How Dangerous is Exceeding the Posted Limit?

I’ve often felt that the emphasis on speeding is misplaced. It’s easy to see how it might happen, it’s probably the most visible and the most common traffic violation we all witness. The government and industry sponsored groups like the IIHS have also done a fine job of scaring us into believing statements such as “speed kills” so much so that there is a misconception about how dangerous it really is. Using this data from 2005 from the CDC, I wanted to put into perspective just how prevalent exceeding the posted limit is as a cause of death in the United States. Be careful, I’ve made an important distinction here. ‘Speeding’ is loosely defined as driving too fast for conditions or exceeding the posted limit. It’s important to distinguish ‘exceeding the posted limit’ from ‘too fast for conditions’ because photo enforcement can only detect ‘exceeding the posted limit’ violations. An example of ‘speeding’ could be driving the speed limit during pouring rain or driving on an icy road at 10mph below the posted limit. Cameras cannot identify these situations and make that judgment call. The CDC report does not separate causes of death due to exceeding posted limit. For that, I referred to the 2008 NHTSA Accident Causation Survey which concluded that less than 5% of all crashes were caused by exceeding the posted limit. For those of you still doubting this government agency’s numbers, reference the Governor’s Traffic Safety Advisory Council 2009 Fact sheet which states that 80% of all crashes occur below the posted speed limit. It also says that speeding (above posted limit or not) contributed to 1/3 of all fatalities. Doing the math (1/3 x 20%) we arrive at an estimate of 6.66% of all fatalities caused by exceeding the posted limit. This is the figure used in the chart and is an estimate only. Even if you double the figure, the conclusions are still the same. In the NHTSA report, the total fatality rate for all crashes of all causes was less than 1%. Annually, only about 0.1% of all deaths in the US are caused by exceeding the posted limit.

Causes of Death in the United States

Causes of Death in the United States

Another Perspective


Let’s look at it from another perspective. In 2005, there were 2.966 TRILLION vehicle miles driven in the United States (according to the Federal Highway Administration), and we figure only 3023 deaths caused by exceeding the posted limit. This is almost one death per BILLION miles driven. The odds of winning the lottery are better!

Let’s take it a step further. I’ll assume that 20% of all miles driven are driven above the posted limit. Statistically speaking a person would have to drive almost 200 million miles before being “due” for a fatal auto crash due to exceeding the posted limit. If you think the number is closer to 40%, then you still have to drive almost 100 million miles in order to be involved in a fatal accident due to exceeding the posted limit!

I’m not going to go into figures, but it’s also widely published that more auto crash fatalities occur on rural roads than urban roads and interstate highways. Yet for some reason, cameras are typically only found in urban areas and well-traveled roads. Revenue, or safety?

Now with proper perspective on the big picture of all causes of death in the US, you can see why the focus on speed enforcement is misplaced. Driving on our roads is safe! More than six times more people die of poisoning and falling than in auto crashes caused by exceeding the posted limit! If we really wanted to save lives, there are clearly better areas to focus on.

Realistic Goals


One other aspect of the illegitimacy of photo enforcement is an unclear program goal. Are we trying to squeeze blood from a turnip? It’s unclear just how much improvement can legitimately be achieved by stepping up enforcement of speed limits. Even if photo enforcement was effective at reducing fatalities caused by exceeding the posted limit, what’s the best result we could expect? A 10% improvement? Maybe 20%? You can’t put cameras everywhere. A 10% improvement would save only 300 lives per year. This isn’t to say that 300 lives aren’t valuable, but in the whole scheme of things, if you want to save lives, there are over 2.4M other lives to be saved from other causes of death that may be easier to achieve if we focus our efforts more intelligently. It would be a lot easier to save 300 more lives from suicide or poisoning than from drivers exceeding the posted limit. Clearly, speed cameras are about REVENUE, and not safety, and there are better safety areas for us to focus on than speed limits. And engineering improvements that achieve speed limit compliance naturally and have lasting effectiveness can probably have a much more dramatic effect on road safety than anything else.

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3 Comments

  1. cjwagner
    Posted June 11, 2009 at 2:24 pm | Permalink

    “You can’t put cameras everywhere”

    sure, give them a challenge….

  2. Posted June 11, 2009 at 3:41 pm | Permalink

    Government entities, especially local ones, are *not* filled with people interested in the safety of drivers on the roads (owned by the government, since private roads have been made virtually financially impossible by governments in most locales). If they were they would utilize actual technological methods in the construction of highways that have some effect towards reducing the incidents of accidents on them. Just one example is a step up from the grating on the road edges, now often incorporated in resurfacing, which creates a rumbling sound when the vehicle tires run over them thus warning the driver – Road Talker, an actual audio message. http://mb-soft.com/public/roadtalk.html I am sure that civil engineers designing highways have other features in their designs besides banked curves that allow a car with good handling and well tred tires to travel them far beyond the government decreed “speed limit”.

    Good comments. While photo enforcement is not a partisan issue, it’s my observation that republicans generally believe in the self-sufficiency of the population and that people can take care of themselves and make their own decisions, while it is the democrats that believe we are all helpless sheep and need the government to take care of us and dictate how we live our lives so that we remain “safe.” –admin

    Your conclusion that governments use “speed cameras are about REVENUE, and not safety” is a logical one and one I reached some time ago. I would add that revenue is a major factor for traffic law enforcement as a whole – where is the “safety” factor when an agent stops someone for a rolling stop or exceeding the “speed limit” when traffic is very light (not referring to someone zipping in and around slower cars) or even on empty roads?

    I will add that another factor exists – that government officials consider the general populace too stupid to make smart decisions and therefore require treatment as though they are all significantly mentally deficient. If governments were really interested in having a populace where interactions between individuals are orderly – and sharing a driving surface is a type of interaction – they would have measures in place that encourage self-responsibility. Each individual properly should be held responsible for the physical harm that s/he causes another instead of the “share the blame and responsibility” culture that has predominated in the US since at least the past 40 years. (I recall none of this attitude when I was a teenager in the early 60s.)

    The underlying premises that individuals in society need to be treated as mentally deficient (and therefore incapable of learning by experience and self-responsibility) *and* that without government there would be chaos are widely promoted indirectly by government. However when even moderately examined, both of these ideas are shown to be blatantly false. In the meantime, fines are another way to steal money from the populace.

    • Ev Mecham
      Posted June 25, 2009 at 12:41 pm | Permalink

      so what she is saying is…. its ok to break the traffic laws as long as traffic is light? so it is ok to murder someone who has no family left on this earth? as in nobody would miss him/her?

      laws are not made to be broken as long as no harm comes to anybody.. it is the behavior of citizens that laws are made to change and the fines are to there as a deterent for those thinking of breaking a law and to punish those that do break the laws.. if no punishment was ever handed out there would be no reason to abide by the laws !!!

      so we can assume the admin is a republican ! great ..just great.


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