Fact-Checking the Toyota Hearing: Lower Speeds Increase Safety

Megan McArdle at the Atlantic, writing on today’s Toyota hearing in the House oversight committee, hears Transportation Secretary Ray LaHood claim that "lowering the speed limit to 30 mph would not save any lives, which is why we have minimum speeds on highways."

lahood.jpgLaHood, at left, with the president at right. (Photo: whitehouse via Flickr)

Leaving aside the gaping logical hole in that statement — which Robert Mackey of the New York Times suggests (check out the 12:04 post here) may have come from Souder’s argument that lower speed limits would save more lives than "100% safe" cars — there is plenty of research out there pointing to the beneficial effects of lower speeds on safety.

Traffic author Tom Vanderbilt recently cited the impact of 20 mile-per-hour urban speed zones on reducing road injuries in the United Kingdom, and a 2007 study by the AAA Foundation for Traffic Safety [PDF] outlined the following "general rule of thumb":

When travel speed increases by 1%, the injury crash rate increases by about 2%, the serious injury crash rate increases by about 3%, and the fatal crash rate increases by about 4%. The same relation holds in reverse: a 1% decrease in travel speed reduces injury crashes by about 2%, serious injury crashes by about 3%, and fatal crashes by about 4%.

Could LaHood be unaware of the relationship between lower speeds and decreased risk of injury? It’s certainly possible — despite the former GOP lawmaker’s good record on infrastructure reform and sustainability, both in concept and in practice, he remains a relative newcomer to the nitty-gritty of transportation, as the Times reminded readers in a highly readable profile last year.

  • Zufechten

    I’m sure the Secretary is aware of the relationship between safety and speed. What is less clear is the relationship between speed limits and speed. Absent enforcement or road features that encourage lower speeds, changing the number on a sign does not seem to have a large effect on how fast people actually drive.

    Since it has worked with seat belts, a combination of enforcement and public information campaigns may have the best chances of working short of turning every street into a woonerf.

  • Let us not forget that fully 40%+ of our traffic is commercial folks. You know, people stocking our shelves. What would the impact upon the price-index be in this fantasy scenario? How would you reconcile the safety argument then if a double-standard is deployed.

    Please, continue and don’t let a little thing like my personal-liberty stand in your way. I WANT to spend my entire life transporting myself instead of living. Who doesn’t!

  • Reducing speed – designing roads for lower operating speeds – has a very real impact on pedestrian fatalities. 80% of pedestrians struck by a car going 40 mph will die. If the car goes 10mph slower, the likelihood of pedestrian death is halved to 40%. At 20 mph, the fatality rate is just 5%.

    There’s also the needed paradigm shift to active safety from passive safety (for example: trees slow drivers, keeps them safe; removing trees keeps drivers from hitting them when they veer off the road).

  • Henry

    States that raised speed limits higher to 70 mph or higher experienced a larger drop in their fatality rates than states keeping 65 mph speed limits on rural interstate highways between 1994 and 2003.

    Lower speed limits do not save lives.

  • Stephen

    Oh give me a break. 15 after the end of the 55 (will a lot less deaths) and we still have to argue with people who believe that going slower will somehow translate to safer roads.

    IT WON’T.

    We should not be basing speed limits on “what happens if you get into a crash”. If we did that than we should ban all air travel since the approach speeds are almost as fast as NASCAR!

    WE need to ask the question. Can most drivers drive safely faster.

    The answer is YES,

    AS for the pedestrian fatalities, it is interesting to not that MOST ARE THE FAULT OF THE PEDESTRIAN WALKING INTO TRAFFIC. No amount of “it must be the drivers fault” is going to change that.


    Set speed limits at 85% speeds, the safest way to set a speed limit!

  • Wikipedian protestor


    {Citation needed}

  • Tim

    Typical Washington…Let’s see….how can we brainwash more Americans…Let’s get back to the speed limit game that we shoved down their throats for some 24 years with the 55 saves lives campaign….just like global warming, most will be scared into believing this crap because they’re afraid for their very lives! Give it a break already…most people drive between 70-80 no matter what the sign says. Here in western NY the thruway speed limits are set at 65 and 55 when a lot of areas, but traffic flows mostly around 70 regardless. So why not set the limit at 70-75 to make it safer? Of course that would take away revenue and probably by putting a realistic number on a sign it would kill us all!!!

  • Gerrit

    Speed limits won’t make a difference until they are followed. It seems to be a rule in my area to drive at least 35 mph although signs try to limit speeds to 25 mph. With everybody driving faster I found it hard to stick to limits myself because it makes you an obstacle to others and quickly trigger some road rage. I think the biggest problem is the general degree of inconsiderateness for others. Everybody cares only about themselves and their own speed and comfort. Pedestrians, cyclists, buses, slower traffic user are often subject to aggression and anger. The only thing that may forward a change is a combination of education, law enforcement, and physical elements like speed bumps. 1) If you make it more difficult and more expensive to get a driver’s license, people will be more careful to ensure they will keep it for a long time. 2) If traffic violations lead to fines, legal trouble and even loss of licenses, a lot of people may change their minds about driving a race while talking on their cell-phones. 3) If driving fast damages their expensive cars, they will treat speed-bumps very carefully.

    Blame games on who is supposed to be on the roads and who’s not, who’s at fault, pedestrians or cyclists don’t lead to any solutions. It always takes two to cause an accident. It doesn’t matter who didn’t pay attention. If a pedestrian hasn’t paid enough attention crossing the street, it was also the driver who hasn’t paid enough attention to the many variables and exceptions that could occur during his journey. It could be kids running on the street, or some elderly who don’t make it fast enough, it could be an insecure cyclist who occupies more space than a pro, it could be a drunken car driver, or somebody who looked after the other sex rather than paying attention to the road. There are countless scenarios that could lead to an accident. It’s up to the driver, pedestrian, cyclist, whoever uses the roads to always be alert and aware of it and behave accordingly. Many people tend to forget that in the safety of their warm and airbagged cars. If I hadn’t paid attention to other people’s misbehavior I could have had many accidents in the past few years.

  • Zufechten

    Any argument from interstates and freeways is irrelevant to Streetsblog. Interstates are not streets, and interstate speeds are not appropriate to streets.

  • dylan

    speed are safest at 85th % speeds which is about 85mph


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