# Traffic Lights



## gafftapegreenia (Sep 18, 2007)

Ok, random yes, but they do have some theatrical ties:
All questions refer to American-style, traditional, 3 color, incandescent, non-LED traffic lights.

What are the two common diameters of traffic lights available?

What type of reflector is used in a traffic light?

What type of glass lenses are commonly used? (I'm looking for a more blanket term here, as there are several different varieties of lenses from the past and the present, however, for reference, there are about 2-3 dominant styles)

What is the official name for the "blue green" color seen on some traffic lights? Where did this color originate and why was it needed?

What might we call the two styles of visors found on traffic lights in the theatrical world?

Before LED's, how was the "green arrow" produced?

Well, have at 'em.


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## jonhirsh (Sep 18, 2007)

What are the two common diameters of traffic lights available?
im going to guess 11" or 12" and 6" to 8"

What is the official name for the "blue green" color seen on some traffic lights? Where did this color originate and why was it needed?

- i have never seen that before.

What might we call the two styles of visors found on traffic lights in the theatrical world?

-Top Hats?
- Barndoors?

Before LED's, how was the "green arrow" produced?
Well, have at 'em.
-it was black painted on the glass leaving the arrow shape unpainted.


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## gafftapegreenia (Sep 18, 2007)

Yes, the two standard sizes are 8" and 12".

The arrow was indeed painted on the lens.

Traffic lights today have full visors, and many of the older ones had "cut-away" visors. We might call these top-hats and half-hats.

Good job so far.

Some green lenses are a more "primary green", while some are a "blue green". Again, why this blue-green color and where did it originate?


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## Charc (Sep 18, 2007)

gafftapegreenia said:


> Yes, the two standard sizes are 8" and 12".
> The arrow was indeed painted on the lens.
> Traffic lights today have full visors, and many of the older ones had "cut-away" visors. We might call these top-hats and half-hats.
> Good job so far.
> Some green lenses are a more "primary green", while some are a "blue green". Again, why this blue-green color and where did it originate?



In the city of Philly we have a mustard yellow color. Not to say I haven't traveled, but I've not ever paid an extreme amount of attention to the color of traffic lights in other cities...

I have noticed, recently, I believe I was in Hartford, a black oval with white stripes surrounding the traffic signal... I'm not sure why.


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## gafftapegreenia (Sep 18, 2007)

Interesting. While my topic is concerned to the actual optics of a traffic light, there are actualy many collectors out there with literally hundreds of traffic lights, and they pay top dollar for rare or old ones. So you see, those of us who love the old lighting instruments are quite normal. 

The black ovals that surround traffic lights are to block out background light, thus increasing visibility by seperating the traffic light from the surrounding enviroment.


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## Charc (Sep 18, 2007)

gafftapegreenia said:


> Interesting. While my topic is concerned to the actual optics of a traffic light, there are actualy many collectors out there with literally hundreds of traffic lights, and they pay top dollar for rare or old ones. So you see, those of us who love the old lighting instruments are quite normal.
> The black ovals that surround traffic lights are to block out background light, thus increasing visibility by seperating the traffic light from the surrounding enviroment.



Philly can't pay for black ovals. We can't stop the unbelievable murder rate either... 

(Speaking of murder rate... my school is in the middle of a not so nice neighborhood. In fact the drama teacher at the public high school around the corner had his neck broken when he confiscated a students iPod. I, and a number of other friends and classmates have gotten jumped. I always lock my car doors while driving around school.)


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## Van (Sep 18, 2007)

gafftapegreenia said:


> ..............................................................
> Some green lenses are a more "primary green", while some are a "blue green". Again, why this blue-green color and where did it originate?


The only thing I know about glass is that you get blue-green from altering the Selenium content, don't ask me how I know, it just got stuck in there. So is it "selenium-Green" ?


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## gafftaper (Sep 18, 2007)

My guess is that they added the blue to the green to help people who are color blind. 



Oh and the school I taught at was tougher than yours Charc. There was a drive by shooting of the bus stop across the street from the school, when her daughter was busted for being in a fight a mom came to school and beat up the security guy-mom & daughter left in cuffs together, there was the day we were locked down because a dangerous guy escaped from the minimum security mental institution down the street, and finally they found a dead body on the running track one morning before school. Ahh how I miss the good old days!


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## Charc (Sep 18, 2007)

gafftaper said:


> My guess is that they added the blue to the green to help people who are color blind.
> Oh and the school I taught at was tougher than yours Charc. There was a drive by shooting of the bus stop across the street from the school, when her daughter was busted for being in a fight a mom came to school and beat up the security guy-mom & daughter left in cuffs together, there was the day we were locked down because a dangerous guy escaped from the minimum security mental institution down the street, and finally they found a dead body on the running track one morning before school. Ahh how I miss the good old days!



Haha, touché Gaff, touché. It may be tougher, but it's still annoying having to look over your shoulder. Especially 'cause we're seen as the obnoxious rich kids, we get a lot of verbal confrontations, threats, etc.

Oh to the blue green. You might the green traffic light? I thought you might the instrument as a whole. I didn't mean to imply we have yellow-green signals.


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## Charc (Sep 18, 2007)

gafftaper said:


> My guess is that they added the blue to the green to help people who are color blind.
> Oh and the school I taught at was tougher than yours Charc. There was a drive by shooting of the bus stop across the street from the school, when her daughter was busted for being in a fight a mom came to school and beat up the security guy-mom & daughter left in cuffs together, there was the day we were locked down because a dangerous guy escaped from the minimum security mental institution down the street, and finally they found a dead body on the running track one morning before school. Ahh how I miss the good old days!



P.S.

Wasn't your school also the one with the special ed puppets hung in a noose in the proscenium wall?


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## gafftapegreenia (Sep 18, 2007)

The colored blind reason is mainly the reason why the color is still used.
However, it's not why this color was created originally. Why would a company such as KOPP offer blue-green lenses? What industry is KOPP historically known to make lenses for? Think about the earlier uses of lenses and different illumination sources.


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## jonhirsh (Sep 19, 2007)

Lol are you insinuating that KOPP had an extra supply of bluish green Roundels just sitting around so they sold them to the trafic light industry?

Something about that seems kinda wrong to me  I would hazard to guess that the trafic light industry let us use there technology....
JH


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## gafftapegreenia (Sep 19, 2007)

jonhirsh said:


> Lol are you insinuating that KOPP had an extra supply of bluish green Roundels just sitting around so they sold them to the trafic light industry?
> Something about that seems kinda wrong to me  I would hazard to guess that the trafic light industry let us use there technology....
> JH


 Not at all. Blue-green was in use before traffic lights.


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## dvsDave (Sep 19, 2007)

Oddly enough, I've got a real decommisioned traffic light from the 60's that I've been meaning to convert to a DMX interface for about 3 years now. 

Add in the lights, fit an internal power pack and DMX interface and create a versatile mounting system for rigging the light.

If anybody is interested, I can see about providing pictures and dimensions.

-David


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## gafftapegreenia (Sep 19, 2007)

Ah, Dave, that's awesome. I've been wanting to do something light that. I think that, as an instrument, traffic lights have underutilized design possiblities. Can you imagine a whole rig of traffic lights circuited to do chases and patterns? I think it would be pretty awesome. One better would be to retrofit some RGB LED heads into the housing, put in clear lenses and then wham, color mixing in some awesome housing.


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## gafftaper (Sep 19, 2007)

charcoaldabs said:


> P.S.
> Wasn't your school also the one with the special ed puppets hung in a noose in the proscenium wall?



That is correct. As far as I know Timmy and Jimmy are still hanging 20 feet in the air... I couldn't figure out how to get them down safely so I left them. 

There was nothing quite as fun as teaching in a school where you knew there was a good chance that several knives and a gun were possibly in your class room. One day while I was teaching in my theater I suddenly smelled weed. I got to the lobby just in time to see the emergency exit door close. Someone had just stopped in to smoke some pot in the theater lobby. It was an "interesting place". 

Sorry Hijack ends...

I find this discussion of traffic lights oddly fascinating. I've never taken the time to think about them before that much. But it's very intriguing. I eagerly wait for my gaff-brother's answers.


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## gafftapegreenia (Sep 19, 2007)

I have been enjoying this thread as well. No one has has yet come up with the name for the blue-green glass, but here's what I'll give.

The blue-green predates traffic lights. It was first used on the railroads. Why did they need this blue green color? Again, consider illumination sources. (This should help, and I'm not going to say it's proper name -yet- that would give it away)

As most traffic lights are being converted to LED's, the days of lamps, reflectors and glass lenses are drawing to an end. The lense one is tough, but I won't give it till the color question is answered. 

Any thoughts on reflector style?


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## gafftaper (Sep 19, 2007)

So is the glass left over from the lanterns that the switching guys would wave on the railroads... Sorry my railroad knowledge is weak but I have this image in the back of my mind of a man waving a small hand held lantern about the size of an 8" fresnel. Some sort of oil lantern? 

I'm guessing the reflector is some variation of on a Parabolic reflector... it seems like the parallel lines of light coming out of the reflector would be a good thing.


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## gafftapegreenia (Sep 19, 2007)

The reflector is parabolic. So, theres another question down there.

Don't get hung up over the shape of the lens. What's important here is the significance of the blue-green glass in relationship to a non-electric light source.


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## gafftaper (Sep 19, 2007)

Is the Blue Green a form of color temperature correction for a really low color temperature source.


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## gafftapegreenia (Sep 19, 2007)

YES! The yellow flame of a keroscene lantern produces a green light when shown through the blue-green glass. This color is known as signal-green.

As for the lens, there is a specific style of lens that has been recommened by the Institute for Traffic Engineers (ITE - yes there is a group for everything). KOPP calls these "convex, long-range, wide-angle, prismatic traffic roundels".

http://www.koppglass.com/transportationAndSignalLighting.php

Here's the gateway to all things traffic light on the web:

http://signalfan.freeservers.com/


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## Chaos is Born (Sep 19, 2007)

gafftapegreenia said:


> YES! The yellow flame of a keroscene lantern produces a green light when shown through the blue-green glass. This color is known as signal-green.
> As for the lens, there is a specific style of lens that has been recommened by the Institute for Traffic Engineers (ITE - yes there is a group for everything). KOPP calls these "convex, long-range, wide-angle, prismatic traffic roundels".
> http://www.koppglass.com/transportationAndSignalLighting.php
> Here's the gateway to all things traffic light on the web:
> http://signalfan.freeservers.com/



And i actually had just gotten the answer of "signal-green" from my dad... He's an avid train enthusiest so it was just a matter of time before he got back to me...


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## gafftapegreenia (Sep 19, 2007)

Chaos is Born said:


> And i actually had just gotten the answer of "signal-green" from my dad... He's an avid train enthusiest so it was just a matter of time before he got back to me...



I'll believe you. You get the points, but just like Whose Line is it Anyway, they're made up and don't matter.


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## Logos (Sep 19, 2007)

I like traffic lights ... but only when they're green.


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## CLEFFEL (Sep 19, 2007)

Great thread!

Down here some traffic lights have a sort of honeycomb on them so you can only see them when viewed straight on. So the turn lane light can turn green while the others remain red and only the turn lane people can see it.

Maybe Modern Marvels will do a History of the Traffic Light special.

-Chris


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## Chaos is Born (Sep 19, 2007)

gafftapegreenia said:


> I'll believe you. You get the points, but just like Whose Line is it Anyway, they're made up and don't matter.



I was hoping i could buy a cookie with the points! or maybe a custom avatar that looks like a cookie!


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## gafftapegreenia (Sep 19, 2007)

Custom avatars? Sorry, not my call.

Also, check this out, its a "programmable" traffic light. These can be focused on specific lanes of traffic so that drivers do not confuse their light with other lanes. These feature a PAR 36 lamp, as well as a specially designed Fresnel lens. Even more theatrical.

http://signalfan.freeservers.com/traffic signals/3m.htm


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## Les (Sep 19, 2007)

I have a traffic light up in my attic right now. It's unfortunately all-plastic with plastic 8" lenses. The reflectors are indeed parabolic and look like alzak aluminum. I heard that the blue green also works as a color correction in more polluted air. (makes it look more green somehow). Not sure if that's true though. I think that with some refinements they would make great strip lights! I'll bet there are a lot of cities practically giving them away.


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## avkid (Sep 19, 2007)

gafftapegreenia said:


> http://signalfan.freeservers.com/traffic signals/3m.htm


Thanks for that link, I just spent half an hour poring over that site.

Our 1940's Crouse-Hinds control box is still ticking away outside the theatre.


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## Pie4Weebl (Sep 22, 2007)

gafftapegreenia said:


> Custom avatars? Sorry, not my call.
> Also, check this out, its a "programmable" traffic light. These can be focused on specific lanes of traffic so that drivers do not confuse their light with other lanes. These feature a PAR 36 lamp, as well as a specially designed Fresnel lens. Even more theatrical.
> http://signalfan.freeservers.com/traffic signals/3m.htm


agh! I hate those! so hard to see! As much as the focusable lights seem like a good idea if it gets knocked it becomes useless and I like to look at the cross traffic lights to see when the signal is gonna change.

I love this thread though!


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## gafftapegreenia (Sep 23, 2007)

Ok, heres a new question. What kind of lamps are used in incandescent traffic lights?


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## jonhirsh (Sep 23, 2007)

I would say quartz halogen lamp


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## Van (Sep 23, 2007)

gafftapegreenia said:


> Ok, heres a new question. What kind of lamps are used in incandescent traffic lights?


 
That's easy. 

Incandescent Traffic signal lamps.


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## gafftapegreenia (Sep 24, 2007)

Actually, Van, your right. While specs vary, the big manufacturers actually make a traffic signal specific incandescent lamp made for long life and vibration resistance.


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## Logos (Sep 24, 2007)

I like Traffic lights , I like traffic lights, I like traffic lights .... but not when they are red.


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## Charc (Sep 24, 2007)

Logos said:


> I like Traffic lights , I like traffic lights, I like traffic lights .... but not when they are red.



As a new driver (had my license for a couple weeks) I seem to have a hard time with yellow lights. When to go for it, and when to hit the brake. I seem to be doing the wrong thing more often then not.


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## gafftapegreenia (Sep 24, 2007)

In my driver's ed they said that when it was yellow you were always supposed to slow down.


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## jonhirsh (Sep 25, 2007)

Wait you were supposed to pay attention in drivers ed... no wonder 

JH


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## gafftaper (Sep 25, 2007)

Generally the yellow light rule is slow down and stop. However, if your momentum is enough that you would have to slam on the breaks or if stopping would have you wind up in the middle of the intersection then you should continue through the yellow light. If you accelerate to make it through the yellow light in time, you can be ticketed (at least in this state). Learning to judge your momentum as you approach the light is the key. 

When I was in tour bus driver training classes (my grad school summer job), In order to safely stop our 12+ ton vehicle (without throwing our passengers on the floor) they taught us to focus on the crosswalk signals and not wait to be surprised by the yellow light. I've found that it's a trick that really helps my driving in the family car too. If you are approaching a light and you see the crosswalk signal flashing don't walk (or that it has just gone to solid don't walk) you have a much better idea of when the yellow light is coming. That little extra warning time will help you better judge your speed, distance to the intersection and what you should do.


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## propmonkey (Sep 25, 2007)

i usually watch for the cross walk lights.

i remember reading somewhere that they(who knows who "they" are) found that increasing the duration of the yellow light is key in lowering the number of intersection accidents.

when did they begin using yellow lights? i remember seeing traffic lights with just red and green.


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## gafftapegreenia (Sep 25, 2007)

What's really nice are the crosswalk signals with a countdown. They let you know how much time before the light changes.

Some of the more busy intersections also have lights that will show red in all four directions for a couple seconds before the light changes.

I don't know when yellow became mandatory. I do know, however, that the first 3 color signal was invented in 1920 by William Potts of the Detroit Police Department. It used four-inch railroad lenses. (Bonus if you can name the type of lens that would have been) The original signal is actually still in existance and hangs at the Henry Ford Museum in Dearborn, MI.


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## Charc (Sep 26, 2007)

gafftapegreenia said:


> What's really nice are the crosswalk signals with a countdown. They let you know how much time before the light changes.
> Some of the more busy intersections also have lights that will show red in all four directions for a couple seconds before the light changes.
> I don't know when yellow became mandatory. I do know, however, that the first 3 color signal was invented in 1920 by William Potts of the Detroit Police Department. It used four-inch railroad lenses. (Bonus if you can name the type of lens that would have been) The original signal is actually still in existance and hangs at the Henry Ford Museum in Dearborn, MI.



We have all way red here. And our yellow lights are 1/10th the length in seconds of the speed in MPH. I'm not sure if that holds true for other places as well.


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## Van (Sep 26, 2007)

I liked the Lights in Germany. They cycle; Green- yellow- red on the stop cycle, then, red-yellow-green on the start cycle. I was told this is because of the preponderence of vehicles with manual transmissions. The second yellow is a warning to "Put your car in gear" since you're supposed to be in neutral when sitting at a light. 


Oh and BTW I'm really depressed about my answer to the, " what type of lamps do they use in traffic lights" question. I was just trying to be a smartass.


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## gafftaper (Sep 26, 2007)

I love those count down cross walk lights! It tells you if you have enough time to run across the street at the last second. 

Is it just my area or are they messing with the cycle pattern for left turn lanes in your cites too? It used to be that the left turns always went before the general traffic. Now they are messing with the schedule depending on the time of day. If the rush hour is south bound then the southbound general and left turn go at the same time while the north bound waits. Then the northbound general traffic goes with the southbound general. Finally they let the north bound Left turn go. Supposedly it helps improve rush hour traffic. It just confuses me.


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## derekleffew (Sep 26, 2007)

gafftaper said:


> Is it just my area or are they messing with the cycle pattern for left turn lanes in your cites too? It used to be that the left turns always went before the general traffic. Now they are messing with the schedule depending on the time of day. If the rush hour is south bound then the southbound general and left turn go at the same time while the north bound waits. Then the northbound general traffic goes with the southbound general. Finally they let the north bound Left turn go. Supposedly it helps improve rush hour traffic. It just confuses me.



Here in SinCity it's been like that for at least 10 years. One intersection I use twice daily changes depending on time of day. Makes no sense to me as it's 5 miles from the strip, and although two four lane roads, plus left turn lanes, traffic is not that bad there. Very seldom do I have to wait more than one signal change. When I first moved to LV, I thought it was great to have a left turn lane at every intersection. Shortly thereafter I realized how long it adds to the cycle time. See next post.


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## derekleffew (Sep 26, 2007)

*Red light cameras.*

Here red light cameras are illegal, per state legislature, for the purpose of issuing tickets, but the big story the past few days has been North Las Vegas is installing some, for the purpose of "traffic analysis."

While I agree that running red lights is bad, I don't feel computers issuing tickets is the solution. Changing the "yellow means FLOOR IT" mentality will only happen when the _perceived _cycle time is shortened. The joke in LV is "you might as well pitch a tent" if you hit a red light. My commute to work is exactly 5 miles, and can vary from 12-45 minutes depending on traffic and lights.

I've also heard the, possible, urban myth that states that since robotic cameras are always run by a "for profit" outside company, the duration of yellow is shortened in order to "catch" more offenders and issue more tickets, and generate more profit. That's just wrong.


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## derekleffew (Sep 26, 2007)

gafftaper said:


> I love those count down cross walk lights! It tells you if you have enough time to run across the street at the last second.



+1. They should be required at all busy intersections. As a driver, I'd also like to see gates or some other restraint device to keep pedestrians from crossing illegally--a big problem in most tourist locations I suspect. And one of my biggest pet peeves.


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## gafftaper (Sep 26, 2007)

derekleffew said:


> +1. They should be required at all busy intersections. As a driver, I'd also like to see gates or some other restraint device to keep pedestrians from crossing illegally--a big problem in most tourist locations I suspect. And one of my biggest pet peeves.



Dude the Vegas strip cross walk rules are the biggest joke I've ever seen. It seems like there are always 10 people standing in the middle of the street on the median waiting for a break in traffic to run.


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## gafftaper (Sep 26, 2007)

derekleffew said:


> *Red light cameras.*
> Here red light cameras are illegal, per state legislature, for the purpose of issuing tickets, but the big story the past few days has been North Las Vegas is installing some, for the purpose of "traffic analysis."
> While I agree that running red lights is bad, I don't feel computers issuing tickets is the solution. Changing the "yellow means FLOOR IT" mentality will only happen when the _perceived _cycle time is shortened. The joke in LV is "you might as well pitch a tent" if you hit a red light. My commute to work is exactly 5 miles, and can vary from 12-45 minutes depending on traffic and lights.
> I've also heard the, possible, urban myth that states that since robotic cameras are always run by a "for profit" outside company, the duration of yellow is shortened in order to "catch" more offenders and issue more tickets, and generate more profit. That's just wrong.



So here in Seattle we put in four of the automated Red light ticket cameras. This is the story from the paper... "Red-light cameras installed at four Seattle intersections last year have resulted in nearly 14,000 traffic citations and brought in just over $900,000 in revenue." In the suburban city where my college is at they recently put in a couple cameras as well. I swear every time I'm sitting at this one light I see the camera's flash fire off. They are making a killing with those cameras. The real question is does it change people's behavior? If it does then they aren't such a bad idea. But if it only changes people's behavior at that one signal it's just a cash generator.


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## Pie4Weebl (Sep 28, 2007)

one thing some of the traffic lights in st. louis do that I love, at around 11pm on the less heavily used intersections they start flashing orange for the main road and red for the small intersecting road, its a great system which cuts down on those sitting at a red light when there is no other car on the road moments.


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## propmonkey (Sep 29, 2007)

the change some our intersections at night to flashing red. i almost got hit one night. i went through one interesection of all flashing red(i stopped of course) and i assumed the next one was the same but as i quickly found out the other way had only flashing yellow.

why do people not understand that yellow means yield and not go straight through without stopping. if its a yellow and another car is at the intersection, stop and let them go.


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## David Ashton (Oct 17, 2007)

The colours of traffic lights are irrelevant to clour blind people, they just stop when the top light is on and go when the bottom light is on.


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## Van (Oct 17, 2007)

Which is fine 'till you're driving through downtown Tulsa Oklahoma, and they have the lights mounted sideways! Can you believe that? They lay them flat, parallel with the crossbar of the signal post.


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## fosstech (Oct 18, 2007)

Same sideways traffic lights in Cincinnati. I guess it could help with clearance problems.

When I took a trip to Russia five years ago I noticed the traffic light sequence is a little different. When a green light is about to change to yellow, it starts flashing five seconds or so before it changes. Similarly, a red light about to change to green would illuminate the yellow light as well as the red when the opposite set of lights turned yellow.

I could see how the flashing green would be handy for trucks and buses and whatnot, but we would probably still have the same problem of people flooring it once they see that flashing green.


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## gafftaper (Oct 19, 2007)

They've got those flashing green lights up in Vancouver, Canada. They seem to only do it for lights that are intersections of a major street and a quieter side street. The idea being the light is always green with the arterial unless someone's waiting on the side street... in which case there is a flashing green before it turns yellow. 

p.s. Van are the horizontal street lights the source of your anger against Oklahoma?


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## Van (Oct 19, 2007)

gafftaper said:


> ................................................................
> p.s. Van are the horizontal street lights the source of your anger against Oklahoma?


 
Only a minor, minor, minor part.


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## Pie4Weebl (Oct 20, 2007)

well with color blind folk there are that large number who are not all the way color blind and I assume the colors they chose are the best for partially color blind folk.


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## gafftaper (Oct 20, 2007)

My Dad who is color blind was "head tinter" at a paint manufacturing company at one point in his career. It wasn't a big deal because it was all about accurately following a recipe and had nothing to do with visually checking. But it's been a favorite joke in the family for years.


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## Logos (Oct 20, 2007)

I met an LD once who had a real problem in the blue purple range. It is a rare form of colour blindness. He just based decisions in those areas on intensity and frequency specs. I liked his designs.


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## avkid (Oct 21, 2007)

The best non-professional photographer I know is colorblind.
He also does all sorts of digital media creation.
Just thought it was interesting.


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