Daggers on Steering Wheels: It's About Incentives, Baby

I'm about to start one of my "Economics for Managers(.pdf)" courses, and in an early lecture on consumer theory I explain incentives (and therefore rational-choice theory) by looking at seatbelt laws. It's a striking example, and the empirical validation is based on the work of John Adams. I've touched upon the idea previously (see e.g. this post on shock absorbant lamposts), but it's fairly self-evident that:

When driving conditions become more dangerous, we modify our behaviour and use more caution

The "seatbelt example" simply looks at this in the opposite direction, i.e.

When driving conditions become less dangerous, we modify our behaviour and use less caution

Evidently the Insurance Institute for Highway Safety is not impressed with such basic behavioural ideas, finding the suggestion that we drive more recklessly if we feel safer to be abhorent. They conclude(.pdf):

“Don’t believe them, not until they produce credible evidence that people compensate for safety”

Well, John Adams has responded:

I first produced evidence on the subject sufficiently credible to pass peer review for publication in the Society of Automotive Engineers Transactions in 1982 - “The Efficacy of Seat Belt Legislation” (PDF: 0.2MB). I have revisited the evidence that people monitor their environments for signs of safety or danger, and adjust their behaviour in response to perceived changes, in numerous publications since, including two books: Risk and Freedom: the record of road safety regulation   (1985) and Risk   (1995).

He also points out that the position is now conventional wisdom, with "shared space" becoming more and more common. Remember, if the logic behind compulsory seatbelt laws is valid, we should also encourage drink driving.

Bottom line:

If I put a dagger on your steering wheel, would you slow down?
If I removed it, would you speed up?
If you're putting in a new CD, will you wait until the road is clear, or until you're going round a bend?

Comments

[Jim]

"Remember, if the logic behind compulsory seatbelt laws is valid, we should also encourage drink driving."

Er, no. The story you link to says that having *low* levels of alcohol in your blood provides some protection from head injuries sustained. Of course, it also makes sustaining such injuries and inflicting them on others more likely. The more people drink, the more dangerous they become. The empirical evidence on this seems to be far stronger than that on seatbelts increasing reckless behaviour - if that 1982 article is the sum total of Adams's peer-reviewed work on the subject count me unconvinced.

There is some merit in the idea of reducing / removing the car user's assumption of road supremacy by turning streets into 'shared spaces', but they usually also incorporate speed limits, which I'm guessing you would oppose?

[Oli Rhys]

It does seem quite strange that many people don't understand this theory.

Having said that, maybe the problem is we all feel 'other people' only follow the rules regardless of the consequences - they are not as smart as us, and so it is in their interests that these laws exist.

However, I have only ever met a very small number of people who will travel at a legal speed regardless of conditions 'because the law says it is a safe speed'

It does make you wonder if it is time we went with what the majority thought rather than take the lowest common denominator school of thought - yet again!

[Jim]

"However, I have only ever met a very small number of people who will travel at a legal speed regardless of conditions 'because the law says it is a safe speed'"

Maybe, but there are better reasons to travel at the legal speed 'regardless of conditions'. Firstly, maybe the conditions are not what you think they are - simple over-confidence and misjudgement account for all too many accidents. Secondly, I'm sure I'm not the only one who thinks obeying the law is generally a useful social convention, and that if we each started to pick and choose which laws applied to us the roads would swiftly become much more dangerous.

As for the dagger in the steering wheel idea, wouldn't this end up killing all those people who collide with their wheels through somebody else's fault. Reckless drivers don't just kill themselves, you know. The same goes for seat-belts - even if not wearing one makes me a better driver I still might be better off keeping it on given the likelihood that someone somewhere is eventually going to drive into me.

[aje]

Jim - I'm sure the scale differs but I think the underlying logic is the same. Both are actions that increase the likelihood of crashes whilst reducing the chances of injury from crashes. Regarding speed limits, for public roads I'm in favour of strictly enforced speed limits, but don't hold that belief too fervently. Finally, the whole dagger vs. seatbelt issue is a Prisoner's Dilemma. Certainly as your speed increases so too does the importance of negative externalities.