Route 116 - Lakeville Hwy and Stage Gulch Road Intersection
In summer 2025, Caltrans is scheduled to begin construction of a roundabout at the intersection of Stage Gulch Road and Lakeville Highway south of Petaluma in Sonoma County. The roundabout will replace an existing three-legged intersection where Stage Gulch Road and Lakeville Highway converge in the semi-rural area of Lakeville south of Petaluma. Construction should be completed by spring 2027.
A note about road ownership might be helpful here. State Route 116 runs westerly as Stage Gulch Road until it meets Lakeville Highway. At that point Stage Gulch Road ends, but SR-166 continues, running northerly as Lakeville Highway. The portion of Lakeville Highway south of the intersection is a county road.
As traffic has markedly increased over the past decade, congestion has increased at this intersection that in currently controlled with a stop sign. Broadside collisions involving left-turning vehicles on State Gulch Road and northbound Lakeville Highway traffic has become a particular problem that can only be solved by signalization or reconfiguration of the intersection.
Design History
Caltrans completed two preliminary designs, which were shown at a public meeting April 2023. Each plan would reduce congestion and increase safety 
at the intersection of Lakeville Highway and Stage Gulch Road in Sonoma County just west of Lakeville.
In one alternative, Caltrans would build a roundabout that would slow down cross-traffic and meter traffic in all directions, making the intersection safer and eliminating the challenging left turn scenario where motorists feel they need to accelerate through cross-traffic lest they miss their opportunity to turn.
The other alternative was more modest, involving the construction of a new signalized left turn pocket on westbound Stage Gulch Road. This solution would be cheaper and make fewer traffic operational improvements but still fix the biggest problem of left-turning traffic.
The plan to construct a roundabout was chosen after a public meeting in April 2023.
Click Image Above to Explore
- Click on image to see existing roadway. Right click and hold to move image and explore
- Click explore the project to see Alternative. Click Alternative 2 to explore Roundabout Project
Caltrans will build a 180-foot circular roundabout centered 15 feet southeast of the existing intersection, featuring a continuous northbound right-turn bypass lane at the south leg of the intersection, and an 8-foot wide shared-use paths and curb ramps adjacent to the roundabout. The roundabout will also provide access to pedestrians and bicyclists.
Caltrans chose the roundabout over other designs as statistics indicating superior crash reduction rates due to fewer traffic conflict points and slower speeds. The new configuration will also reduce traffic backups at the intersection of Lopes Road.