Photo by Alexander Nguyen

A 29-year-old man was gravely injured Monday when the scooter he was riding collided with a trolley in Logan Heights.

The eastbound 2016 Vespa two-wheeler crashed into the back end of the westbound light-rail tram in the 3100 block of Commercial Street shortly after 3 p.m., according to the San Diego Police Department.

Paramedics took the rider to a hospital for treatment of life-threatening head injuries, SDPD Officer Robert Heims said.

Intoxication was not believed to have been a factor in the accident, according to police.

City News Service contributed to this article.