” said Nick Stahl, 35, also of Old Bridge, who was traveling to Manhattan with his girlfriend.

“Blood was everywhere. Everyone was screaming for help,” said Stahl, who had multiple fractures in his face. “We’re just happy to be alive.”

The accident happened in the tunnel’s center tube, about a quarter-mile from the Manhattan side. It took 3½ hours for rescuers to get all the injured out of the tunnel.

While she was being treated at Bellevue Hospital, 33-year-old Perri Grinberg of Marlborough, NJ said she was “Looking around at people that were hurt worse than you and realizing, ‘God, I was so lucky.’”

Traffic wasn’t back to normal until early afternoon, the Port Authority said. The crash remains under investigation.