[caption id="attachment_55013" align="alignright" width="364" caption="Work in the Narrows area includes improvements to a freeway overpass originally constructed for landfill vehicle use."][/caption]

MARIN and SONOMA COUNTIES – Drivers commuting between Sonoma and Marin counties are on track to save more than 10,000 in total delay hours per day after the California Transportation Commission voted last week to allocate more than $110 million to two Highway 101 improvement projects, narrowing a funding gap to improve travel between both counties, according to the commission.

The work will focus around an often congested, two-lane stretch between the counties known as the “Marin-Sonoma Narrows,” eliminating a number of roads that slow traffic by providing direct access to Highway 101 and creating new interchanges and freeway crossings.

The larger of the two allocations – $82 million – will help fund the construction of a new bridge over the Petaluma River in Sonoma County, as well as a new interchange at Petaluma Boulevard South, frontage roads and equipment for ramp metering. Construction is expected to last two years, at a total cost of $123 million.

The second -- $29.7 million – will help fund the construction of new frontage roads and a new interchange for San Antonio Road in Marin County, a $78 million project near the Redwood Landfill north of Novato.

The allocation brings the total funding obtained for the long-term overhaul of Highway 101 through northern Marin and Sonoma County to “about 80 percent” of a required $976 million, with a number of elements already completed since the first groundbreaking in 2001, said Sonoma County Transportation Authority Director Suzanne Smith. Other funding has come from state and federal sources, including $141 million from Sonoma County’s Measure M, passed in 2005.

 The authority is currently seeking state and federal sources to bridge the remaining $177 million funding gap, which will afford the construction of high-occupancy vehicle lanes through Petaluma and into the Narrows area, Ms. Smith said. That construction is the final piece that the commission calculates will substantially alleviate traffic in the frequently congested stretch of Highway 101.

Traffic and safety improvements are still expected before the widening, as both projects will eliminate a number of intersections that allow drivers to turn directly onto the highway. Instead, frontage roads will direct drivers to the new interchanges, allowing smoother access to traffic and expanding an existing freeway overpass constructed for use by landfill vehicles.

An extension of HOV lanes on the Marin side of the Narrows, northbound between Highway 37 to north of Atherton Boulevard and southbound between Highway 37 to Rowland Boulevard, is already under construction and expected to be completed in 2013, according to the Transportation Authority of Marin.

Outside of the narrows, new HOV lanes have shown to have an impact on commute times for North Bay drivers. With the 2011 completion of Marin’s Gap Closure Project that created 17 miles of continuous HOV lanes south of Highway 37, southbound delays in the HOV lane were reduced from 22 minutes to five minutes. Northbound delays for carpool drivers were reduced to 1.5 minutes from 5.5 minutes, and commute time decreased by 55 percent in the other lanes, according to the Transportation Authority of Marin.

New HOV lanes are also expected to open in Sonoma County later this year, providing a continuous stretch between Petaluma Boulevard North and Windsor, Ms. Smith said.

The Commission also approved $24.1 million in April to fund the construction of a new interchange at Airport Boulevard in Sonoma County, with that work expected to break ground in September, Ms. Smith said.