The Novato Narrows

The stretch of US 101 between Novato and Petaluma, known as the Novato Narrows or the Marin-Sonoma Narrows, was until the 2010s a freeway in name only: a four-lane road with private driveways, a landfill entrance and side roads such as San Antonio Road and Kastania Road emptying straight onto it. By 2013 it carried 146,000 vehicles a day, 6,200 of them trucks. The crossing of San Antonio Creek marks the county line, and the two bridges there told the story: the northbound span was built in 1929, the southbound in 1947, and the low road beside the creek flooded from time to time. Dump trucks from the landfill and cars from homes and businesses joined the freeway straight out of their driveways. The Marin-Sonoma Narrows project rebuilt roughly seventeen miles of it in thirteen pieces over more than a decade, at a cost of about 761 million dollars, paid for by county sales-tax measures, the state, and the 2017 gas-tax increase. The highway was realigned to the west at the creek and raised out of the flood plain on a new bridge, the driveways and at-grade crossings were closed, and in June 2023 southbound traffic moved onto the elevated lanes. The last piece, a continuous carpool lane through the Narrows, opened on 29 September 2025, completing 58 miles of HOV lane from Sausalito to Windsor and a corridor programme that had run a quarter of a century and about 1.5 billion dollars. Suzanne Smith, the former director of the Sonoma County Transportation Authority, remembered the old road as dodgy: whether at Kastania, San Antonio Road or the landfill, there was a lot of direct access onto 101. Landscaping is scheduled to continue into 2027.