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101 express lanes project (SF Bay Area)

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I couldn't find an existing thread about this; please merge if there is one.

The 101 express lanes project adds a new express lane from I-380 to Whipple Ave in San Mateo County, and converts the existing HOV lane to an express lane from Whipple Ave to the SM-SC county line (and seemingly beyond, though maybe this is being managed separately). The new lane (Phase II) is expected to open in late 2022 while the existing HOV lane being converted to an express lane (Phase I) is expected to open in early 2022.

Question: from what I can tell from the documentation, this will result in 5 through lanes (including the express lane, so 4 general purpose) from I-380 to Whipple, but from Whipple to the county line there will be only 4 through lanes. (Sometimes there is a fifth lane, e.g. SB from Whipple to the Woodside Rd exit, but this is more of an auxiliary lane.) Why are they only adding a 5th lane for part of the peninsula? Seems weird that 101 will have 5 lanes from I-380 to Whipple and again from the county line to 85 (5th lane / second HOV lane already exists here), but with a "gap" from Whipple to county line where no new lane is added. Was this due to some infrastructural limitation or is it by design due to lower traffic demand in that stretch?

Hypothesis: there was a requirement to not reduce the number of general purpose lanes at any location. Therefore, the new lane *had* to be added north of Whipple since they didn't want to convert an existing general purpose lane to an express lane. Whereas south of Whipple the #1 lane is already HOV-only so it was not an issue to convert it to express lane.

I get this, but it still seems weird to construct a fifth lane all the way down but stop at Whipple. Or am I overthinking it?


--- Quote from: FredAkbar on December 25, 2021, 01:28:56 AM ---Hypothesis: there was a requirement to not reduce the number of general purpose lanes at any location.

--- End quote ---

Yes, Caltrans has a policy of not converting general purpose lanes to HOV or HOT lanes.  Any new HOV/HOT lanes are the result of road widening and not the conversion of an existing general purpose lane.

In 1976, Caltrans converted the leftmost lane of I-10 between LA and Santa Monica to a carpool lane. There was a public uproar.  People dumped tacks in the carpool lane, others painted over the diamonds at night.  After 5 months the lane was changed back to a general purpose lane.  LA Times Article with more info.

The one exception is a pilot project in San Francisco, where one lane on city streets is being converted to an HOV lane.  US-101 on Lombard Street and CA-1 on Park Presidio Blvd have one GP lane (out of a total of three lanes each direction) converted to an HOV lane. 

--- Quote ---The project is a pilot which will last as long as the city is still under the COVID-19 state of emergency. After that is rescinded, SFMTA will have 120 days to analyze the success of the changes and determine if they will be removed or become permanent.
--- End quote ---

San Francisco is also proposing adding an HOV/HOT lane to the freeway portion of US-101 and I-280 by converting a GP lane, but that is still in the project scoping stages.

Plutonic Panda:
I wish San Francisco would convert the 101 to a freeway through town. Shit.

The Ghostbuster:
You would sooner see San Francisco tear down all their freeways before you would see one inch of new freeway (or even one new lane) constructed in the city of San Francisco. I think that would be true for the majority of inner segments of cities nationwide.


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