Going Slow To Go Fast

I thought I would share this article, titled “Go Slow To Go Fast: Why highways move more swiftly when you force cars to crawl along at 55 mph” and get your comments.

What do you think?

The I-70 mountain corridor is a rather unusual piece of highway.

I think that line from the article tells us everything we need to know. These tactics might work on unusual highways, but on flat highways in Texas where you could do 90mph all day and not see anything but a dust devil, artificially slowing traffic to 55 would be silly.

I-70’s problem is that it’s in the mountains, and fully loaded semis don’t do well on steep grades. So you have trucks crawling along while cars try to go fast. The speed differential aspect of the article is true, but I don’t think the proper answer is to force everyone to go the same speed as the slowest vehicle out there.

Based on other traffic studies that I’ve read, what causes backups is what one researcher called the slinky effect. A car up in front of the pack hits the brakes for whatever reason, or no reason at all. All the cars behind him then do the same (hopefully), but because humans aren’t perfectly synchronized with each other, each person brakes slightly longer than the guy in front of him. You end up sending what looks like a compression wave through the traffic - just like if you stretch a slinky out quickly and then stop moving your hands. On lightly-trafficked roads, that’s not a big deal. The slowdown is absorbed by the empty space between cars. But in rush hour on a busy highway, the slinky effect means that about half a mile or so back from the guy who hit the brakes first, cars are on the brakes for seconds at a time, which has a serious impact on traffic speeds. That’s how a lot of traffic jams form - often without any actual reason, which is why you’ll be crawling along at 5mph for half an hour and then suddenly the road clears out in front of you, and the wreck you expected to see as the cause isn’t there.

I can see where having people go slower would help in that situation because the faster you go, the more you tend to want to slow down when you think the guy in front of you might be stopping. Psychologically a crash at 70 is a lot more intimidating than a crash at 55, and so you brake harder and probably stay on the brakes longer, exacerbating the slinky effect. However, if it’s a regular stretch of highway, slowing the speed limit down won’t do all that much, I don’t think, because when traffic gets heavy, drivers slow down anyway.

The real answer is better public transportation, which has the double benefit of getting people who ride it where they want to go faster than sitting in traffic, and getting a lot of the cars causing the traffic off the road entirely.

Check out this demonstration:

I agree that public transportation is the best solution for this and other problems, like pollution, but in lieu of that, since large spending projects are unpopular right now, I think this would go a long way in relieving congestion.

Oh, and I don’t think this problem is present to the same degree in Texas. In Texas, when you speed, you get caught. They actually enforce the law in Texas, and that’s a game changer by itself.

The problem I always had with the rice experiment is that in extrapolating to traffic issues, it assumes that either the rice is self-aware, or drivers aren’t (which, admittedly, could probably be successfully argued in many cases :wink: ). People do dumb and/or selfish things - things which would not happen if they were just drifting uncontrolled down through a funnel hole. In reality, the gaps created by pouring the rice slowly would be exploited by that self important rice grain which is too much of a jackass to even consider not cutting in front of all the other rice.

This experiment has been used to justify metered on-ramps, which are at every on ramp in my city, and we still have lengthy traffic jams.

If you really wanted to extrapolate the rice experiment to real life, you’d embark on a program which encourages workplaces to vary the start and end of the work day so that everyone isn’t jamming onto the freeways between 4:30 and 5:30. As it is, you’re going to have basically the whole city trying to use the freeways at the same time, once in the morning, once at night, and artificially slowing that down isn’t going to help because it’s already crawling along below 10mph.

The key is ‘rolling speed harmonization’. The speed number matters not.
The core problem is that people are selfish.

They enforce the laws in Texas?? Not in my part. The “slinky” effect Shadowfax defined down here I just call I-35. Every…Single…Day…which is why I don’t take it. :slight_smile:

“They enforce the laws in Texas?? Not in my part.”

They did when I lived there and learned to drive (in the Dallas/Fort Worth area). I was busted several times for speeding in Texas. After I moved out of the state, the frequency of tickets went down, and my driving style didn’t mature for another decade.


As the article indicates, sped differential is the problem. I95 between DC and Baltimore has a construction project going on. The highway folks posted signs that say the speed limit is 65, as always, but this time they really mean it. Still, there are people that just can’t believe the signs and slow down well below 55. This seems to slow traffic to near zero. Every day.

That stretch of I-95 is difficult for the daily commuters there it seems. And for a tourist like me it was mayhem even at 5:00 a.m. I may take the DelMarVa peninsula on my next excursion. A 55 mph speed limit would seem to be appropriate there.

I regularly drive stretches of interstate where the “idiot” issue is the issue. In other words, outside of certain small areas at certain times of day, short of idiots the roadways flows quite nicely and safely. All it takes is one idiot - but obviously there are always more than that. (At those congestion times and places the premise of this article makes sense and it is the logic I follow).

The author of this piece is one of the idiots - I can tell. There is no such thing as a “fast” lane. And this is one of the things that people don’t understand. There is a passing lane - and you use it to pass people (or make way for traffic entering from ramps which is the same thing). And if you’re not passing someone then you do not belong in the “passing” lane. The more people believe there’s a “fast” lane and “slow” lane the more people completely misunderstand the design logic of multi-lane, limited access highways…and the more they go out there everyday and create completely unnecessary traffic problem - and DANGER.

Of course, a note to add is that predictability/consistency, mostly of speed, has to be included in there as unpredictability makes the orderly use of passing lanes to pass a little difficult.

" There is a passing lane…"

How long does it remain a passing lane until it fills up with traffic and stalls like all the other lanes? I often encounter enough traffic at 6AM that all lanes slow to 45 to 55. I also know that it is worse in Northern Virginia or on I-270 in MD where traffic is often crawling along at 25 in some stretches at the same hour.

Well, that’s what I was implying about variations in roadways and then those certain times and places…On the stretches I drive 90% of slowdowns I encounter are not created by traffic volume. They’re just created by drivers who don’t know how the roads work and don’t pay any attention at all.

But I’m also not talking about DC area roadways - or similar. Even so, traffic flows most smoothly when everyone does this to the best of their ability. Its just that one is not always able, and that’s the way it goes. At those time, the rice funnel generally makes more sense.

Probably the best solution would be variable speed limits on major highways depending on the time of day and traffic conditions, similar to what they do on the Autobahn. But I have to admit that Grandma in her Park Avenue probably isn’t ready for that over here. And of course no one would want to pay for the upgrades.

@cigroller: “There is no such thing as a “fast” lane. And this is one of the things that people don’t understand.”

You seem hung up on labels. I suggest to you that if it was named for how it is used, and not how YOU think it should be used, it IS a fast lane, not a passing lane. If it’s not a “fast lane,” why is it where they usually locate the HOV lane?

Don’t you love it how, when someone doesn’t hold the same viewpoints as you, that person becomes an “idiot,” whether or not the person is ACTUALLY an idiot? Something tells me that if you were to talk to the author face-to-face, and gave him a chance to answer your objections, you might find he’s a pretty smart guy.

Sorry Whitey. This has nothing whatsoever to do with what “I” happen to think. It is also not at all about labels. It is a passing lane - that’s how limited access highways are designed. Its how every responsible driving ed program explains it. It is what makes highways work. If people “pick a lane” rather than picking a speed and staying right except to pass then they make a mess out of the highways. Drivers using the left lane for things other than passing are obstructing traffic and are defeating the entire purpose of multilane highway designs. There are obviously situations where traffic volume doesn’t allow such a neat picture of things - but even a lot of those situations are caused by people not following the simple stay right except to pass rule. I see it every single day when I drive - unnecessary congestion and unnecessary danger created by people who are obstructing traffic by failing to observe this simple rule.

In fact the “stay right except to pass” principle is so basic and fundamental (up there with come to a complete stop at a stop sign) that I’m really surprised that you are disputing it. Its not merely something like an “opinion.”


I can pull them all day long and they all say the same thing - stay right except to pass. I’m sure you’ll go turn over a few rocks to dig up a few now that say something different - but if you find them there aren’t many and they are irresponsible.

The far left lane cannot be exclusively for passing. It will be bumper to bumper and crawling just like the other lanes in a traffic jam.

Well, Rod, that kind of depends on where and when you’re talking about now doesn’t it? Every one of my posts up here emphasized the fact that varying traffic conditions in various places can make things different. This is especially in an around cities and in & around rush hour types of times.

YES - the far left lane CAN only be used only for passing in many many many places and times. And when its not that how you get bumper to bumper traffic.

If you’re just talking about during a traffic jam - then obviously none of this applies at all.

But I have literally - with my own eyes - seen people turn free flowing multilane highways into traffic jams. Simply by not following the very basic stay right except to pass rule.

What about states where it is legal to pass in any lane?

What about them? If I had to vote on whether or not to make it illegal to pass on the right I wouldn’t vote in favor. People have to have a way to get around those who obstruct traffic by riding the left lane without purpose. I sometimes have to do it. I see other people forced to do it.

I honestly don’t even know what the laws are in my own state. Whether any of it is legal or not is completely irrelevant to the fact that the whole design of these things is meant to work this way.