CRASH MAY HERALD RACING'S RISE.

Byline: Lisa Van Proyen Daily News Staff Writer

A 51-year-old man was recovering Monday from serious head injuries after a crash, possibly the result of a street race on Roscoe Boulevard, police said.

That incident and a fatal crash last week underscored the difficulty police said they have stopping street racers in the San Fernando Valley.

``The problem is you enforce, and then you push it into another area. It is kind of like chasing your tail, like a dog,'' said Los Angeles police Officer James Panek of the Traffic Safety Unit.

About 11:15 p.m. Sunday, 51-year-old William Briere was badly injured when his 1966 Ford Econoline crashed on Roscoe Boulevard near Lindley Avenue, said Detective R.S. Uber, the Los Angeles Police Department officer in charge of Valley Traffic detectives.

A witness reported seeing Briere racing his green van in a parking lane and hitting three parked vehicles, one of hit a fire hydrant, sending water onto the street, police said.

Briere, who was not wearing seat belts, overturned his van and was ejected.

Passers-by stopped and helped Briere, holding his head out of the water, Uber said.

On Friday, a 20-year-old West Hills man was killed after his car crashed in what police said was a street race with speeds up to 100 mph.

Paul Rolda was driving on Valley Circle Boulevard near El Canon Avenue when he lost control of his blue two-door 1991 Nissan 240 SX and hit a tree about 6:20 p.m. Friday, said LAPD Valley Traffic Detective Joseph Gomez.

Investigators said witnesses saw Rolda racing another car.

``There's every indication that he was racing,'' Gomez said. ``It could have been an impromptu reaction or a dispute - a challenge on the street.''

Police said they periodically see illegal racing on public streets and when the hot rodders are caught, they face arrest, seizure of their vehicle and the possibility of fines.