Narrows project inches along

The Sonoma-Marin Narrows got a little bit less narrow this week.

Transportation officials opened the first new carpool lanes on Highway 101 since 2013 - great news for southern Sonoma County commuters who associate Petaluma with traffic bottlenecks.

The new lanes, from the Petaluma River to the county line, open up a chronically clogged stretch of freeway, but it leaves more work to go in order to realize the vision of creating a continuous carpool lane from Novato to Windsor.

For the time being, the new 4-mile stretch of carpool lanes will be part of a confusing maze for drivers. Heading south, motorists will go from three lanes south of Cotati to two lanes through Petaluma, then three lanes at the newly widened stretch south of the city and back to two lanes at the county line ?before Highway 101 opens up to three and four lanes in Novato.

To solve this complicated mess, two gaps remain - just to the north and south of the new stretch of lanes.

Drivers will notice that the section through Petaluma is already under construction. Using local sales tax money along with the new state gas tax increase, transportation officials in ?October kicked off the $121 million project that will complete the Sonoma County section of carpool lanes.

The 3.3-mile section from Corona Road to the Petaluma River should be complete by the end of 2022. Crews have already started working on paving in the median and building sound walls north of Caulfield Lane, which should be complete by this time next year.

The biggest challenge of this project is a new overhead structure that will accommodate a new Rainier Avenue undercrossing. That will take most of the three-year construction schedule. The project will also remake the East Washington Street interchange and help with traffic on Petaluma streets.

The focus now turns to the Marin County side of Highway 101 and the last remaining bottleneck in the Narrows. Southbound, there is a 6-mile gap in carpool lanes from the county line to central Novato. Northbound, the gap is only three miles. This is because Marin officials several years ago pushed the northbound bottleneck nearly to Olompali State Park - out of the way for Novato residents, but still very much in the way for commuters continuing on to Sonoma County.

The northern reaches of Marin’s Highway 101 segment have always been terra incognita for our friends to the south as very few Marin County residents live north of Novato.

Yet commute patterns show that plenty of Marin residents work in Sonoma County and vice versa, so Marin County has an incentive to complete its section of the Narrows. Fortunately it looks like Marin County transportation officials are serious about finishing the job.

Officials plan next year to go after a pool of funding from the state gas tax increase - the same source that funded the lanes currently under construction through Petaluma. If they are successful, the project could start in early 2021 and finish a year after the Petaluma section.

Besides easing traffic for commuters, expanding Highway 101 has also been about reducing greenhouse gas emissions. The high occupancy vehicle lanes encourage carpooling, taking vehicles off the road. Combine that with new bike lanes and less time idling in traffic and the project is helpful in our effort to combat climate change.

That’s something residents of both counties can support.