Keep Right Except to Pass

I've never had the pleasure of driving on the German Autobahn. But I've been told that traffic there flows smoothly. Drivers keep right except to pass. No one passes on the right, because there is no need. It is severely frowned upon. In fact, passing on the right may prompt another motorist to contact law enforcement, with the result that you get pulled over. I don't know if that's really true, but I like the idea that rules of the road are understood and followed.

It's different here. The slower drivers seem to spread themselves out among all available lanes, as if there is some vast, middle-of-the-road conspiracy to slow everyone else down. Somehow they have never learned the rule that slower traffic should keep right. Or that passing should be done on the left. Or that passing on the right violates convention and is thereby less safe.

I believe this is part of a general lack of understanding of speed on the highways. Many of us are quite familiar with the expression, "Speed Kills." There is an element of truth to this. If you drive your car into a concrete barrier, your chances of survival at 50 mph will be better than at 100 mph. But driving faster than the posted speed limit on multi-lane, limited access highways is not the primary risk factor for collisions. So many other things are more significant.

Driving while impaired by recreational substances (alcohol principal among them). Driving while distracted - by eating, smoking, talking on a cell phone, texting, fiddling with the radio. We've all seen some pretty ridiculous behavior at the wheel. Women applying make-up. Men shaving. Drivers reading maps and newspapers, text messages and emails. I'm pretty sure there have already been collisions caused by people driving while sneaking peeks at a smartphone screen, trying to think of the next move in "Words With Friends."

Aside from the fact that these impairments and distractions interfere with one's ability to respond quickly to unexpected changes in traffic conditions, they also make one's own driving erratic. Any of these things make it much harder to do what we should all be doing all the time on the highway: keeping the car centered in the lane. When you weave back and forth within your lane, occasionally straying over the line, you startle other drivers. That, in turn, distracts them. This sets up a domino effect of distractions, which is trouble.

One of the things all of us want when we're driving is for the behavior of all the other drivers to be predictable. And, to the greatest extent possible, we'd like it to be fairly uniform. And this is where the notion that "speed kills" is misleading.

Many years ago, civil engineers figured out that a good way to set speed limits was to observe driving behavior and use the 80th percentile. In other words, find a speed such that roughly 80 percent of the drivers were staying below it. And set that as the speed limit. Why? Because it was understood that minimizing variability promoted safety. If everyone is driving at about the same speed, that enhances predictability. And predictability of driving behavior makes it easier for everyone on the road.

Then along came the Arab oil embargo of the 1970s and a federal 55 mph speed limit. All of a sudden there were millions of miles of highway with a well-established record of safe driving with a speed limit of 70 mph that now had a 55 mph limit. And that introduced greater variability. Some drivers fearfully going 55. Others, accepting the stress of having to keep a sharp eye out for the highway patrol, and aided by radar detectors, going 75. Not good.

More recently the federal 55 mph limit has been repealed, although it is stubbornly persistent in places where the "nanny state" mindset prevails. Why? Because we hate it. It doesn't save lives, and the value of the time it wastes is perceived as greater than that of the extra fuel consumed in driving faster.

So what is happening in those places where the limit is still 55? You guessed it: more variability than ever. Lots of people who feel compelled to stick close to 55, and lots of others who think it's ridiculous and go 70-75. And, as if that isn't bad enough, many in the first group seem to prefer the left lanes.

Some older drivers just feel safer at slower speeds. That can create dangerous variability. Parts of Florida are especially troublesome, with a dangerous mix of young people in a hurry and older folks who drive like they're retired (because they are): "nowhere to go, and all day to get there." OK, fine. But please do it in the right lane!

I think to get a driver's license you should have to demonstrate not only that you know how to operate a motor vehicle and what your state's traffic laws are, but also that you understand the "rules of the road." Things like "slower traffic keep right" and "keep right except to pass." These are not things you must do to avoid being pulled over and cited. They are, however, things you must do to promote highway safety - and to keep other drivers from wishing they could target your vehicle with surface-to-surface missiles.

We cannot require everyone to take physics. But some simple concepts should be universally understood. Flow dynamics tell us that when vehicles are sorted by speed, with faster vehicles and slower vehicles grouped in separate lanes, traffic flows more smoothly. In other words, when we follow the rules of the road, everyone gets there faster and more safely.