As humans we are continually faced with questions of conscience. One such question seems utterly unique: whether to drive under the speed limit. I never follow the speed limit strictly, and I know of few people who do. I don’t even drive in terms of sixty or seventy miles an hour, but in terms of limit plus five or limit plus ten. The actual experience with most of us is that the conscience generally does not bother us about our driving speed.

We might remember the first time we told a lie or the first time we stole something from the drugstore and our mothers dragged us back and made us admit it, and we were pardoned by the spineless, kindly old manager. But who remembers the first time they broke the speed limit?

No Natural Counterpart

People’s consciences simply do not bother them about speeding in the same way they might about lying or stealing. And little wonder: the speed limit has no counterpart in the Ten Commandments or the laws of nature. There simply is nothing inherently moral about not going fast.

Regarding the laws of nature, there is one obvious example of a speed limit: the speed of light. The fastest forces in the universe, the massless particles of gravity and light, cannot travel faster than this. But this “speed limit” is not analagous to the black-and-white signs on the freeway. It’s only a “limit” because it’s impossible to travel any faster. The essential speed laws of particle physics and of natural biology are: “go as fast as you possibly can.” If we were to accept this principle as the basis for speed limits, we would be driving about with the pedal constantly floored, and our engines would wear out a lot faster.

Indeed, the notion of speed limits, in a pure physical sense, is even more nonsensical when viewed in the light of general relativity. Einstein showed that speed is relative, that acclerated motion is (for all practical purposes) indistinguishable from gravity, and that all objects are traveling through spacetime at the speed of light.

The realm of natural biology operates in a similar way. There simply aren’t any examples of creatures or processes in nature creating arbitrary, self-imposed limits on their speed.

We’ll Protect You…

What then is the thinking behind speed limits? Well, the idea is that people given an unnatural potential for destructive activity when surrounded by 2,000 pounds of moving metal. Furthermore, our reflexes (so the thinking goes) are not naturally equipped to account for and react to events at high speeds. When you have a high density of these fast-moving pinheads, you have to impose an arbitrary limit on speed, to prevent destruction to life and property. Because the natural has been sidestepped, the laws of nature, which are laxadaisical in this matter, cannot apply.

But this is exactly why we don’t feel guilty. The speed limit tells us we pose a threat, when it’s obvious to us that we don’t. Everyone’s cooking along at eighty miles an hour; what’s the problem? We may be breaking the law, but we don’t appear to be posing the threat that the speed limit says we are. On the other hand, the possibility of being late for an appointment poses a more clear and present risk, and arguably an equal claim to the dictates of conscience. So the official rules of the road are often sacrificed on the altar of punctuality or plain lack of patience.

I would argue that in most cases where a person seems to feel a moral sting while driving above the limit, it is because he or she feels a keen awareness that their behaviour poses a saftey threat, not simply because his odometer shows a higher number than the sign says is legal.

With these two things in mind — the theoretical danger posed by human nimrods hurtling around encased in two thousand pounds of metal armour, and the vast majority of everyday experience telling us it’s no big deal — we are led to ask: are speed limits really any good at mitigating danger?

What Happens in The Real World

The answer is two-part. Yes, the fact of having a speed limit at all is an effective way of preventing destruction. More on this later. But second, contrary to popular understanding, slower speed limits do not necessarily mean safer roads. This is because raising and lowering speed limits has no effect on motorists’ speeds.

“The primary conclusion of this research is that the majority of motorist on the nonlimited access rural and urban highways examined in this study did not decrease or increase their speed as a result of either lowering or raising the posted speed limit by 4, 10, or 15 mi/h (8, 16, or 24 km/h). In other words, this nationwide study confirms the results of numerous other observational studies which found that the majority or motorist do not alter their speed to conform to speed limits they perceive as unreasonable for prevailing conditions.”
— Effects of Raising & Lowering Speed Limits

“A study of speed limits on different freeway types in Michigan failed to show that speed was a substantial contributor to more frequent or more serious crashes. It showed that compliance with speed limits was not necessarily an accurate measure of safety. Although more crashes occur in urban areas, as can be expected from congestion and the need to react to other vehicles, drivers seem to choose speeds similar to the design speeds for different types of roads. The research suggests that lowering speed limits arbitrarily does not affect traffic safety. Speed limits and speed zones would be more effective if they were based on geometrics, traffic characteristics, and safety benefits rather than popular conceptions.”
— Freeway Speed Zones: Safety and Compliance Issues

In other words, common sense prevails over arbitrary law in practice.

These studies also contradict the popular idea that if you raise speed limits, everyone will simply drive that much faster and still break the limit.

The Freedom of Police Caprice

Speed limits do have value, however, precisely because of people’s current ability to fudge the system.

If there is no official system for judging safe speeds, who or what determines when safe limits have been exceeded? The answer is the whim of the law enforcement officer. Eliminating speed limits would place total authority and confidence in the universal good judgment of your local police force. We would be making the highway patrollers a law unto themselves.

Speed limit laws, however, create that higher rule of law to which everyone can look and see clearly who was right and who was wrong. They allow for the possibility of contesting the police officer’s judgment, and also allow for clear and strict punishment of drivers who actually cause accidents.

The system works because of a social quid pro quo between society and law enforcement. Drivers innately understand the need to avoid accidents, and so, on a given section of road, they will drive at generally the same speed (the design speed of the road) regardless of the limit. But patrolmen, in turn, recognize that speed limits are arbitrarily low, and do not enforce them strictly. In America, at least, most police officers generally will not pull you over unless you are going more than 10 mph above the limit — this we have (unofficially of course) from the officers themselves. But in addition, we know that if an officer is in a bad mood, he might ticket drivers for even slight overages.

Thus, the general unwritten “speed allowance,” combined with the random chance of strict enforcement, creates an environment in which we have the flexibility to use good judgment, but must also remain alert to being punished for abusing the privilege. On these grounds, I maintain that the system is not broken, and should not be changed.

The fastest way to raise speed limits would be to enforce them strictly. But as we have seen, this would not affect driving speeds, and would only call attention to a problem that arguably does not exist if you ignore it.

—JD

“What a blessing it would be if we could open and shut our ears as easily as we open and shut our eyes!”
—Georg Christoph Lichtenberg (1742–1799)