FRENCH VALLEY -- Transportation officials are about to launch the final leg of a long-running campaign to improve one of Southwest County's most traffic-clogged arteries: Winchester Road.

The county has been working for years to widen Winchester Road north of Murrieta Hot Springs Road. Now the county is preparing to build the final $42 million piece, which will deliver an 8-mile-long ribbon of asphalt four lanes wide -- with turn lanes -- between Thompson Road and Domenigoni Parkway by 2010, county Transportation Director George Johnson said Friday.

Following a Riverside County Board of Supervisors vote next week to secure $6 million in local funding for the project, the work is expected to start in late October, Johnson said.

"This is a very important project," he said Friday. "It is a primary north-south regional corridor, and this will help improve mobility and reduce congestion."

Weary Winchester Road travelers have been waiting patiently, and sometimes not so patiently, for the county to deliver relief to a corridor that saw explosive population growth during the recent housing boom.

"Tell them to hurry the hell up," said Steve Lowe of Temecula, who often takes his motorhome on Winchester en route to recreational destinations in the desert.

"They absolutely need to stop everything else and finish that road," Lowe said. "You take your life in your hands every day you drive it. … It's scary. People are always in a hurry and they are trying to pass when there is nowhere to go."

And it doesn't help that, because of the hodgepodge of improvements next to scattered housing tracts, the road is anything but seamless, he said.

Indeed, north of Thompson the road abruptly goes from two lanes to six lanes to two lanes, then to four and back again to two -- in little more than a mile.

The frustrating thing, said Joe Diorio, owner of French Valley Aviation and longtime French Valley resident, is the county knew two decades ago that Winchester needed attention. Diorio recalled that, in a 1986 community meeting, county officials stated that the coming growth would require a six-lane thoroughfare.

Clearly, Lowe said, "We have outgrown our road system."

Johnson said the county is trying to catch up with the growth. In a few weeks, construction will begin between Thompson and Whispering Heights Parkway, south of Scott Road. The work should be completed in four months, Johnson said.

In early 2009, he said, work will get under way north of there and reach Domenigoni in about a year. The project is being financed with a combination of sources, including $20 million in federal funds.

On Tuesday, the Board of Supervisors will consider an agreement with the Riverside County Transportation Commission that would free up $6 million from a special developer fee known as the Transportation Uniform Mitigation Fee.

Contact staff writer Dave Downey at (951) 676-4315, Ext. 2623, or ddowney@nctimes.com.