Fairfax-Bolinas Road in West Marin at milepost 5.73 (approximately 2 miles west of Azalea Hill) is single-lane access with two-way traffic controlled through one lane. This condition is at the construction zone only and will remain in place until project is completed. See project webpage for more details. Thank you for your patience while this project progresses.

Hairpin Turn on Lucas Valley Road to be Improved

Posted on April 15, 2021

For Immediate Release –

San Rafael, CA –

Traffic impacts expected during federally funded work to help problematic curve

hairpin turn on lucas valley road
The public safety project will significantly soften the sharp turn on Lucas Valley Road, which has been the site of several accidents over the years.

The Marin County Department of Public Works (DPW) will soon oversee the realignment of the hairpin curve on Lucas Valley Road at milepost 5.08 in West Marin, just east of the Big Rock trailhead. The public safety project will significantly soften the sharp turn, which has been the site of several accidents over the years.

The project is expected to enter the contractor bidding process on April 21. DPW staff expects construction work to begin in mid-summer and should be complete before the end of the year. It is anticipated that traffic will be affected throughout the project.

The estimated $2.25 million project is partially funded by a $1 million Federal Highway Safety Improvement Program (HSIP) grant. The remaining funds will come from the County’s Road and Bridge Rehabilitation Fund.


Lucas Valley Road is a key east-west connection from the highly populated Highway 101 corridor with more rural West Marin. In addition to passenger vehicles, the two-lane road is used daily by drivers of large trucks, often carrying agricultural supplies. Despite relatively low rates of speed on the twisting and hilly road, traffic accident rates are above average at the project location and, while the upcoming construction comes with unavoidable public inconvenience, the work provides significant safety improvements.

To improve safety and realign the hairpin turn, a 135-foot-long retaining wall will be installed on the downhill side of the turn at mile post 5.08. The retaining wall will then allow for the road to be shifted east, resulting in a less severe curve radius. The project also includes modifications to storm drain infrastructure and the installation of safety guardrail.

While the construction schedule and traffic plan will not be determined until a contractor has been selected, traffic impacts are expected. It is likely that the westbound lane of Lucas Valley Road will need to be closed for the duration of the project. If that is the case, all vehicles traveling through the project site will be limited to one lane. Alternating access for traffic would be controlled by flagging personnel or portable traffic signals at either end of the project limits.

Due to the physical constraints of the worksite, critical construction operations may necessitate several short durations of full road closures around milepost 5.08. As per standard procedure, emergency service vehicles will be allowed access. Any full road closures would be temporary and during the regular working hours. DPW and the contractor will provide advance notifications on any planned closures.

Bicycle access also could be intermittently prohibited through the project zone. Notifications of closures for non-motorized traffic would be made in advance and signage would be in place.

Improving roadway conditions across unincorporated areas of Marin has been an ongoing commitment of the County for years and is one of the top priorities for the Board of Supervisors.

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