A third lane on the Richmond Bridge is just a bandage

from MTC

from MTC

The push for a third lane to Richmond has sucked a lot of the air out of the conversation over Central Marin traffic. Cut-through drivers from San Francisco to Richmond are taking up all the space in Larkspur and causing horrific traffic. Thanks to induced demand, however, the third lane will likely fill up soon after it opens and we’ll be back to the same old story.

The most common way to think of traffic is as a gas that fills the space it’s given. No matter how much you build, there will always be traffic to fill it. This couldn’t be more apt for the situation faced by the Richmond Bridge.

Right now, for cut-through San Francisco-to-East Bay commuters, the Marin route is the fastest and cheapest way to get home. These drivers may have to deal with congestion and delays on Sir Francis Drake and 580, but it’s less than what they’d have to deal with on 80 and the Bay Bridge.

If we solve the problem and open a new lane on the Bridge, we’d reduce congestion in Marin enough that we could declare victory… until more people saw that it was a less-congested route than 80 and the Bay Bridge and switched. Either this area will return to its present levels of congestion, or the congestion will migrate to another bottleneck further south in the system, or some measure of both.

This is a much larger version of a problem faced by Los Angeles suburbs, where cut-through drivers, guided by their GPS, take surface streets to escape congestion on freeways. Delays become as bad on surface streets as on the freeway.

If congestion returns to Larkspur Landing, then the widening will simply buy us a few years of peace. If it causes another bottleneck, we’ll have bought some peace to Larkspur Landing at the cost of congestion elsewhere. If it’s both, then nobody wins.

Longer-term solutions depend on which outcome occurs; let’s look at each in turn.

Congestion comes back to Larkspur Landing only

If this occurs, the only real solution is to keep traffic on the freeway as long as possible by installing a proper 101-580 interchange in San Rafael. This interchange has been proposed before, but community opposition to a towering flyover connecting westbound 580 with southbound 101 scuttled the project. If the same opposition arises again, it might be worthwhile to simply remove that aspect and only do the eastbound 580 to northbound 101 aspect.

For now, at least, Caltrans ought to remove signs at the Sir Francis Drake Boulevard exit indicating that that is the way to 580.

Congestion occurs elsewhere in the system

The most likely location for congestion to occur is south of Marin City: on the Waldo Grade, Golden Gate Bridge, Lombard, or Van Ness, all of which are good targets for transit. Both Marin commute trips and local San Francisco trips are relatively easily served by transit. The upcoming Van Ness BRT line will make a big difference to that corridor, and an extension onto Lombard would help both GGT and Muni riders. Extending the HOV lanes onto the Waldo Grade by converting one of the through-lanes would speed transit and encourage carpooling, also helping alleviate congestion.

Alas, transit sometimes functions like adding more lanes: the amount of congestion stays constant even while the transportation capacity of a road to move people increases. At least we can comfort ourselves that fewer people will experience congestion from behind the wheel.

Congestion occurs both at Larkspur Landing and elsewhere

If this occurs, then planners will need to employ both solutions: add the interchange and improve transit.

The only permanent solution

The rub, of course, is that congestion is ultimately not a solvable problem without an economic downturn. Houston, Seattle, Los Angeles – all have tried to fix congestion by increasing roadway capacity, and none have succeeded. Anthony Downs, in his 1992 book Stuck in Traffic, said that widening a freeway doesn’t work thanks to what he called a “triple convergence”:

In response, three types of convergence occur on the improved expressway: (1) many drivers who formerly used alternative routes during peak hours switch to the improved expressway (spatial convergence); (2) many drivers who formerly traveled just before or after the peak hours start traveling during those hours (time convergence); and (3) some commuters who used to take public transportation during peak hours now switch to driving, since it has become faster (modal convergence).

The only way out is to view road space like a resource, and to price it as such. Jarrett Walker describes it thus:

Fundamentally, congestion is the result of underpricing.  If you give away 500 free concert tickets to the first 500 people in line, you’ll get 500 people standing in line, some of them overnight.  These people are paying time to save money.  Current prevailing road pricing policy requires all motorists to act like these frugal concertgoers.  Motorists are required to pay for road use in time, rather than in money, even though some would rather do the opposite and our cities would be safer and more efficient if they could.  Current road pricing policy requires motorists to save money, a renewable resource, by expending time, the least renewable resource of all.

For the Bay Area, this would mean varying bridge tolls during the day so that congestion never builds up. Downs’ triple convergence would work in reverse.

With a rush hour 80 and Bay Bridge free of congestion, cut-through travel would be much less attractive for Contra Costa commuters. Those that still made the journey would likely not be enough to congest 101 at all.

But before then, we have a third lane and an interchange to try.

About David Edmondson
A native Marinite working in Washington, DC, I am fascinated by how one might apply smart-growth and urbanist thinking to the low-density towns of my home.

14 Responses to A third lane on the Richmond Bridge is just a bandage

  1. Richard Hall says:

    Funny, as I read this article I found myself checking out the Anthony Downs “triple convergence” article as it is very apropo. I was happy to see you quote this:

    Click to access Access%2025%20-%2004%20-%20Traffic%20Congestion%20is%20Here%20to%20Stay.pdf

    However you misconstrue the benefit of widening, writing it off as the extra capacity will be filled as if that means it is not worthwhile. That extra capacity is pent up demand for economic activity that has been suppressed.

    I agree that the 101-580 interchange is very much required. I believe there’s an issue that if you can exit from one direction you must exit from the other, and one exit direction is particularly challenging to build. What’s worse is that SMART, with the aid of Gary Phillips, exploited the debate over the Greenbrae interchange, waltzing away with money earmarked to solve this issue affecting hundreds of thousands of car occupants for the sake of at best 500 train riders (in fact 251 in 2035 if the latest EIR for the Larkspur extension is to be believed, perhaps that’s 125 riders since the 251 may be trips). The train is cannibalizing genuinely needed projects – and has just now issued a call for $225m more for the sake of a handful of riders 20 years in the future!

    • I’m not saying the extra capacity will be filled and that’s a bad thing in and of itself, I’m saying that if our aim is to eliminate congestion then the extra capacity won’t help.

      In fact, though it’s outside the scope of this piece, to optimize the new capacity we may want to create it as an HOV rather than general purpose lane. This would encourage carpooling for East Bay to Marin trips and – bonus! – speed the 40 and 42 buses.

      • Richard Hall says:

        Just so long as we consider that an HOV lane adds capacity around 1,200 cars / hour vs a regular lane at 2,000 cars / hour.

        I’m just tired of reading that because the extra capacity will be filled that’s bad, so why bother, when this dismisses the considerable incremental benefit via economic activity…

        • We’d only be concerned about car capacity if we want to use the bridge for car storage during peak hours. If we want more economic benefit of the capacity, then we want to maximize trip capacity instead.

          At peak hours, stop-and-go freeway traffic (average speed of 15 mph) has a capacity of about 1,300 vehicles per hour (VPH). Given that average persons per vehicle at rush hour is about 1.2 (it’s 1.6 for the whole of the day), that gives a three-general-purpose-lane Richmond Bridge roughly 4,680 trips per hour, assuming traffic flow is still slow for about an hour.

          Swapping one general-purpose lane for an HOV-2 lane (throughput of about 1,200 VPH) will get us about 5,520 trips per hour on the bridge, a difference of 840 over the three general-purpose lane model.

          For the record, a road-priced bridge with two general lanes would have a rush-hour capacity of 5,040; with three it would be 7,560.

          • Thank you for that information about optimizing trip capacity, especially the detailed numbers. Could you tell us where to find those calculations and how they are made? I am not disputing them, but I have found that the first thing we human beings do when confronted with data is to dispute it’s factual accuracy. So how could I, for instance, explain that data’s derivation to my relatives who are generally pro-road widening and anti everything else?

          • @voltairsmistress

            Some of this I just have committed to memory, but I’ll dig up my original sources. Much of it is from capacity studies done on HOV lanes in Los Angeles.

          • Richard Hall says:

            Insight from a transportation expert I’m connected to:

            “You can generally do about 1,600 cars/lane/hour before you start getting into Level of Service F. At 2,000, you are probably in LOS F, but it is possible under some situations to not get into stop-and-go – but, it is so close, the smallest negative would put over the tipping point.”


            Levels of Service:
            D: approaching unstable flow. Speeds slightly decrease as traffic volume slightly increase. Freedom to maneuver within the traffic stream is much more limited and driver comfort levels decrease

            E: unstable flow, operating at capacity. Flow becomes irregular and speed varies rapidly because there are virtually no usable gaps to maneuver in the traffic stream and speeds rarely reach the posted limit.

            F: forced or breakdown flow. Every vehicle moves in lockstep with the vehicle in front of it, with frequent slowing required. Travel time cannot be predicted, with generally more demand than capacity. A road in a constant traffic jam is at this LOS, because LOS is an average or typical service rather than a constant state.

          • @voltairesmistress

            “The Freeway Congestion Paradox” is a pretty good source. It’s where I got the 1,300 vehicles per hour at congestion and the 2,000-ish maximum capacity of a general-purpose lane. The Legislative Analyst’s Office has a report that cites an average person-flow on an HOV lane of 2,518 persons per hour, slightly higher than my estimate of 2,400 persons per hour. I’d go with that.

            As for road-priced capacity vs. status quo, this assumes high volumes and free-flow traffic at or near the 2,000 VPH capacity.

        • John Murphy says:

          Richard – history has not really shown that what we get is extra economic activity – unless the extra economic activity you seek is “building extra housing in the exurbs”. Sacramento added freeway capacity on US-50 east of Folsom, to facilitate the building of housing in El Dorado Hills. Unless one presumes there is no possible way to build the housing required for overall economic growth closer in to Sacramento – this is a net negative for economic growth. El Dorado Hills has grown to the point where the freeway usage expanded to the point where US-50 is badly congested again, but now we have a large population that owns houses on the wrong side of the congestion from their jobs. So they have to suck it up in traffic.

          The net effect is that those people now have *reduced* benefit on the economy of their region as they have no choice but to have a longer commute than had Sacramento chosen to expand their housing closer to their job centers. Those citizens now spend an extra 90 minutes a day in their car then they otherwise would have, because they bought housing based on the premise of a speedy commute that only existed for a brief moment in time until the housing produced re-congested the freeway. The only economic benefit now is accrued by Exxon and OPEC.

          • Richard Hall says:

            @John – please do take a read of the July 2013 UK government white-paper:

            Click to access action-for-roads.pdf

            This states: “Roads are key to our nation’s prosperity…Better roads allow us to travel freely, creating jobs and opportunities, benefiting hardworking families across the country.”

            It continues: “We need to maximise every one of our economic advantages, and deal with every factor that holds us back if we are to succeed in the global race. Transport is one of the most important factors in making our country prosper. As a densely-populated island, we should benefit from being better connected and more compact. This government has already committed to a major transformation of the rail network. However roads remain the most heavily used mode of transport for people and businesses and we need to give them the same attention.”

            “Failures of the road network increase costs, stifle employment opportunities and make it harder to do business”

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  3. stephen nestel says:

    So you are proposing that workers in the East Bay pay an extra tariff to pay for the crime of driving across a body of water during rush hour? Yea, That will work. It will price workers out of the city. You’ll get your dream of an economic downtown. [Removed for violating comment policy]

    Part of the problem is the view, that economic development must happen in crowded urban areas. This is so nineteenth century. The greenest commuters work in suburban parks, satellite offices or from home. It used to be this way in Marin too.

  4. Stephen Nestel says:

    [Removed for violating comment policy.] Many workers in Marin live in Richmond and Hercules in homes they can afford. What right is it for anyone to penalize these hard working folks? You imagine that they will take a bus or carpool but that is
    Not realistic for everyone. In the end, such policies serve to enrich government through regressive taxation. Not “fair and affordable” housing for everyone.

  5. ziggythehamster says:

    I live in Richmond (near Pinole) and work in San Rafael. I would take the bus if I could park at BART without risking getting a ticket because I’m not riding BART (and it would be stupid to park at del Norte and BART to Richmond to transfer to GGT). I’d bike, but the grade on the way back is way above my fitness capability :).

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