Wednesday, July 19, 2006

Gazette: "Is Faster Safer?"

The Gazette has an editorial this morning (July 19) about highway speeds that got me thinking about a number of things -- other than speed limits. Editorial, "Is Faster Safer?" The Gazette, July 19, 2006.

1. Because it seems (to me) intuitive that higher speeds would correlate with more accidents, I've kind of bought into that assertion without questioning it. (As I mostly walk and bike, and only put about 500 miles a year on my vehicle, none of this affects me very much personally -- either the danger or the desire to drive faster.)

On the assumption their numbers are right, the Gazette's editorial offers some interesting perspectives on my "intuitive conclusion":

"Alcohol was involved in nearly 40 percent of fatal accidents in 2005, and 56 percent of those killed in vehicle accidents were not wearing seat belts. . . . 80 percent of accidents (fatal and non-fatal) involved a driver who was drowsy, using a cell phone, applying makeup, distracted by children or otherwise not fully concentrating on the job at hand."

2. I don't cite this (for now) to argue one way or another about the impact of speed limits on accidents, but rather to raise some issues about arguing about the impact of speed.

There would be very little public policy discussion throughout the day if we had to have readily at hand all the relevant most current data and the sources from which it was obtained. We cannot do thorough research prior to every occasion we are about to engage someone in discussion of an issue.

But it is perhaps useful, for those interested in maintaining civility of discourse (and, in the process, friendships as well) to be mindful of the possibility that there are relevant data of which we are unaware -- such as the facts the Gazette brought to my attention this morning.

We need to ask ourselves, as well as those with whom we are talking, what general semanticists consider two very basic questions: "What do you mean?" and "How do you know?" We need to recognize that what produces the language we use is an electro-chemical process inside our skull -- not something outside. We need to more often utilize qualifiers, such as: "to me," "I'm not familiar with the research or data, but intuitively one would think," "I'm basing my opinion on one anecdotal experience I had; I know that's not statistically significant," "there may be a lot of facts here of which I am unaware, but . . .," etc.

I'm reminded of a comment attributed to Aristotle. A group of men were debating how many teeth a horse has. The debate was growing quite hot. Aristotle brought it to a halt with the suggestion, "Why don't we go find a horse and count them?" One of my favorite former school superintendents had a large sign on his wall, "In God we trust . . . all others please bring data." (I think Aristotle gave it to him.)

3. To return but briefly to the presentation in the editorial, are the statistics it cites dispositive of the issue? I don't think so (nor did the editorial writer). The answer (to whether we should have increased speed limits) does not require a choice between "inattentiveness" or "speed."

(a) There will probably always be a proportion of drivers who are drunk, not wearing seat belts, or inattentive while driving. Isn't the issue then whether they have more (and more serious) accidents at 75-80 mph than at 55-60 -- not whether "the cause" of the accident was "speed or inattentiveness"?

(b) Similarly, even sober, belted, and attentive professional drivers (e.g., NASCAR and semi-truck drivers) have accidents. There can be mechanical failures, or unforeseeable hazards created by others. The time and distance it takes to stop a moving object is in part a function of speed. Again, the researchable question might be whether even these skilled drivers have more, and more serious, accidents as their speed increases.

(c) There are at least two questions here. (1) Are there more accidents at higher speed (regardless of the skill of the driver)? And (2) Are there more serious accidents at higher speed (regardless of the skill of the driver)? The first is the issue the editorial addresses. On the second, intuitively and without data, I would think principles of physics would suggest that the higher the speed the greater the force of the impact and, therefore, probably the greater the potential damage to vehicle and driver.

4. Finally, the Gazette's added data raises a more general observation. Many -- possibly most -- of the problems any individual confronts are problems of their own making.

Consider health. How much could one improve an individual's -- or a nation's -- health if we'd follow the apparently well-documented suggestions provided us by every source from our mothers to the daily newspapers: regular exercise, weight control, proper nutrition, adequate sleep, lots of water, elimination of tobacco, minimal amounts of alcohol, treatment of addictive behaviors -- including the suggestions from the Gazette's data regarding driving (don't drive drunk, wear a seatbelt, be attentive to driving)?

(Indeed, reliance on medical treatments can be a part of the problem. It even has a name: "iatrogenic disease" -- medical conditions brought on by a doctor's treatment or a hospital stay. One study -- I believe of a hospital in Boston -- concluded that 30% of the patients there were suffering from iatrogenic disease.

My doctor says that about half the time (but note, not always) you'll recover from most conditions without any medical treatment at all. If roughly one-third of the time you to go to a hospital you'll end up worse, with some iatrogenic disease in addition to your original condition, my math suggests you have only one chance in six that medical treatment is actually going to make you better.

This is just one more reason to keep yourself healthy and avoid the need for medical treatment.)

How many financial problems, regardless of income -- and up to and including bankruptcy -- could be prevented (or at least reduced) by using some very basic tools of accounting, controlling impulse buying, and reading Consumer Reports?

Walt Kelly's Pogo had it right: "We have found the enemy, and he is us."


John Neff said...

Collision Pysics

A useful fact 60 mph = 88 feet per second.

The collision energy is proportion to the mass of the moving body times the speed squared. One can calculate how far one have to fall to have the same energy per unit mass as a collision.

Speed,Dist. traveled in 0.1 sec., fall distance.
15 mph 2.2 ft 16.7 ft
30 mph 4.4 ft 66.4 ft
60 mph 8.8 ft 240.8 ft
75 mph 11.1 ft 376.3 ft
90 mph 13.2 ft 542.0 ft

If you fell in air your terminal velocity would be about 50 mph which
limits the damage (but not enough to matter).

Teenagers have very fast reaction times and think they can avoid the consequenses of doing something dumb while driving.

Nick said...

Useful info. Thanks.

But if you'll pardon the line, I guess the moral of this story is that if you ever find yourself in a car that is travelling vertically rather than horizontally you best have your air brakes in good working order.

John Neff said...

The distances one would have to fall to have the same energy as a horizontal collison need to be divided by 2.0.
the correct values are;
15 mph 8.5 ft
30 mph 33.2 ft
60 mph 120.4 ft
75 mph 188.2 ft
90 mph 271.0 ft

Would you like to be held 8.5 ft above the ground and then dropped?

sajohnson said...

A couple thoughts on the issue of speed limits:

1) It is of course obvious that, all else being equal, a car slamming into a brick wall at 100 mph will suffer more damage than an identical vehicle hitting that wall at 50 mph.

Slower is safer. Not driving at all is even more safe. Never leaving one's house is safer yet.

Why not lower the speed limits on Interstates to 45 mph -- or even 35?

My point of course is that life is full of compromises. When it comes to setting speed limits, civil engineers use something called the 85th percentile speed. That is the speed which 85% of drivers would travel at or below -- given good conditions and no threat of law enforcement. Because most folks have a fairly strong self-preservation instinct, this typically ends up being a reasonable limit -- safe and efficient.

Unfortunately, our state legislators often completely disregard established civil engineering practice and set speed limits at the 20th, 30th, or 40th percentile speed, effectively making criminals out of the vast majority of drivers -- particularly on Interstate highways. A cynical person might come to the conclusion that their motivation isn't safety, but 'revenue enhancement'. In addition to the state treasury, insurance companies benefit tremendously because they can charge higher premiums to drivers with speeding violations -- even if those drivers have _never_ had an accident in 30 or 40 years. [Shouldn't actual accident claims be the primary factor determining premiums?]

2) That said, there really is no limit that is appropriate under all conditions. A highway posted at 65 or 75 mph might become incredibly dangerous at that speed under adverse weather conditions. I believe Montana (and Iowa, years ago) had the right idea with their "Reasonable and Prudent" speed limits on Interstates and other limited-access highways. Instead of treating drivers like irresponsible children, they allowed them to decide what was a reasonable speed considering the weather, traffic, the condition of their vehicle, etc. The problem of course was that revenue enhancement suffered. An arbitrary number on a road sign is objective -- "Reasonable and prudent" is subjective and therefore it became hard to convict drivers of "speeding". Drivers were ticketed for traveling at 105 or 110 mph on a deserted arrow-straight multi-lane Interstate and were able to get the ticket thrown out by a judge who was not convinced that _under those conditions_ 110 mph was unsafe.

As I recall, traffic fatalities remained about the same before, during, and after Montana had their "Reasonable and Prudent" speed limit.

Germany has _no_ speed limit on sections of their Autobahn and (the last time I saw the stats) their fatality rate was no higher than ours. Of course, it is much more difficult to get a license in Germany, they are very strict when it comes to DWI, and where there are posted limits they are enforced -- no 10 to 15 mph 'cushion'. We could learn a few things from them.

3) We often hear people say, "If the speed limit is raised, people will continue to drive 10 or 15 mph over the limit". That may be true -- but only up to the point where the limit is reasonable. By definition, if the limit were set at the 90th percentile speed only 10% of motorists would exceed the limit. The main reason people exceed the speed limit now (particularly on Interstates) is that it is set ridiculously low (again, under ideal conditions).

University and government studies have shown that in actuality, most people drive at a speed they consider safe and comfortable -- that raising or lowering the speed limit by 10 or 15 mph has very little effect on average speeds. Typically the traffic speeds only vary by approximately +/- 1.5 mph.

4) Here in Maryland, my observation is that the state, county, and local police officers _routinely_ exceed the posted limit by at least 20 mph. I've lost count of the number of times I've been going about 20 mph over and had a cop blow by me doing close to, if not over 100mph. No lights, no siren, just cruising down the highway. If traffic is light and conditions are good I don't have any problem with that -- as long as they don't go into flaming hypocrite mode and start giving tickets to people driving slower than they do.

My point is, if even the _police_ are flagrantly violating the law on a regular basis -- shouldn't we at least consider paying attention to the recommendations of our civil engineers?

5) I thought the following observation was a good one:

"(a) There will probably always be a proportion of drivers who are drunk, not wearing seat belts, or inattentive while driving. Isn't the issue then whether they have more (and more serious) accidents at 75-80 mph than at 55-60 -- not whether "the cause" of the accident was "speed or inattentiveness"?"

That is certainly true. I would suggest that instead of having our laws influenced by the 'lowest common denominator' we get the drunks and inattentive drivers off the road.

It's past time that the US get serious about driver licensing. There are simply too many cars on the road in many areas of the country. Our population keeps increasing and our infrastructure is being overwhelmed. Many states cannot even maintain their existing roads, let alone build new ones. If a person can't drive without talking on a cell phone, reading a newspaper, eating, drinking, applying make-up, shaving, changing clothes, using a laptop computer and/or turning around to talk to kids in the back seat, then they should not be driving -- period. A car is not a bathroom/office/home theater/kitchen.

Those of us who take driving seriously should not be forced to drive at mind-numbingly slow speeds because Britney needs to talk on the cell phone and fix her make-up while behind the wheel or because Jim-Bob needs to eat his Big Mac and wash it down with a couple beers while cleaning his deer rifle as he's cruising down the road in his Ford F-150.

Enforcing _reasonable_ speed limits is fine, but the police need to pay a bit more attention to 'inattentive (aka negligent) drivers.

6) I also agree with the following:

"There would be very little public policy discussion throughout the day if we had to have readily at hand all the relevant most current data and the sources from which it was obtained. We cannot do thorough research prior to every occasion we are about to engage someone in discussion of an issue."

With that in mind, for more information, studies, and stats go to They are an advocacy group, and therefore biased, but they do cite studies done by (presumably) unbiased organizations and provide a good balance to the typical hand-wringing and spin from the usual government and insurance industry groups that the mass media cite.

I should also note that I do _not_ agree with all (or even most) of the NMA's positions, but they are a good source of information and/or another viewpoint.