Finally, there's an explanation for those wasted hours we spent on the MassPike today asking no one in particular "what the (dirty word) is this (dirty word)?" A team of mathemeticians from the Universities of Exeter, Bristol and Budapest developed a mathematical model revealing that traffic jams are caused by idiots. Okay, not exactly. The real explanation is that unexpected events, such as being cut off, require slowing below a threshold speed for smooth traffic flow. As we've all observed, when the car in front of you brakes suddenly, you need to brake even harder to compensate for your reaction time; this creates a wave that radiates back through traffic. That "backward-traveling-wave" means that because of one driver's inattention, we all pay for it miles behind. The results of the study really point up the need to drive smoothly. Roads with heavy traffic volume seem to be more prone to traffic jams, too, but that's not necessarily the case. Heavy volume can proceed smoothly if drivers anticipate and avoid sudden actions. In the end, it appears that the main way to fix traffic jams is driver diligence. The low-tech solution is to pay attention when you're behind the wheel, but we've also now got radar-based cruise control that does this for you, so you can continue blithely on your way. It boils down to common sense; be a smooth driver, expect that everyone around you is a moron, and hopefully you won't be slamming on your brakes, causing a domino reaction.
[Source: physorg.com via Motive Mag, Photo: Ed Edahl/FEMA]
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Reader Comments (Page 1 of 3)
zamafir @ Dec 21st 2007 8:14PM
... this just in, the sky is blue!
Seriously, it reminds me of an episode of topgear where Jeremy asked why anyone would ever use brakes on the freeway, it was funny at first but then had me thinking, if you're maintaining a safe distance, and driving at the speed limit, you should have enough time to react without sending shock waves of congestion.
Just yesterday the car behind the car behind me slammed into the car behind me simply because the driver wasn't looking ahead many many many car lengths out, it's a little entertaining that it takes a University study to add credence to common sense (the same common sense any racing school will teach, or good parent, or good friend).
Derek @ Dec 21st 2007 9:04PM
I rarely use my brakes on the freeway as well. Having a stick shift helps too. Wind resistance and engine braking combine to provide enough slowing in most situations unless traffic is really slowing to a crawl or I wasn't paying enough attention.
DW @ Dec 21st 2007 8:47PM
was the episode you're talking about the one where he does 800 miles in the A8 diesel? I remember him saying that to drive economically you have to really concentrate and never ever touch the brake (on the freeway). The same should go for all freeway driving in general.
The problem is that a lot of people just don't pay attention, they don't look far enough ahead, and they use their brakes for the most useless of actions (like to slow down 1mph). Not only would traffic run smoother if people did the opposite as i just stated, but it would be safer as well.
Also kind of goes hand in hand with how the feds are more concerned with making cars safer and letting people keep driving like idiots, than making drivers better and more alert.
Cornholio @ Dec 21st 2007 8:51PM
I've always felt that brakes should be a "last resort" in controlling the speed of your vehicle. proper following distance and throttle modulation can go a long way. This is another reason I prefer manual transmission cars - you can use engine braking to slow down simply by lifting off the throttle a bit.
There's nothing more infuriating than following someone who can't decide how fast they want to go. PICK A SPEED ALREADY! Why this is such a hard concept is lost on me. And we've all seen the resulting ripple effects.
paul34 @ Dec 22nd 2007 12:14AM
Absolutely. This is definitely a "duh" thing. Traffic situations are caused by indecisive, poor drivers who often are poorly trained slushie drivers who slam the throttle to move up one inch, then slam on the brakes to stop again. Not necessary - just let a certain distance build, then just cruise with your feet off all the pedals. Never stop.
I agree with Jeremy when he said that. That's what I've always done. To me, to use the brake is "failure" of sorts - it's sort of a game for me. Don't get me wrong, I don't take reckless chances to avoid using the brakes, but I do always plan ahead such as to drive in a way to minimize my brake usage.
I also drive a manual, so yes, passive engine braking available in the gear you're already in helps quite a bit. At any rate, though, it's true. You really shouldn't have to use your brakes that much.
The only times I have to are when traffic is heavy. People becomes 1000x more stupid when that happens, and you just have to hit your brakes to avoid hitting the idiots who constantly cut you off, slam on their brakes ahead of you for no reason and come to complete stop for many seconds, slow down to 30 MPH for a 40 MPH ramp, etc.
Heh, I tell people that "I don't really drive fast, but I also don't slow down," and it is true =)
Dan Roth @ Dec 22nd 2007 12:21AM
All you guys touting the engine braking available with manuals realize that the very same effect is present in most modern automatics, right? A lockup torque converter provides the same solid link between crankshaft and tranny input shaft. I use engine braking all the time in my automatic transmission (purchased for a multitude of reasons, next one will be a stick, I swear!) car.
Whitie @ Dec 22nd 2007 8:56AM
Around here, the road cloggers are international types driving international cars. I see it all the time.
I prefer Germany where a drivers license is not a birthright.
J M C 3 @ Dec 22nd 2007 10:48AM
This afternoon I was rudely awaken from my afternoon nap...by this GUY, HONKIN' HIS HORN IN BACK OF ME!
dan @ Dec 22nd 2007 1:16PM
Something to consider when touting engine braking is that there is a reason brake lights are classified as safety equipment.
Billy @ Dec 21st 2007 8:18PM
The key phrase in the whole article is "expect that everyone around you is a moron"
That pretty much sums up my morning commute
Mark @ Dec 21st 2007 9:58PM
x2
Travis Rassat @ Dec 21st 2007 8:23PM
I've been saying this for quite some time. A little courtesy goes a long way. Keeping a safe following distance and using less brake improves mileage, too. I hope this study makes the rounds on the major news sites and shows so maybe a few people will listen.
Paul H. @ Dec 21st 2007 8:28PM
Did they also figure out that drunk driving is a result of too much booze?
Eisenfaust @ Dec 21st 2007 8:47PM
And yet, people get furious with me when I maintain a 3 second following distance on the freeway in dense traffic, so that I DONT have to slow down a great deal when the person in front of me isnt driving smoothly.
HarryJames @ Dec 21st 2007 8:53PM
Stop following so closely to the car in front of you and when changing lanes, please use signals. It's not that hard and only takes a half second to use.
dave0mary @ Dec 21st 2007 9:03PM
It drives me NUTS when you are driving on a crowded expressway at rush hour - but the traffic is moving ... until you come to a hill. I use my speed cpntrol almost exclusively. W/O a speed control, as you go up a hill, with your accelerator in the same position, you slow down. BACKLOG of traffic. Please use your speed control.
ermax18 @ Dec 21st 2007 9:12PM
I don't think it is simply that the incline slows the cars but that people are paranoid that they can't see what is on the other side of the hill. Yet they have no problem riding 5ft off the bumper of an SUV (blind spot) at 80mph.
NewJerseyBMW @ Dec 21st 2007 9:04PM
God help that person when I snap.
sylvesterscott @ Dec 21st 2007 9:07PM
hahahahahahahaha... it took them a study by mathematicians to figure this preposterousness!!
Brilliant! Although the chances for who ever wanted the study done, to come to me for answers is very unlikely, i would have given them the exact terms and phrases( or similar) about why there are traffic jams. half the reason is simple common sense, that most drivers are monkeys that are driving because they can. if proper tests were made for getting your license, there would be better drivers. but no one cares, everyone wants to do the thing that they want to do, cause thats how they are, or they believe paying their taxes makes their driving style being of no one's concern. The bottom line is that if everyone moved at a brisk pace, stayed in their respective lanes, changed only when needed to overtake(necessarily) or taking an exit, there would be no 'rush hour'!!! also, while in a exit lane, move faster, because you are holding up vehicles behind you that is creating the 'ripple' effect of traffic. just because you are off the highway( for instance), does not mean you don't need to drive faster. you are not going to get a ticket nor is your car going to fall apart if you drive a little faster in an exit lane. comon people!! atleast think of the air/environment around, YOUR INEPTNESS to drive a bit better on the road is causing SO MANY ISSUES!!!
Dan Roth @ Dec 21st 2007 9:37PM
It's kind of ridiculous that they had to do a study to get some kind of official answer to what everyone could have already told them, yes. However, on and off ramps are the proper place to slow down. Maybe you live in an area where you can actually speed up on the ramps, but we have some very short ramps here in Massachusetts that were neither designed for the speed or volume of traffic we have today.
The proper way to exit the highway is to maintain your speed until you're in the exit lane, then use your brakes. If you're going the correct speed, you should have plenty of room to slow down.