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Old 05-05-06, 01:17 PM   #1
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Optical Illusions To Reduce Speeding

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How do you get drivers to slow down on dangerous roads? Virginia transportation officials think you can trick them with an optical illusion and they're giving it a test on one hazardous boulevard in Fairfax County.

In just a few short hours, VDOT crews put down some strange-looking markings on a section of a two-lane winding road to try to make it safer.

Last summer on a half-mile stretch of Lee Chapel Road between the Fairfax County Parkway and 123, a teenage girl was killed when she ran off the side and hit a tree. That tragedy, plus a high accident rate overall, put pressure on VDOT to do something.

It led to this pilot project, a first in Virginia. They’re called speed bars.

Pieces of white road tape are melted to the pavement on each side of the road. They're placed at decreasing intervals to basically trick drivers into thinking they're going too fast.

VDOT researchers found 85% of the drivers on this stretch speed considerably over the 40 miles per hour speed limit. Traffic engineers will evaluate speed data next week and again in three months to see if the optical illusion is doing the trick.

Optical speed bars are being used in several places in the United States. But they've been used longer in Britain where a study found speed bars reduced both fatal accidents and those with serious injuries.
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Old 05-05-06, 01:41 PM   #2
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Sounds interesting.

But I wonder (without image of the lines) if they may make a rideable shoulder less rideable due to paint strips, which most often create a mini bump due to thickness of 'plastic paint stuff' in addition to slickness factor when wet.

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Old 05-05-06, 01:43 PM   #3
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I wonder if drivers will figure them out, learn to compensate, and go back to driving the same old way. It seems that a lot of traffic calming measures like this have only short-lived effectiveness.
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Old 05-05-06, 02:04 PM   #4
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This kind of system has been used in the Uk and I think other parts of Europe for nearly two decades now. To the best of my knowledge then don't lose much effectiveness as they act on the periphery of the vision and stimulate an involuntary reaction.

There will always be some people who conciously attempt to beat the system but you have to be thinking about it at the time.
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Old 05-05-06, 03:12 PM   #5
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Interesting for short distance solutions I suppose.
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Old 05-05-06, 07:52 PM   #6
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This is somewhat of a sidetrack, but...

I've always wondered if high freeway speeds condition drivers into driving faster in suburbs, cities.

Here in AZ freeway SL is 75mph, 85mph is the normal speed. Urban freeways are 65mph, 75mph actual. When folks exit those urban freeways (that go all over the city) onto a 45mph arterial, 45mph feels very slow after cruising at 75 on a freeway that doesn't seem much different than a 7 lane arterial.

Drivers get condtioned into 'normal' speed. When I stopped being a speeder 5yrs. ago it took a month or more until I reconditioned into feeling 'normal' at the SL. Now I don't feel slow at all.

Al
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Old 05-05-06, 11:01 PM   #7
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more "sleeping policemen".... making roadways safer via traffic calming, speed control, and awareness gauntlets....
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Old 05-05-06, 11:55 PM   #8
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Quote:
Originally Posted by Bikepacker67
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How do you get drivers to slow down on dangerous roads? Virginia transportation officials think you can trick them with an optical illusion and they're giving it a test on one hazardous boulevard in Fairfax County.

In just a few short hours, VDOT crews put down some strange-looking markings on a section of a two-lane winding road to try to make it safer.

Last summer on a half-mile stretch of Lee Chapel Road between the Fairfax County Parkway and 123, a teenage girl was killed when she ran off the side and hit a tree. That tragedy, plus a high accident rate overall, put pressure on VDOT to do something.

It led to this pilot project, a first in Virginia. They’re called speed bars.

Pieces of white road tape are melted to the pavement on each side of the road. They're placed at decreasing intervals to basically trick drivers into thinking they're going too fast.

VDOT researchers found 85% of the drivers on this stretch speed considerably over the 40 miles per hour speed limit. Traffic engineers will evaluate speed data next week and again in three months to see if the optical illusion is doing the trick.

Optical speed bars are being used in several places in the United States. But they've been used longer in Britain where a study found speed bars reduced both fatal accidents and those with serious injuries.
You mean they think people are actually paying attention to the road? Hard to believe.
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Old 05-06-06, 12:16 AM   #9
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Quote:
Originally Posted by Bikepacker67
Pieces of white road tape are melted to the pavement on each side of the road.
Gawd I hate those things! They're at least 1/4" high. Doesn't feel like anything in a car, but on a bike its WHUMP WHUMP WHUMP WHUMP.
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Old 05-06-06, 06:54 PM   #10
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Don't you mean: "WHUMP s@$t! "WHUMP" [insert other 4 letter word] "WHUMP" My a$$! "WHUMP"
The heck with this. I'm going to ride in the lane.
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Old 05-06-06, 11:10 PM   #11
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Maybe a giant spike on the steering wheel...
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Old 05-07-06, 12:01 AM   #12
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Quote:
Originally Posted by DataJunkie
Don't you mean: "WHUMP s@$t! "WHUMP" [insert other 4 letter word] "WHUMP" My a$$! "WHUMP"
The heck with this. I'm going to ride in the lane.
Usually those paint mountains are IN the lane. Recently they seem to have become more popular with the authorities. Some lanes are like riding on an alphabet soup of messages and arrows. Between those and the hockey puck reflectors sometimes the road feels more like riding off-road. They make it hard to brake evenly, too. Don't get me started on those grooves they cut into the road ahead of some stop signs....
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Old 05-07-06, 06:13 AM   #13
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Quote:
Originally Posted by noisebeam
Drivers get condtioned into 'normal' speed.
Yesterday I drove about 5 hours (RT) to help someone move. First time I've driven my car in a couple of weeks, and first time on the expressway in months. I found that I was comfortable driving 45 in the 55 zones, and when I got on the expressway (70 MPH limit) I drove the whole way at 60 instead of my usual 75, it felt "normal" and as a bonus, my mileage jumped from 24 to 29. I was mainly checking what my mileage difference would be, but it was surprising how it didn't feel "slow".
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Old 05-07-06, 08:53 PM   #14
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Quote:
Originally Posted by DCCommuter
I wonder if drivers will figure them out, learn to compensate, and go back to driving the same old way. It seems that a lot of traffic calming measures like this have only short-lived effectiveness.
--- Seems to me the optical speed bars would work best on roads which are traveled by out-of-towners who are unfamiliar enough that they won't figure them out.
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Old 05-07-06, 09:29 PM   #15
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Quote:
Originally Posted by Bikepacker67
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How do you get drivers to slow down on dangerous roads?.....

Well, ya can't be there all the time. But don't forget...stick to the speed limit yourself and watch the speeders pile up behind you.

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Old 05-08-06, 04:37 AM   #16
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Quote:
Originally Posted by DCCommuter
I wonder if drivers will figure them out, learn to compensate, and go back to driving the same old way. It seems that a lot of traffic calming measures like this have only short-lived effectiveness.

We have similar things in Arkansas. The difference is that at the end of the stripes, theres a gnarly speed bump. It seems to work.
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Old 05-08-06, 06:42 AM   #17
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Quote:
Originally Posted by noisebeam
This is somewhat of a sidetrack, but...

I've always wondered if high freeway speeds condition drivers into driving faster in suburbs, cities.

Here in AZ freeway SL is 75mph, 85mph is the normal speed. Urban freeways are 65mph, 75mph actual. When folks exit those urban freeways (that go all over the city) onto a 45mph arterial, 45mph feels very slow after cruising at 75 on a freeway that doesn't seem much different than a 7 lane arterial.

Drivers get condtioned into 'normal' speed. When I stopped being a speeder 5yrs. ago it took a month or more until I reconditioned into feeling 'normal' at the SL. Now I don't feel slow at all.

Al
Reports have shown that speeding in urban areas is usually caused by the type of road. On narrow, two lane roads, drivers instinctively feel they can't go very fast, so the speeds are slower. But take the same road, leave the marked speed limit, say 30 mph, make it four lanes with a median, and now the speed jumps dramatically.

The report basically says that drivers will drive as fast as they feel comfortable going, regardless of the speed limit. Wide multi lane highways make them feel comfortable so they go fast, on narrow two lanes they are not as comfortable so they slow down.
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Old 05-08-06, 11:31 AM   #18
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Originally Posted by San Rensho
Reports have shown that speeding in urban areas is usually caused by the type of road. On narrow, two lane roads, drivers instinctively feel they can't go very fast, so the speeds are slower. But take the same road, leave the marked speed limit, say 30 mph, make it four lanes with a median, and now the speed jumps dramatically.

The report basically says that drivers will drive as fast as they feel comfortable going, regardless of the speed limit. Wide multi lane highways make them feel comfortable so they go fast, on narrow two lanes they are not as comfortable so they slow down.
I've read something about that theory before. They called it "natural speed" and tagged it as the 85th percentile speeed. (85% of drivers at or below that speed.) The basic idea was as you say, drivers tend to cluster near the highest speed that feels comfortable on any given road.
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Old 05-08-06, 11:38 AM   #19
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Originally Posted by DrCycleMrDrive
I've read something about that theory before. They called it "natural speed" and tagged it as the 85th percentile speeed. (85% of drivers at or below that speed.) The basic idea was as you say, drivers tend to cluster near the highest speed that feels comfortable on any given road.
Right, and my point was that with high SLs on freeways, drivers develop more comfort at higher speed. A 7 lane arterial after driving at 85mph on the freeway feels comfortable at 55mph, even if posted 40mph.
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Old 05-08-06, 11:55 AM   #20
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It's all relative though. 85 in a 70 and 55 in a 40 are essentially the "same" speed, b/c they are 15mph above the posted speed limit.

The posted speed limit is generally the 85th percentile speed, with the 100th percentile speed being the actual design speed of the road. The comfortable speed on roads is very closely related to design speed of the roadway and obstructions. As stated above, if you make a road 2 lanes in each direction with 12-ft lanes vs. 11- or 10-ft lanes, and you open up the horizontal and vertical curves for increased visibility, you will notice a comensurate increase in traveling speed.

If you narrow up lanes, the driver speed will decrease comensurate to the lane width. If you put barriers on one side, you will also see a decrease in speed. It's simply an unconscious reaction. Traffic engineers have been studying it for 50+ years.

I do like how they are taking a second study 3 months from now. That will give them a good data spread, and will let them know how fast people are driving once they are "used to" the stripes.
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Old 05-08-06, 12:06 PM   #21
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It's all relative though. 85 in a 70 and 55 in a 40 are essentially the "same" speed, b/c they are 15mph above the posted speed limit.

The posted speed limit is generally the 85th percentile speed, with the 100th percentile speed being the actual design speed of the road. The comfortable speed on roads is very closely related to design speed of the roadway and obstructions.
85 in 75 is 10mph over. The point I am making is that drivers get used to speed independent of road type. I live on a freeway access road and drivers exit at 75mph and even though the access road is narrower with not shoulder and 40mph posted, drivers typically go 65mph on the access road. They are numb to the speed they are going. 40mph after driving at 75mph feels like standing still, even on a narrow side street.

85% is NOT 85% of the 100% design speed. It is the 85th precentile measured speed on a road after it is build. Settting SLs has become less and less about designed speed and more about the speed most everyone is driving - independent of the varying driving enviroment (x-walks, cyclists, range of driving abilities)

Al
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Old 05-08-06, 08:40 PM   #22
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