MTC analysis confirms: Optimized HOT is the best choice for Highway 101
Clarrissa Cabansagan Headshot

 GarrettMoving more people with less traffic – it sounds almost too good to be true.  But for the past few years TransForm has been convinced that it’s possible to reduce congestion on the Bay Area’s most crowded freeways without pouring more concrete. We call this innovative approach “Optimized HOT.”

An express lane (also known as a high-occupancy toll, or HOT lane) is a highway carpool lane that solo drivers can pay to use.  An Optimized HOT express lane would use tolls to fund transportation options that make commuting faster, safer, and more affordable for all people who travel along the corridor.

Now, a new analysis from the Metropolitan Transportation Commission (MTC) confirms that Optimized HOT is the best choice for Highway 101 in San Mateo County, and could be the key to relieving gridlock on one of the worst stretches of highway in the nation. MTC’s analysis shows that Optimized HOT can be completed sooner, move people faster, cost less, and create less pollution than current plans to build a new HOV lane.  

This is great news for commuters, employers, public transportation riders, taxpayers, and other regions seeking cost-effective and equitable strategies for reducing traffic.  If San Mateo County implements Optimized HOT, it will set a new bar for how express lanes can create more transportation options and maximize congestion reduction for the long term.

That’s why TransForm has been promoting the Optimized HOT approach for the past several years. We’re encouraging agencies to ensure the Bay Area’s Express Lane Network goes as far as possible to increase transportation choices, minimize costs, and share the benefits fairly.  We’re thrilled to see that MTC’s new analysis supports our approach.

Desperately seeking solutions for Highway 101 in San Mateo County

California Assemblymember Kevin Mullin (D-San Mateo) points out that Highway 101 between San Francisco and San Jose is “the most economically productive and important highway corridor in California.”

Highway 101 is also home to the Bay Area’s three most congested highway segments, and they’re only getting worse.  Everyone – from solo commuters to carpools to tech shuttles – is moving at a snail’s pace.

So it comes as no surprise that some of our region’s largest employers, represented by the Bay Area Council, have increasingly called on our agencies to find quicker solutions to the gridlock. They’re asking for traffic relief sooner than would be possible with the current plans to widen highways.

This push, inspired in part by TransForm’s initial proposal for Optimized HOT in our 2013 report Innovation Required, helped motivate the region’s transportation leaders to take a closer look at how to tackle Highway 101’s traffic problems.  

MTC’s analysis relied on an intensive data collection effort by MTC and a detailed analysis that went beyond the analysis in Innovation Required.  MTC’s analysis looked at key components of the Optimized HOT approach, including:

  • Converting existing lanes to express lanes or high occupancy toll lanes;
  • Using toll revenues to boost transit service and an equity program for low income travelers in the corridor; and
  • Implementing policies and strategies that encourage less driving. 

MTC documented this analysis in a presentation given to agency officials and employers in late June, entitled “San Mateo 101 Corridor Strategies: An Innovative Partnership in the Making.”  The following provides a summary of key findings from MTC’s analysis, illustrated with slides from the agency’s presentation. For a copy of MTC's full presentation, click here.

**Wonk alert!  We believe it’s important to share the details of MTC’s study. We’ve tried to use non-technical language as much as possible, but some of what follows is still pretty complex.

Key findings from MTC’s analysis

1. San Mateo’s current plans will not work. For several years, San Mateo County has been studying what they call a “Staged Hybrid HOV” proposal – widen the highway to provide a two-passenger carpool lane (HOV-2+). MTC’s analysis shows that the new lane would be congested from the day it opens. Worse, county and Caltrans reports suggest it would take nearly a decade to complete (although Caltrans reportedly is trying to shorten that timeframe)

The chart below shows that there would be too many vehicles attempting to use the carpool lane: the lane would be “degraded” upon opening. This means that cars in the new carpool lane would have little to no time advantage over cars in the other lanes. [Slide 6, “HOV-2+ is not an option”]

Slide 6: HOV-2+ is not an option

2. San Mateo County residents want more transportation options. Because of budget cuts, SamTrans had to slash express bus service in 2010 and 2014, eliminating all but one express bus route on the peninsula.  As a result, weekday SamTrans express bus ridership to San Francisco plummeted from more than 6,000 riders in 2002 to fewer than 1,000 in 2015. Caltrain is pushing the limits of its capacity, and its most crowded stations are in San Mateo County. [Slide 3, “Caltrain at Capacity & Demand Growing” and Slide 4, “SamTrans SF Express Service Cut"]

When there’s no room on the train and only a few available express buses, residents have to resort to driving.

Slide 3: Caltrain at capacity and demand growing        Slide 4: SamTrans SF express service cut

3. Too many people are driving alone. Currently the overwhelming majority of rush hour traffic on Highway 101 in San Mateo County is from solo drivers: 75% of vehicles carry only 52% of the people. At the other end of the spectrum, buses, vanpools, and three-person-plus carpools make up less than 3% of the vehicles during commute times – but carry over 20% of the people. This is inefficient use of our highways. [Slide 8, “Significant Existing HOV & Private Transit”]

Slide 8: Significant existing HOV and private transit

MTC’s analysis shows that, on average, there are currently 30 passengers per bus.  Each van can relieve the space needed for eight cars!

Thesame number of passengers on one bus would fill a whole city block if they were to drive alone.

4. MTC analyzed all options, and concluded that Optimized HOT is the best solution for congestion and cost.  The following chart shows congestion levels today (far left) and then how those levels would change based on several scenarios (which they call “steps”). The chart shows the number of cars per hour traveling in the four lanes of Highway 101 at one point (Ralston Avenue) at the most congested time of day. [Slide 9, “Applying All Options = Feasible Project”]

Slide 9: Applying All Options = Feasible Project     

This is the most complicated slide in the presentation, so let’s walk through it together:

a. The first two sets of columns show current traffic levels (“Existing Lanes” = actual traffic in each lane, while “= Existing” shows lanes 2-4 averaged together). Note also that this graph shows different colors/patterns for different types of vehicles, shown in the legend to the right.  

b. Step 1 in the chart shows what would happen to congestion levels if the existing leftmost lane were converted into an HOV-2+ carpool lane (requiring two or more people per car). The result would be less congestion in the new carpool lane (B) but more congestion on all other lanes, since solo drivers would no longer allowed in this lane (C).

c. Step 2 shows what would happen if the leftmost lane were converted to a carpool lane that instead required three or more people per vehicle (HOV-3+), as is currently the case on I-80 along the East Bay. Fewer cars would form HOV-3+ carpools, so the new carpool lane would appear empty (D), pushing cars to the remaining lanes (E). This would create levels of congestion much worse than the current gridlock.

d. Step 3 introduces pricing: it would add tolling to the carpool lane, transforming it into a high-occupancy toll lane. Solo drivers and two-person cars would be able to buy their way into the lane (shown in the chart as “tolled vehicles”). This would allow the new express lane to be more effective at moving vehicles, but it is not enough. Traffic in all other lanes would still be worse than existing conditions (G).

e. Step 4 adds transit and Transportation Demand Management (TDM). In this step, not only would the existing lane be converted to an express lane, the toll revenues would also be used to boost transit service and encourage alternatives to solo driving. This option would depend on employers instituting policies to discourage solo driving and add more private and public shuttles. This step’s benefits would be strengthened if the tech community encourages people to form carpools using ride-matching apps. MTC estimates that a combination of all of these efforts would result in a 10-15% shift of current solo drivers to carpools and transit. It would also reduce current congestion levels in all other lanes by 5% compared to existing conditions (H).

5. Which approach offers the most traffic relief, is cheaper, and can happen sooner? Optimized HOT! MTC uses the “Steps” described above to evaluate how three strategies measure up in terms of traffic reduction, time to complete, and cost.  Only one strategy succeeds on all three counts: Optimized HOT, AKA strategy “B” in the table below.  [Slide 11, “What Passes the Litmus Test?”]

Slide 11: What Passes the Litmus Test?

Here’s a summary of how they measure up, according to MTC:

A) Staged Hybrid HOV: Add a new carpool lane by widening the highway

a.    Less congestion  but only temporarily -> FAIL
b.    Complete in 2023 or later -> FAIL
c.    Costs $250M -> FAIL

B) Optimized HOT: Convert an existing lane to an HOT 3+, use toll revenue to boost transit service; and work with the business community to implement strategies that increase carpools and encourage transit and shuttle use.

a.    Likely better congestion levels -> PASS
b.    Complete in 2018 -> PASS
c.    Costs $140M -> PASS

C) The combo approach (A+B): Add a carpool lane by widening and then convert to an express lane

a.    Some improvement in congestion ->PASS
b.    Partially complete in 2018; fully complete in 2023 or later -> Partial PASS
c.    $390M -> FAIL


Overall, MTC's analysis shows that converting a general purpose lane to HOT and using the revenues for transit + TDM can be done sooner, have less traffic, cost less, and move more people with less pollution than current plans to build a new HOV lane.

Working together, MTC, and San Mateo County have a tremendous opportunity to make Highway 101 work much better. They have already started to make significant strides towards implementing components of Optimized HOT. Most recently, MTC invited the private sector to submit proposals to produce a more effective version of, the region’s database for ridematching commuters looking to carpool. App-based ridesourcing companies such as Lyft and UBER, and new entrants such as Carzac, Carma, HellaRides, and others are all looking for ways to create a carpooling market among solo drivers.  MTC is also considering taking a comprehensive look at all highways in the Bay Area to determine where else this approach might be viable. 

At TransForm, we’re very excited to see MTC’s analysis show not only that the Optimized HOT approach can work, but that this approach is the best solution for congestion relief on the 101 corridor. This is especially important since two-thirds of Bay Area residents continue to drive solo to work each day, a statistic that hasn’t budged for decades.

TransForm is committed to working with San Mateo County agencies and leaders and with MTC, the business community, and other key stakeholders to ensure the best outcomes for Highway 101!

Read MTC's full presentation here.

See our factsheet here.

FeedBlog Signup

About This Blog

TransForum is the blog of TransForm, California's leading transportation advocate. For more about our work, including ways you can take action and contribute, visit