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San Mateo’s Highway 101/92 Interchange Eyed for Expansion


San Mateo County’s transportation agencies are forging ahead with environmental studies of new lanes, ramps, and overpasses to add to the already massive interchange at Highways 101 and 92 in the city of San Mateo. Building on four previous studies stretching back to 2001, a new $500,000 study completed in June analyzed 25 different traffic expansion projects to remedy the interchanges “deficiencies” in carrying huge traffic volumes.

“Here's a list of four short-term projects for $14 million, or we could start making investments in longer-term solutions,” explained county Transportation Authority (SMCTA) Director Joe Hurley to the agency’s Board of Directors last Thursday. “Based on how you want to package them, you could go with a $146 million project or you could go as high as a $353 million project.”

The “solutions” identified as winners by SMCTA include widening the existing partial cloverleaf on-ramps to two lanes, building new “direct connector” overpass ramps or adding new Highway 101 frontage roads and on-ramps [PDF]. The potential of the proposed traffic expansions to fix safety hazards that motorists currently face in navigating the interchange was also evaluated.

“I think it's important to point out that these dollar amounts far exceed the capacity that Measure A has to even come close [to funding],” noted Hurley at the meeting. SMCTA plans to continue allocating a generous 27.5 percent of Measure A sales tax revenues to highway projects, despite the expansions all having failed to reduce traffic congestion so far.

For an estimated $93 million San Mateo could expand the 101/92 interchange with new carpool lane flyover ramps. Image: SMCTA, C/CAG
For an estimated $93 million San Mateo could expand the 101/92 interchange with new carpool lane flyover ramps. Image: SMCTA, C/CAG
For an estimated $93 million San Mateo could move even more traffic through the clogged 101/92 interchange with new HOV lane flyover ramps. Image: SMCTA, C/CAG

“These worked great many years ago when the traffic volume wasn't so heavy,” said Hurley of the three adjacent interchanges along Highway 92 located within a span of just one mile (Highway 101, Delaware Street, El Camino Real). “When you continue to load the system, it starts to break down.”

But loading the system with even more traffic is exactly what the SMCTA-funded reconstruction of the interchange at Highway 92 and El Camino Real (one mile to the west) will do when finished by 2018. With widened off-ramps and two new intersections, that expanded interchange will carry more vehicles per hour, thus funneling more traffic into the Highway 101/92 interchange.

More traffic going into more lanes for hundreds of millions of dollars rather than investing in potential transit solutions is sadly still business as usual in San Mateo County. SMCTA even disqualifies highway projects for funding that include safety components such as pedestrian bridges, arguing that Complete Streets requirements don’t apply to projects funded by its Highway Program.

As state and regional funds for highways dry up and construction costs continue to escalate, the Transportation Authority is finding that its Measure A sales tax won’t buy as many highway expansions as the agency had hoped for. Last year SMCTA created a ten-year Highway Capital Improvement Program (CIP) to assess the total “need” for traffic expansions on highways in San Mateo County. The agency estimates it will be able to build about half of the $1.3 billion worth of highway projects listed [PDF] in the CIP using Measure A and other funding sources by the time the tax measure expires in 2033. This figure doesn’t include the planned expansion of Highway 101 with Express Lanes that would cost several hundred million dollars more.

The City of San Mateo has not yet decided to seek funding for any of the options analyzed in the June 2016 study. SMCTA distributes highway funds every two or three years using a competitive grant process, most recently spending $108 million on eight projects in October 2015.

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