CHP CLOSES BOOK ON ONE OILY CASE.

Byline: Orith Goldberg Staff Writer

It was a slick operation.

An undercover California Highway Patrol officer has solved the mystery of the slippery substance that appeared regularly before dawn on the westbound transition of the Ronald Reagan Freeway to the southbound Golden State Freeway.

It was a bus leaking oil, investigators said Thursday.

``They think it's the incline, centrifugal force on the curb and possible mechanical problems,'' said CHP Officer Wendy Moore.

What is unclear still, however, is the source of a slippery substance that regularly appears on the San Diego Freeway transition to the 118. That investigation continues.

One thing is sure: These slippery liquids have been blamed for at least two crashes and more than 15 reports by motorists in the past few weeks.

It turns out that on the 118 transition road the culprit was a Coach USA bus, or so it was revealed on videotape from a camera mounted on a CHP cruiser.

As the bus negotiated the transition, it appeared to leave a trail of what turned out to be oil, Officer Moore said.

Officials surmised the oil leak could have been caused when the engine developed pressure as it traveled on the incline, said Moore.

The bus contracted by the Metropolitan Transportation Authority operates on the 167 line.

Greg Bush, a Coach USA project manager, said CHP officials inspected the suspected bus and authorized it to return to the road once it is repaired and cleaned.

`We would never put a bus out on the road if we saw a leak,'' Bush said.

CHP's Moore said after specialists inspect the bus, a report would be compiled and submitted to the District Attorney's Office for review.