Police and state troopers investigate the crash in which a teenage driver jumped off the elevated roadway to Third Avenue.

A 19-year-old man struck an MTA bus traveling toward Manhattan with his car on the Gowanus Expressway, then rear-ended another vehicle before he fled the car, ran several blocks and jumped more than 30 feet to Third Avenue in Sunset Park this morning, police officials said.

The driver, not yet identified, was rushed to Maimonides Medical Center with what police said was head trauma. He was reported in stable condition, police said.

The crash occurred at about 10 a.m. when the teen, who was driving a blue Honda, allegedly struck the bus, which was full of passengers. He then rear-ended another vehicle. Instead of staying on the scene, police say the youth fled the vehicle and began running eastbound on the highway. At about 49th Street, he jumped off the highway to the Third Avenue, suffering head and other injuries.

EMS personnel and police from the 72nd Precinct found him on the ground and took him to Maimonides Medical Center in Borough Park, where he was listed in stable condition. His name had not been released at press time.

Traffic on the Gowanus was jammed to the Belt Parkway after the crash, and passengers on the bus were apparently transferred to another bus to continue their trip.

It was unclear why the teenager fled the crash. Police say charges are pending.