More people are speeding on the Golden Gate Bridge – here’s why

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The new barrier and the bridge during closure. Image by David Yu, on Flickr

When the new Golden Gate Bridge barrier opened, it was heralded as a new age of safety, but there were rumblings of problems immediately. Bridge Manager Kary Witt was quoted as saying, “I do think everyone is driving too fast. Everyone needs to slow down.” A few days later, he was rather more forceful: “We’re seeing too many drivers driving 20 to 30 miles over the speed limit. It’s completely unacceptable.” While the district seems to have been caught off-guard, this was an entirely predictable result.

Keeping roads safe is one of the most important tasks traffic engineers have. To do this, they will often try to improve a road’s safety by making it more forgiving of driver error: make the lanes wider, smooth out the curves, remove trees, and add median barriers. But this sort of improvement assumes that people drive a set way without regard to their environment.

This is not true. People drive as fast as feels safe, and they subconsciously react to visual cues to tell them what that speed is. Have you ever driven along a road at what felt like a comfortable speed, only to find that you were going 55 in a 35 zone? You were a victim of this subconscious pressure, called risk compensation.

By removing dangerous obstacles, engineers will often paradoxically make a road less safe by encouraging higher speeds. In a limited-access highway this might be okay, but on roadways that aren’t limited access – like the Golden Gate Bridge – it can create a dangerous false sense of security.

This is precisely what is happening on the bridge. Before, drivers on the bridge had a very visible cue that danger was omnipresent as traffic whizzed by in the opposite direction just a foot away. People would drive slower to ensure they had control of their vehicle and wouldn’t accidentally drift into traffic. They also had to navigate the very tight space between toll booths, slowing traffic further.

By removing the toll booths and adding the center barrier, the bridge district has lowered the perceived danger of crossing the bridge. This has encouraged drivers to drive faster, which has resulted in more crashes.

This is not a limited access roadway, either. There are driveway entrances and exits at the Toll Plaza and at Vista Point. Pedestrians and bicyclists cross the bridge on its sidewalks. This is a recipe for disaster.

It is perhaps understandable that the district would choose to spend millions on a median barrier. It was a harrowing crossing, and I know I never drove in the left lane if I could avoid it. But it is baffling that the bridge district was apparently unprepared for higher speeds as a result of this change.

There is a lesson here: traffic speed follows design. If towns and cities in Marin want to reduce speeds and increase safety, it must design roads that encourage people to follow the desired speed. The Golden Gate Bridge District has done the opposite, telling people to go one speed while silently encouraging them to go faster. If it’s serious about keeping speeds down, it won’t rely simply on enforcement to keep speeds down but will also seek design solutions.

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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.

5 Responses to More people are speeding on the Golden Gate Bridge – here’s why

  1. Franz Listen says:

    Good post. I think the takeaway here is even deeper than the conclusion that traffic speed follows design. It’s really about the limits of changing human behavior through engineering.

    Individuals determine their own level of risk. We can try to reduce that risk through engineering and technology but we won’t always get the expected outcomes. People can often convert the risk reduction into something else altogether. Here on the bridge, they are converting the physical improvements (risk reduction) into higher speeds. There’s a benefit to drivers, but not the one predicted.

    Something similar may happen with collision avoidance technology that is making its way into cars. On the face of it, you might expect these things to improve overall safety. However, that depends on drivers maintaining the same level of vigilance. Instead, they may simply convert the risk reduction into laziness, while keeping their same basic level of risk. The result might be easier driving (a consumer benefit), but not necessarily improved overall safety.

    This principle not only applies to risks, but to other types of costs as well. In recent decades, technological advances in efficiency and the use of lighter materials were supposed to result in much more environmentally friendly cars. However, people mainly converted that consumer benefit into the purchase of larger vehicles instead. The result has been an auto fleet with more overall capacity, but not much improved average fuel economy. Consumers have benefited, but society at large did not benefit in the way expected.

    Technology can improve our lives in countless ways, but we should be wary of predictions of the alleviation of societal challenges through engineering alone. We need to get incentives right. In public policy making we need more people thinking like economists and fewer people thinking like engineers.

  2. Alai says:

    I wonder what we have to look forward to once construction is completed on the Presidio ‘parkway’? Much higher speeds, no doubt, but to what extent will it spill out onto Lombard St.?

  3. Michael Amodeo says:

    This is actually counter to my observations the last couple weeks. I have slowed down because the lanes are narrower, with the left lane in particular feeling very tight and unsafe. I actually thought traffic control was one of their reasons to install the median.
    The post mentions an increase in accidents but the article in Marin IJ doesn’t mention accidents at all. Has caltrans released data showing that accidents have increased?
    The change that makes me feel less safe is actually the lane change that happens after the headlands/Sausalito entrance on the right and the zipper truck on the left, where two lanes open on the left (encouraging speeding in a suddenly wide open area) and the right lane merges down. This seems unnecessary and is causing confusion so far.
    Also, drivers might be less likely to speed on or near the bridge if traffic weren’t so bad elsewhere. Getting past Corte Madera feels like a jail break, and everyone rushes before hitting Doyle Drive traffic.

  4. Terry says:

    This is hardly a surprise. Over the last few decades we’ve made safety improvements on our cars but have traffic deaths gone down? As we make it safer to drive, people will naturally drive faster. All of us decide on the level of risk we are willing to take. There is only one way to deal with this problem now that the barrier is in place — enforcement. Start giving out tickets and let the public know the Highway Patrol is not going to fool around with this. If you speed, you will pay.

  5. Pingback: Today’s Headlines | Streetsblog San Francisco

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