A motorcyclist was killed yesterday when he crashed into a tractor-trailer truck in Fawn, Allegheny County homicide detectives said.

The biker, David Simak, 53, of Arnold, was pronounced dead at the scene at 4:33 p.m. in the 200 block of Route 908, detectives said.

The medical examiner said Mr. Simak and the truck were approaching each other at 4:13 p.m. when the truck made a left turn just as the two vehicles were about to pass each other.

The trucker, Barbara Feather, 63, was not injured, police said.

The truck was being inspected this morning for adherence to safety regulations.