Where the streets have no signs

Eric Crampton points to an example of offsetting behaviour in driving reported by Popular Mechanics:

…modifying roads and intersections so drivers are less comfortable—by making driving, in some ways, more dangerous—forces people to slow down and pay attention, producing a change in behavior that, paradoxically, results in more safety. This is also true for pedestrians, who Vanderbilt says are more cautious away from crosswalks than within them because they don’t know if cars will actually stop.

It reminds me of the idea of shared space that’s gained some popularity, particularly in Europe. In slow traffic areas, such as city centres, streets are completely unmarked. There are not even kerbs to indicate what is road and what is pavement. The idea is that all road users will mingle and “…interact in a free and humane way, as brethren — by means of friendly gestures, nods of the head and eye contact, without the harassment of prohibitions, restrictions and warning signs.”

Apparently it’s been remarkably successful in reducing traffic speeds, diminishing the number of accidents and speeding up journeys across town. Writing that makes it sound too good to be true, so I wonder if anyone with traffic planning experience can shed further light on it? I’d be surprised if there were no risk reducing measures we could take that didn’t result in complete compensation in people’s behaviour.

9 replies
  1. Matt Nolan
    Matt Nolan says:

    On an extremely mild tangent I would note that it is not necessarily too good to be true – as we don’t know how costly it is for cars and pedestrians to have to constantly make decisions.

    In fact – if they didn’t do so before you could make the argument that the risk of dieing previously incurred a lower cost than having to consciously look out for traffic all the time. And now that people are looking out they are incurring that cost …

  2. Eric Crampton
    Eric Crampton says:

    Offsetting behaviour just means that there’s an income effect from regulation that runs counter to the substitution effect. You make safety cheaper, and people will consume more of it, except that the income effect of being safer makes them consume somewhat less. In some cases, it offsets completely, but that’s not the norm. Rather, failure to account for it makes us generally overestimate the benefits of regulation.

    Matt’s of course right that paying attention is costly and that such costs ought be factored into any proper analysis.

  3. rauparaha
    rauparaha says:

    I would note that looking at injuries and fatalities is an accepted heuristic for judging the effectiveness of traffic calming measures.

  4. Matt Nolan
    Matt Nolan says:


    Just because it is a accepted heuristic doesn’t mean that we can ignore economic logic when figuring out what is welfare maximising 😛

    The way I see it we need to actually have a reason why forcing people to incur a cost is optimal. If the agents were completely independent of each other then it would be self evident that, in the absense of individuals who are a bit silly, such a policy is not welfare maximising – even if less people die.

    However, if there is an externality we can make the argument. Namely, their is a social cost associated with people not paying attention on the road – when/if they crash they may well hurt other people. Given this specific element we could make a case for forcing agents to face an additional cost.

  5. rauparaha
    rauparaha says:

    @Matt Nolan
    Don’t forget to include the cost of the status quo. The cost of all of the traffic management devices that we install and maintain is not insignificant.

    I’m sure that the attention cost of reading the innumerable traffic signs and watching the lights all adds up, too. Lets not forget that we should all be driving defensively and watching out for pedestrians anyway. I think there’s also a benefit to our mental acuity of constantly exercising our brains 😉

  6. Matt Nolan
    Matt Nolan says:


    Definitely, definitely, include the cost of the status quo. However, given that the post was focused on the benefits of lowering the quality I thought it would be apt to include the costs 😉

    Benefit to exercising our brains – I’m pretty sure that one is internalised isn’t it 😉

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