'Just that you do the right thing. The rest doesn't matter. Cold or warm. Tired or well-rested. Despised or honored.' -Marcus Aurelius

Driving Slow and Fast Are Equally Dangerous

by Ethan Glover, Mon, Nov 20, 2017 - (Edited) Wed, Dec 06, 2017

Americans don't know how to drive. The first thing people told me when I got a car in Germany was to not mess around on the Autobahn. They weren't telling me to not drive fast, as is the norm. They were telling me to not drive slow. Don't spend too much time in the left lane because you'll get run over. Not literally... but you've never been tailgated until you've had a V10 supercar on your ass, inches from your car, flashing lights at you. No one in Germany is sympathetic towards the one who gets tailgated in that situation, including the police. You shouldn't have been in the wrong lane. (That was my BMW to the right, and yes I've made that mistake of hanging out in the left lane.)

The United States has 12.9 road fatalities per 100,000 vehicles every year. Germany has 6.8.

According to a GMAC 2010 study, only 77.9% of Americans on the road today could pass a driving test if they had to take it again. 37% of the women surveyed failed while 13.6% of men failed. Those living in the Midwest scored the best while those living in the Northeast scored the worst.

But what's the problem that causes so many accidents? While its hard to get reliable statistics, most sources point to speed variance. A 1964 paper by David Solomon which created the 'Solomon Curve' showed as much. Subsequent studies solidified this theory in 1968, 1970, 1991, and 2001. Variations from Solomon's findings have suggested that there is A) no difference between risks at faster and lower speeds compared to mean traffic and B) the casualty risk is lower at lower speeds. The most important thing in this case, however, is that variance from the average traffic speed causes accidents.

We all know how fast drivers can be a risk. Their reaction times are significantly reduced, braking distance increases and loss of control over the vehicle is much more likely. But it's not the increased speed that causes accidents necessarily. It's variance. So what's the problem with slow drivers? The short answer is that faster traffic has to react to them.

  1. Slow drivers increase the risk that people pass at the wrong time on single lane roads.
  2. Slow drivers in a left (passing) lane on the highway can cause other vehicles pass on the right, causing congestion and more accidents.
  3. Slowing down when changing lanes causes congestion and accidents. (See above source.)
  4. If a large truck such as an 18-wheeler has to pass a smaller vehicle on the highway, they will not be able to accelerate quickly. This causes congestion behind them in the passing lane.
  5. Slow drivers who are cautious when merging onto the highway rather than matching the speed of everyone else cause congestion. (See above source.)
  6. Driving too slowly on curves can cause congestion. (Esurance)

(Esurance recommends flashing your lights or tapping the horn while keeping your patience if you get stuck behind a slow driver.)

That's a lot of 'causing congestion' and not a lot of 'causing accidents.' But these two issues are one in the same. Do the research (or read the sources linked here) and you'll find that there are two things that researchers point to as the primary cause of vehicular accidents. Speed variance, and congestion. Or more specifically, too many cars in one place and not enough free-flowing traffic.

When traffic becomes congested, reaction times reduce and braking times reduce. To understand how dangerous it is, you have to understand phantom traffic jams. Explained below by traffic engineer Brian Wolshon.

It doesn't matter where you're at, or what the road conditions are, stay with traffic. If there's a little snow and everyone around you is still going 65, it's safe to go 65. As a rule of thumb, if you're nervous, follow an 18-wheeler. They're the slowest vehicles on the road, if you can't keep up with them, you don't need to be there. Get an Uber. (In worst case scenarios you can follow a salt truck but turn your warning lights on and keep your distance.)

On clear days, just follow the speed limit, if everyone is going 5 over, go 5 over. If everyone is going 5 under, go 5 under. You can be the guy that insists on going exactly the speed limit but pay attention to the people behind you and in front of you. Is there a line of cars behind you? Pull over and let them pass. Are you passing people at such a fast rate on the highway that if someone made a sudden lane change you wouldn't be able to stop? Slow down. Do you just want to go 5 mph more than everyone else? Pass in the left lane, get back in the right the second you're past. You should never have empty space to your right in another lane.

Remember, speed is relative. If you're driving 55 in a 65mph zone, you make the people driving at a normal speed "fast drivers." But it's not them causing the problem. Stay consistent, look around and use others to determine what your speed should be. You're likely to save a life that way.