Please Touch That Dial

Illustration by Annemieke Beemster Leverenz

I have a piece in the new issue of I.D. that considers what influence the visual displays of speedometers might have on our driving behavior. Story is here or after the jump…

Every time I drive my 2001 Volvo, I find myself staring at a design problem: the speedometer.

It’s not the placement, illumination, or typography. It’s the numbers. The maximum speed on the dial is 160 mph. I know from experience that this car, even with its turbo engine, doesn’t do anywhere near 160. It even begins to get a little wobbly around 90 mph—not that I’m at 90 very often.

So why is the maximum speed displayed more than twice the legal limit in the U.S. and almost twice what the car can handle? And what is this speedometer doing on a Volvo, a company whose heritage is predicated on safety?

Car companies actually have an ambivalent relationship with safe driving: One survey in Canada found that nearly half of all car ads depicted unsafe driving acts. I suppose that the speedometer’s high numbers are placed there to stimulate our imagination in the way that radio knobs allow us to crank up the volume far beyond the level where sound is distorted.

But even knowing that these numbers bear little relationship to reality, we’re affected by the visual display. No matter how fast we drive, the needle is always less than halfway up the dial, indicating there’s still plenty of room for acceleration. That remaining space may even goad us into testing the limits by going faster.

The speedometer presents an example of “choice architecture,” a coinage of University of Chicago professors Cass Sunstein and Richard Thaler that refers to the way context can affect behavior. In their book Nudge: Improving Decisions About Health, Wealth, and Happiness (Yale University Press, 2008), Sunstein and Thaler give the example of a school cafeteria in which administrators tried to encourage children to eat healthier food. It was found that simply by displaying the healthier stuff first on the lunch line, consumption of junk food was decreased by as much as 25 percent.

Would topping speedometers at, say, 100 mph influence the way we drive? This question was actually broached as long ago as Carter’s presidency, when the National Highway Traffic Safety Administration briefly enacted a cap of 85 mph on speedometers (with the speed limit of 55 mph marked). The measure was done for energy savings, not safety, but it was undone by the anti-regulatory Reagan Administration—one of whose first acts was to remove the solar panels that had been placed atop the White House.

Capping the speedometer would remove a theoretical and illegal max to test on public roads. Influenced by the so-called anchoring effect, people are induced to eat more when portion sizes are larger and to drink more when the range of beverage options is increased. (Many consumers eschew the biggest and smallest drink choices at fast-food restaurants, so companies have supersized their “large” choice, thus making the “medium” more palatable, even though it’s bigger than ever.) In the same way, the value of 160 on my speedometer has been shown to influence decision-making.

Even more troubling is the speedometer’s dumbness. The device gives a simple reading that lacks context. It tells speed, but it doesn’t convey other useful information. How does the car’s speed compare to the posted limit? How much time is saved by driving faster, and how does it compare to the added fatality risk of a crash (which rises exponentially at higher speeds)? What’s the minimum stopping distance at a certain speed? What is the fuel consumption (expressed in dollars per hour or some such) and rate of harmful emissions at one speed versus another? As the Prius’s dashboard monitor displaying fuel efficiency shows, when people receive live feedback about the consequences of their actions, they are more likely to change their behavior.

Stanford University researchers Manu Kumar and Taemie Kim have proposed a “dynamic speedometer” that would highlight the posted speed limit of whatever road you’re on. In simulator trials, they were able to reduce instances of unintentional speeding and convince subjects to drive more slowly in general. By adding the information previously mentioned, people might be “nudged” to make smarter decisions about their driving. For now, most don’t have a clue.

Tom Vanderbilt, a contributing editor at I.D., is the author of Traffic: Why We Drive the Way We Do (And What It Says About Us) (Alfred A. Knopf, 2008).

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This entry was posted on Saturday, October 18th, 2008 at 2:12 pm and is filed under Uncategorized. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

9 Responses to “Please Touch That Dial”

  1. Pete W Says:

    A dynamic speedometer is an interesting idea, but drivers I know would probably still increase their speed by 5-10 mph.

    I like the idea of a stopping distance meter a lot.

  2. Colin Says:

    Some time ago I wondered about the possibility of a scheme where RFID tags inserted in the kerbs broadcast the speed limit, and car speedometers would receive it, indicate it on the speedometer, and perhaps colour the whole instrument dash in red if the speed of the car exceeded it.

    Or more intrusively, sound an alarm if you exceeded it. Or delivered an electric shock through the steering wheel. Anything’s possible.

  3. gecko Says:

    Some Ferraris from the late 70s/early 80s had the standard speedometers, but they just blacked out the numbers and markings above 85. There would just be a big black or red stripe on that section of the arc.

  4. mdf Says:

    Just a few minutes ago, with flashlight in hand, I just went outside to check a few parked cars “at random” … and it turned out I was right: the 100km/h indication is at, or very close to, the 12 o’clock position on the dial.

    This is probably not a coincidence, and would explain why even SUV’s get “180km/h” (or more) on the dial. But why 100km/h at 12? My guess is some kind of car-to-car commonality, like turn signals, which pedals are the accelerator and brake, and so on.

    Basically, standardization.

    Has anyone gathered any data re: speeding tendencies that included analog vs. digital speedometers?

    As for smarter instrument displays:

    Various car navigation systems will start making noises if you are going faster than what it thinks is legal (my TomTom does).

    You can also purchase things like the ScanGuageII which will in fact display “dollars per hour” and similar fuel consumption statistics. Interesting thing about my ScanGuage is this: I installed mine right on the top of the dash, directly above the original speedometer. I configured it to display the speed … and ever since I hardly ever look at the real speedometer any more.

    I think the coming age of super-efficient cars will give car manufacturers a long overdue chance to re-arrange or re-design, the interior instrumentation — maybe even allow configurability. My favorite example of this is the Aptera Typ-1e (“Local”): but for some climate control knobs, it is a pure glass cockpit. Even the rear view mirrors are video displays, an idea which I hope catches on since it would essentially solve the blind spot problem, as well offer the driver the absolute minimum check times.

    The GM Volt is (sadly) less radical.

  5. Jean Vincent Says:

    I like the ideas of the cost meter, and danger meter.

    The cost meter could be in dollars per mile or in miles per dollar. Which one would be best from a psychological standpoint?

    The danger meter is more difficult to implement because it needs a smart-road system providing real-time feedback to the car consistent with actual driving conditions (wetness, oiliness, iciness, fatigue, visibility, measured driver reflexes, other vehicles speed ahead). It could be displayed as a color scale, such as Green, Orange, Red. Red meaning danger of course, Green meaning safety, and Orange meaning warning.

    We could then tie this to an automatic speed control system that would automatically accelerate and decelerate slowly to keep us at the limit between the green and orange zones, exceptionally the system could brake if suddenly the danger would reach the red zone.

    With a danger-meter we could remove the speedometer if the speed limit was dynamically implemented by such a smart system. It would be illegal to be in the red zone and recommended to stay in the green zone.

    This should be complemented by an estimated time of arrival system that would remove the stress associated by not knowing one’s speed.

  6. Chris Says:

    So it isn’t our fault how we drive?………… Maybe it is designed this way to make it look bigger and better then it really is. Isn’t that what corporate design is all about? I do agree that “most don’t have a clue”, but by changing the numbers on the dash (that they probably don’t even look at anyways) will not give them that clue.

  7. Mike Chalkley Says:

    @Jean Vincent – wouldn’t a ‘danger meter’ prove to have the same effects that current signage & road building does by implying that some parts of our journey are a lot safer (as in Tom’s book Traffic where he argues for shared space) and thus actually prove more dangerous? Unless it was completely self-referential in which case it would always say ‘max danger’! ;)

    I drive a BMW 530 (which with UK fuel taxes means Petrol is my major consideration in terms of driving costs) which has a real-time MPG meter. It scared the crap out of me when I first got the car but now I never even notice it. I have accepted the relatively high cost of driving it as a consequence of having a really nice car to drive. I suspect any such feedback to a driver will eventually fade.



  8. Ed Heath Says:

    I purchased a device called a ScanGauge II that gives you real time information about your fuel economy and much more (which I don’t use). It plugs into the OBD port, and definately influences my driving. It runs around $160, so it is not likely to pay for itself (with my limited driving), but I still appreciate the MPG information. It is somewhat distracting, but since I am driving reasonably more conservatively now (at least some of the time), it seems to balance out.

  9. Bob Davis Says:

    My current “daily driver” is a 2001 Honda Accord that does have the speedometer that reads up to 140 mph. It also has kM for our Canadian friends/amis. My previous car was a 1988 Dodge Aries, and (as I recall) it only went to 85. Ironically, this the car I had when I received my only speeding ticket in the last 30 years–doing 70 in a 55 zone on I-5 in San Diego County. An earlier rig was a 1960 Ford pickup; it also read up to 80, but around 60, “the pistons started a-swappin’ holes” and 55 was its practical upper limit. And, yes, I think anything over 90 is a waste of numbers.

    I come from a railroading background, and there we have “restricted speed”, which means a speed in congested areas or work zones where a train is kept as a speed that allows a safe stop “short of any obstruction”. For drivers it should apply when passing areas where workers may be getting out of trucks, or where there’s foot traffic, or any place where one might need to stop quickly.

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Traffic Tom Vanderbilt

How We Drive is the companion blog to Tom Vanderbilt’s New York Times bestselling book, Traffic: Why We Drive the Way We Do (and What It Says About Us), published by Alfred A. Knopf in the U.S. and Canada, Penguin in the U.K, and in languages other than English by a number of other fine publishers worldwide.

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