Negligent Design or Negligent Driving?

Via the St. Petersburg Times comes an interesting discussion of highway design featuring an old bugaboo, exiting on the left. In Traffic I spoke with some people at the FHWA who mentioned, essentially, that contemporary highway design tries to avoid exiting on the left, for a variety of reasons, including driver expectancy.

The piece brings up a number of issues. For one, it notes that three people have died on this section of highway, including one last week. No figures are given before that, though the facility opened in 1978. So whether this is an epidemic, or merely random, is hard to say; there may be a “regression to the mean” and we won’t see any further fatalities for the next ten years.

Second, and always lurking, is the issue of “driver behavior.” The most recent fatality, the article notes, was traveling 93 MPH. Is there a social responsibility for protecting someone behaving that negligently? If he had died by striking another vehicle, we wouldn’t be talking about bad design. Further, can good design save everybody (and what would the cost be)? I’d say we should be more worried, socially, about the harm that person may cause to others (and keeping those people off the road). The German autobahn was and is considered a design marvel; its smooth tarmac has also been home to many spectacular deaths.

The piece notes: “The left exit is counterintuitive, forcing drivers to slow down in the fast lane. The road’s elevation occludes a clear view of what lies around the corner. And the short, angled barrier walls do little to keep vehicles on the road, he said.”

Well, technically, people, there’s no such thing as a “fast lane.” There’s a passing lane. There’s also a speed limit. I also note a sign that clearly marks a reduction in speed on the ramp. And this isn’t really the sort of left-hand exit that people normally talk about giving drivers’ trouble — this is really the majority of the highway quite clearly swooping up and off to the left.

That said, the state engineers may be a bit too blithe in dismissing the risk. As a casual observer, I can imagine any number of small tweaks that could be done here relatively cheaply (cheaper than raising the height of the concrete walls). Rumble strips, flashing lights on the signs, etc. But I wouldn’t say this warrants some expensive overhaul — where’s the money coming from, anyway? — due to the actions of some severely negligent drivers.

(Horn honk to Shirl)

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This entry was posted on Friday, March 6th, 2009 at 11:39 am and is filed under Traffic Engineering, Traffic safety. 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.

5 Responses to “Negligent Design or Negligent Driving?”

  1. Christopher Monnier Says:

    If the design affords fast driving, then it should also include whatever safety mitigation is necessary for the level of driving afforded by the road.

  2. dance Says:

    I tend to speed, and I find that the “Limit 65 / Your Speed 72″ signs REALLY work.

    Also, I-5 through the mountains from OR to CA has little graphic signs of trucks falling over going around a curve, and those totally make me slow down.

    Re the design—I remember when I was a kid, and the limit was 55mph in the 70s-80s, and my mom would always say “these roads were built (designed and banked) for 70-75mph.” But now the limit is 65-70 in a lot of places, and people are going 80-90mph, and were the interstates built for 90mph?

  3. Monk Says:

    Up until last summer, that stretch of highway used to be part of my daily commute. I think there are two factors here that make it worse than it might be.
    One is that it’s actually two left exits in a row. As the first picture shows, you start with four lanes. The leftmost exits, and the second-to-the-left splits into the exit and to continue down the road. About a quarter-mile down, that lane exits, and the next one over splits. So you are left with two lanes, but immediately after this, it merges with an on-ramp from the left, and the rightmost lane ends. So for through traffic, the best place to start is the second-from-the-right. If you know this ahead of time, great. From experience, less than half the people do, usually.

    The second factor is that, from the vantage point of the top picture, there is an on-ramp on the right, right behind the “camera.” And it’s a very convenient way to get across town to get on the highway and cut across all the lanes of traffic to get onto the first exit.

    Oh, and there’s a Major League Baseball stadium between the two exits. Many of the accidents happen on game nights.

    I’d also like to mention that the “too low” barriers are the only thing on the Sunshine Skyway bridge between the cars and the water, not too far south of these exits.

  4. Chick Whitten Says:

    Bonjour! I am writing this from La France Profond, in Gascony, SW France. We have very good autoroutes, mainly “turnpikes”, or toll roads, which help to pay for improvements in the system: or so we are told. We don’t pay a road tax, or have to pay for a new licence plate every two years. The revenue comes from the tolls. Dodging any form of tax is a national sport here. What has provoked me to post this is the fact you can exit on the right! I’ve been driving for 52 years and have driven through 32 of your States, plus Canada, so I feel qualified to say, that is effing dangerous! We don’t stay in lane and have passing either side. We use the outside lane for passing, and as we mostly have 2 lanes, we return to the right. Three or four lanes only around cities. Actually very similar to the States, as I remember. The difference being our speed limits are 81mph dry, 70 wet and 56 on ordinary main roads. I often drive to England and the 700miles of autoroute I cover in 10 hours usually, there is nowhere you can exit on the left. It does not work. There are more than enough deaths already on our roads. Bonne journee.

  5. Chick Whitten Says:

    I can not seem to edit my text on this site! I meant to say…EXIT ON THE LEFT! Merde, the whole point of my text.

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