Los Angeles County and Southern Pacific Transportation Co. officials on Friday announced agreement on a landmark purchase of 177 miles of valuable rights of way expected to speed development of a regional commuter rail system with a critical link to Orange County.

The $450-million deal, reached for 40% less than the railroad was seeking, contains a five-mile stretch of the old Pacific Electric trolley line between Beach Boulevard in Stanton and the Los Angeles County line that Orange County transportation officials said could open the door to commuter rail traffic between Santa Ana and Los Angeles within five years.

Traveled by hordes of tourists and business people in its heyday, the Pacific Electric line is now mostly a weed-strewn dirt strip through one of Orange County's most heavily populated areas.

Friday's purchase agreement supports a plan developed by Orange County transportation officials to provide rail service to 10 cities in Orange County, stretching south to San Clemente.

"We think this is excellent!" said Dana Reed, chairman of the Orange County Transportation Commission of the purchase that now allows the five-mile segment to be joined with the 4.5-mile stretch of right of way that extends south to Santa Ana. The southern section is already owned by the Orange County Transit District, the county's primary public mass transit agency.

"It's now just a matter of laying the tracks and building the stations," Reed said. "I don't see why we can't be fully operational in five years."

But Reed said that timetable depends almost entirely on millions of dollars in operating funds dependent on voter approval of Measure M, the proposed half-cent Orange County sales tax hike for transportation improvements on the Nov. 6 ballot.

"If they do want these projects," Reed said, "this (Measure M) is the way to do it. The next step is passage of Measure M, and we start laying the tracks."

Some opponents of Measure M argue that public rail transit is too costly.

But Adrienne Brooks, manager of the OCTC's rail program, said Friday's announcement provides "exciting possibilities" for moving great numbers of Orange County residents back and forth to Los Angeles.

If operating funds become available, Brooks said, selection of a rail technology and an environmental impact study will follow.

The fact that rail service was once provided on the old Pacific Electric right of way could speed environmental approvals, Brooks said.