Optical Illusion As Traffic Control

Status: Weird News
Chicago's transportation department has announced that they're going to try an interesting experiment to try to get people to slow down on a notoriously hazardous curve. They're going to use an optical illusion:
The yellow warning signs mounted along the road in recent years telling drivers to take the curve at 25 m.p.h. have had little or no effect. So the city has decided to try something new. In a few weeks, dozens of new pavement stripes will be laid down. At first they’ll be 16-feet apart, but as drivers get closer to the curve, the stripes will only be eight feet apart. "They provide an optical illusion that vehicles are actually speeding up and that causes motorists to slow down, which is of course, the intended effect that we’re trying to have at that location," said Steele.
Unfortunately there's no video of what this optical illusion effect looks like (the new stripes haven't been painted yet), but when I read this I immediately thought that if you combined the speeding optical illusion with randomly moving yellow lines, you could really mess with people's minds.


Posted on Fri Jul 28, 2006


We have these in Ottawa -- they really work! You can't really look at the road though, because you can get quite dizzy.
Posted by StarLizard  on  Fri Jul 28, 2006  at  04:56 PM
Here's one of the Ottawa ones on Google Maps:


It must work, because I've driven over that a bunch of times and always thought they were evenly spaced -- it didn't click that they got closer until I read StarLizard's comment!
Posted by rich  on  Fri Jul 28, 2006  at  06:14 PM
From the overhead photo, it's now obvious that they do get closer, and thanks, rich. I noticed that the lines are stopped prior to the actual sharp curve; they are on the approach to the curve. Wonder why they don't have any on the approach to the very sharp curve in the lower left? That one seems to be better banked, tho. All we have here is rumble-strips - oh, and since it's summer, lots and lots of orange barrels. But with gas at 3 bucks a gallon, why bother?
Posted by stork  on  Fri Jul 28, 2006  at  07:00 PM
I guess people slow down enough prior to the curve that the lines aren't needed in the curve itself. They really are distracting as well, I wonder if they might cause more harm than good in the curve?
Posted by StarLizard  on  Fri Jul 28, 2006  at  07:21 PM
It's actually not an experiment, the practice is common enough elsewhere (though maybe not in the US?) and proved to work well. Typical placement is near the bottom of a steep hill that approaches an intersection.
Posted by Wendy  on  Fri Jul 28, 2006  at  07:23 PM
We have stripes across the road on the approach to many roundabouts in the UK (for us pavement is what USAnians call sidewalk. We have pavement (kerb) stripes to show if stopping/loading is allowed). The strips closer to the roundabout are also raised slightly, just enough that you can feel them. I slow down because I know I am getting closer to the hazard, not because of any optical illusion.

Many curves here have black and white chevron boards all the way along them, but the chevrons are evenly spaced.
Posted by Sarah  on  Sat Jul 29, 2006  at  03:39 AM
Why are they going to so much trouble to protect drivers who simply go too fast? Since it's mostly single vehicle accidents that result from this situation just let natural selection take its course. Then after the crash take the driver out beat the shit out of them. Then maybe, just maybe, they might learn to slow down.

Near Vancouver, British Columbia, they are spending about $500 million to redo the highway that runs north to the Whistler ski resort which will be the site of the 2010 Olympics. That highway is notorious for regular deadly accidents because it is narrow and windy for much of its 100 km length.

The reason for all the accidents is simply excessive speed. Radar traps and warning signs don't seem to stop it. They really should be revoking drivers' licences and impounding cars for years but the government seems reluctent to do that. Instead, the highway is blamed. So now the taxpayer is on the hook for half a billion dollars so skiers can get to the slopes 10 minutes faster on Friday night.
Posted by Captain Al  on  Sat Jul 29, 2006  at  09:55 AM
This has been used in the UK for about 20-30 years and works very well.

In fact, I remember seeing a segment on an old BBC TV show - about 30 years ago - ("This Week in Britain") that showed the original experiments somewhere in southern England and how well it all worked.

It's very effective.
Posted by James  on  Sat Jul 29, 2006  at  10:05 AM
"Radar traps and warning signs don't seem to stop it".

I find this comment interesting. In Germany the speed trap, definitely has a "trap" feel to it, in my opinion. For example, I understand, it is illegal to warn other drivers, via gestures, that the police are around the next corner measuring speed. Definitely you should observe speed signs, but in an unfamiliar area it's possible to get caught out, because you missed the speed sign, for example. Also often speed changes are indicated by the colour of a place sign, not by a digit on a sign, as a foreigner you need to get used to it.

In the U.K. speed cameras are often heavily "advertised" via numerous road signs. Sometimes I've seen many many speed camera signs and not noticed an actual device. I find this method much more effective in reducing speed, rather than trying to catch people doing a misdeed.
Posted by Pixie  on  Sat Jul 29, 2006  at  01:25 PM
I don't see how this would work very well. Once I noticed the strips are closer together, I would no longer slow down. I can see how it would work at first but not for long.
Posted by Dae Dae  on  Mon Jul 31, 2006  at  10:52 AM
Yes, We have these in the UK too, usually on approaches to roundabouts. They really work, but as already stated, they can screw up your eyesight. Also when you've got used to a particular site you quickly realise you have an advantage over unfamiliar drivers, and learn how to overcome the "slowdown" effect. MADNESS!!!!! MWAH HA HA!
Posted by zap  on  Mon Jul 31, 2006  at  03:05 PM
optical illusions are always of great interest to me, great post.
Posted by Meet Women  on  Wed May 28, 2008  at  05:16 PM
Thanks for the wonderful information- just wondering if anyone else has had any relevant experiences to share
Posted by HGH  on  Sun Aug 30, 2009  at  12:23 PM
The ultimate irony here is perhaps that, as reports say, the 3D image is being used in an attempt to jolt reckless drivers into reality. What better way to get drivers back
Posted by carouser  on  Sun Sep 05, 2010  at  06:33 PM
This is pretty useful, im doing an optical illusion for road signs for my science fair project, and i think its pretty good, since i cant find any other road signs that are optical illusions.
Posted by sorry cannot be told  on  Tue Feb 28, 2012  at  03:32 PM
Commenting is not available in this channel entry.