Talk:Traffic light

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[edit] Uncategorized discussions

I'll give on "light" versus "signal" even if they are synonyms :) Confusion may be created if someone is more used to one versus the other -- perhaps its a regional issue.
Websters notes:
traffic light
A road signal for directing vehicular traffic by means of colored lights, typically red for stop, green for go, and yellow for proceed with caution. Also called stoplight, traffic signal.

--LeFlyman 00:15, 9 Feb 2004 (UTC)

Light synonym for signal? No. What is it when, on my bicycle, I extend my arm? Or a policeman shows me the flat of his hand? Not a light. The correct place to correct confusion on this subject is in the Wikipedia article traffic light, not here.

Psb777 00:47, 9 Feb 2004 (UTC)

Any info/pages on the relationship between traffic signals and mortality? That is, at least where I grew up, I noticed that dangerous intersections and stretches of roads only seemed to get traffic signs/signals when someone was hurt or killed there.

There is a rather controversial section in the MUTCD concerning the criteria for placing a traffic signal but I don't have the time to go find it right now. Does anyone know the section number? --Coolcaesar 21:55, 5 July 2006 (UTC)

As for "traffic light and "traffic signal" being synonyms: Yes, they are. And not only that, but traffic signal *is* the original and more widely used term. You may be more comfortable with hearing "traffic light" in South Africa, but -- if you'd read closely in the wiki article -- the invention of the device was in the US, originally manufactured by the "American Traffic Signal Company."

Further, the external link at the bottom, (http://www33.brinkster.com/iiiii/trfclt) "Inventing history: Garrett Morgan and the traffic signal" links to a page documenting the origins. The term "traffic light" is used 11 times; the term "traffic signal" 50 times! (Yes, I counted -- and I didn't include use of "traffic signalling" or just "signal.")

Here's more: A search of Google for the terms "bicycle traffic signal" (as per your question) produces as the first link: (http://www.johnforester.com/Articles/Facilities/traffsig.htm) discussing traffic signals for bicycles -- and no, not the kind with your arm. "Traffic light" is not mentioned once. "Traffic signal" or just "signal" is used througout. Please try to find a usage of "traffic signal" to refer to anything other than what you call a "traffic light."

FYI: When you extend your arm, you are making a hand signal; you aren't making a traffic signal.

LeFlyman 22:06, 9 Feb 2004 (UTC)

I was surprised to read here that traffic lights are often synchronized to allow a driver to hit several greens in a row. I remember reading that normally they were designed to operate the opposite way so as to prevent people from driving too fast in urban areas. I will attempt to research this. Anyone have anything to say on this topic? Not sure if I'm adding too many peculiarities to this article but I suppose someone else will take them out if they feel that way about my edits. Jarsyl 09:47, 2004 Aug 5 (UTC)

In Warsaw, Poland, traffic lights are sometimes synchronized in such a way that if you drive 50 or 60km/h you hit several greens in a row, driving 10km or more without stopping, but when you drive faster, you have to stop on every red. In Kraków, Poland, which is in my opinion an absolutely great idea, there are signs displaying how fast exactly you have to drive to hit the next green light, which is usually way below 60km/h, so even in heavy traffic everyone keeps going. Rafał Pocztarski 17:28, 5 Aug 2004 (UTC)

In New York City, lights on many of the one-way avenues are timed so that a car traveling at 30mph will hit only green lights for the length of the avenue. This keeps traffic slowed down to the speed limit, since any cars going faster than the limit will hit a red light and have to wait. It can be exhiliarating to "surf" the "wave" of green lights, to travel all the way down the island without stopping once. The hazard in this is that cars tend to bunch up at the front of the "wave", so any pedestrians caught in the crosswalk as the light changes will risk being bowled over by dozens of cars at full speed. By contrast, in Boston I've seen signs which say "Lights Timed to Require Frequent Stops". This doesn't seem to make traffic much calmer, since drivers end up speeding as fast as they can between the lights to try to avoid the reds. Also, the lights sometimes cause traffic to back up to the previous intersection... making it more like "Lights Timed to Cause Major Gridlock and Traffic Snarls". ~Anonymous 17:36, 21 Jun 2005 (UTC)

In Silicon Valley, several major roads have synchronized lights, including 10th and 11th Streets in San Jose and certain segments of the Santa Clara County expressway system. They are designed so that if you stay at the speed limit, you should be able to get 7 or 8 green lights in a row.

I have also seen traffic lights on Sunset Boulevard in Los Angeles that are designed to cut down on speeding by turning red (even if no cross-traffic is waiting to cross or to turn onto Sunset) if you approach them too fast. --Coolcaesar 21:52, 21 Jun 2005 (UTC)

[edit] Garrett Morgan's signal

I'd be interested to see more detail on the subject of why Garrett A. Morgan is wrongly credited with invention of the traffic signal. The U.S. Dept. of Transportation site states that Morgan was the first to patent it, while being quite vague on the issue that earlier inventors had "experimented with and even marketed" signals. An about.com article is more specific, saying that while earlier inventors had indeed patented traffic signals, Morgan's was the first that could be inexpensively produced: "In addition, my invention contemplates the provision of a signal which may be readily and cheaply manufactured"; this provision is not mentioned on the myth-debunking site. The corresponding section in our Garrett Morgan article appears to be lifted almost verbatim from the about.com article, but also fails to mention inexpensive manufacture. Even if we don't know the reason for wrong attribution, I think the phrase "for unknown reasons" should be removed; someone knows the reasons, even if it's not us. -- Wapcaplet 19:33, 12 Nov 2004 (UTC)

  • I agree with this and have removed "For unknown reasons" from the article, since no one has (yet) come up with a reason to keep them. CheekyMonkey 13:43, 10 Dec 2004 (UTC)

[edit] History

The first three colour traffic light was erected in 1916 in New York City (URL: http://www.ci.nyc.ny.us/html/nypd/html/transportation/newpage5.html), not in 1920 in Detroit, what was said in the article. rozziite 08:00, 27 June 2006 (UTC)

Even the article you cited confirms that was not the precursor to the modern traffic light. Lights only faced north and south and the meaning of the colors were completely different from today's standard interpretation. -- KelleyCook 14:16, 27 June 2006 (UTC)

Is there anything about an african-american called Garret A. Morgan? I recently read an article giving him the credit for traffic lights invention.

[edit] A little too many East Berlin photos?

Don't you think there are a little too many East Berlin photos? The segment is pretty short, and the whopping three images extend way into the next section. I'd suggest putting the image from Barnes Dance instead of one of the East Berlin ones, as it would go great with the "Pedestrian Scramble" section. newkai 13:40, 18 Jun 2005 (UTC)

[edit] What kind of bulbs?

I don't believe this article specifies what kind of light bulbs that modern signals use, i.e. how come you don't see them burning out often.

Just added a section on the shift from incandescent bulbs to LEDs. Probably could use more meat; as well as more information on how incandescent bulb technology works. The color filters used to produce red/green/yellow from white light are discussed elsewhere in the article; as are the "stencil" filters used to produce arrows or other shapes. One other thing that isn't mentioned, but is worth a mention, are the various filters (metal "blinder" apertures, polarizing filters) used to limit the angle of visibilty of a light--for example, to make a left-turn signal (in the US) difficult to view from the straight-ahead lanes. (Though it should be noted that the polarizing filters are being phased out--at least where I live--that might be due to the LED transition).

I think it might be useful to re-organize the page, so the technical aspects (how traffic lights work) is in a separate section from the application.

One other section I'd like to add is one on legal issues--what constitutes a red light violation (different jurisdictions have different laws), enforcement aspects (different jurisdictions are stricter than others; in some places red lights are routinely ignored by motorists), and a mention of red light cameras.

EngineerScotty 03:09, 27 July 2005 (UTC)

[edit] Lead Light

Where do they call it that? I've never heard the term and I've lived in nine states. BrownstoneKnockn 15:47, 1 December 2005 (UTC)

I concur with your question. I've never seen that term on the West Coast — and I've read Gary Richards' newspaper column on Silicon Valley road construction issues, Roadshow, regularly for almost two decades. What state uses "lead light" terminology? This may be a regional issue, in which case the "lead light" statement needs to be qualified and limited accordingly.--Coolcaesar 17:24, 1 December 2005 (UTC)

I have taught classes on traffic signal design and operation all over the U.S., and have never heard the term "lead light". But I suspect anyone committed to the use of "light" instead of "signal" might be hard-pressed to give it up. The correct term in the U.S. is "leading left turn". I know the original author was not yet intending to distinguish between left and right turns, but this term demands that distinction given its use in the U.S. And "leading left" means that the turn signal precedes (not proceeds) the opposing through movement, while a lagging left follows the opposing through movement. The arrangement of movements into pair of left turns and their opposite through movements to provide four conflicting pairs is a direct construct of phase-based signal logic used in the U.S. I have not attempted to write about phases, but I have corrected the leading turn discussion.Rick Denney 05:14, 16 January 2006 (UTC)

[edit] Colours of clothing to indicate sexual availability in US

The other uses section includes the claim In some areas of the US, patrons of various social gatherings use traffic light color coding to indicate availability: red clothing would indicate that the wearer was in a monogamous relationship, amber would indicate a nonmonogamous relationship, and green would indicate that the wearer was single. To my British mindset this sound very unlikely and seems to be lacking any specific detail to qualify it for encylopedic inclusion. Could anyone clarify this?

I have never heard of this anywhere on the West Coast. This may be a weird regional practice occurring in some obscure corner of the Midwest, the Great Plains, or the East Coast, but I doubt it. I suspect that it is misinformation planted by a troll and should be removed. --Coolcaesar 01:57, 11 December 2005 (UTC)
Actually, I can confirm this practice. I've certainly seen "Traffic light discos" advertised at several UK universities. Not convinced it merits inclusion in an encyclopedia entry though so I snipped it. --Richard Clegg 15:41, 11 December 2005 (UTC)

That's UK universities though. It's hardly a cultural phenominon. You can also get traffic light lollypops where I live but there's no point mentioning that is there? [Gareth Parr]


[edit] Pike Place Market

I think that the intersection of First and Pike and in Seattle (in front of Pike Place Market) is a pedestrian scramble, perhaps the only one in the city. Can anybody confirm this? Brianhe 06:11, 11 January 2006 (UTC)

[edit] Traffic Light Configurations

It might be useful to add typical light configurations that vary by area. For example (with both cases having exceptions), typical New Jersey lights are in yellow stoplights mounted on silver polls, while typical New York lights are in green cases on cables. Or in Washington, D.C., lights are often vertical and do not even cross above the street. This is somewhat mentioned in the article, but in general, for example, the NY/NJ rule holds true, and it might be somewhat useful //MrD9 08:48, 13 February 2006 (UTC)

I'm not sure. It sounds interesting, but on the other hand, it may grow into a very large list. For example, most California cities have black stoplights mounted on silver-colored poles, but there are numerous exceptions. There is also the additional issue of how we would have to first decide on the features worth noting — dedicated lights for turning across opposing traffic, use of a border on the backplate for visibility, sensor loops, separate signals for pedestrians, etc. I've noticed that many European countries use a border on the backplate. Last time I checked, USDOT is still investigating whether to allow that in the U.S. (since there is a good counterargument that such borders only increase the severe visual clutter already typical of American streets).
I'm sure there must be literally hundreds of variations across the world. Anyway, I suppose it can always be separated into a separate article on "Traffic light usages by jurisdiction" if it gets too big. --Coolcaesar 17:05, 13 February 2006 (UTC)

Well, I guess I failed to mention this exactly how I had meant to, but I meant sort of like either major characteristics or major differences between places. For example, I noticed that in Virginia there are a lot of signs that say something about yielding on a solid green light when making a left turn--these were confusing because they made it seem as if this was not the norm in VA and that normally one making a left turn would do something other than yield to oncomming traffic when making the left. In other words, these signs were weird in that they confused everyone I was with into feeling like we were doing something wrong even thoguh we weren't--there were just unnecessary signs. (Or at least that is what we concluded--If left turn traffic rules are actually different in Virginia, then we totally missed that.)

Or to add to my NY/NJ list (I love how it's always "New York/New Jersey/(Connecticut)" order, even from native (northern) NJians), in northern NJ, many roads have been built around stuff that was already there--therefore, they are narrower than they would be if everything were being rebuilt today. Therefore, when a single-lane road broadens into 2-3 lanes at an intersection (commonly 2, with one straight/right and one left lane OR one straight/left and one right lane), there is usally a sign on the right side of the raod that shows the lanes and which ways traffic in each lane are allowed to go--in NY and VA, however, from my experience, on larger roads, these signs are not often on the right, they are often hanging from the wire/pole that supports the stoplights and are placed above (not to the right side of the street) the lanes themselves.

Again, I simply wanted to mention some potential ideas to add to this article or to add to spin off articles, and obviously none of them have to be implemented in any way. I just thought that others might be mildly interested in the various ways certain areas usually set up/cconstruct intersections and traffic lights around the world. //MrD9 21:51, 13 February 2006 (UTC)

Well, if you think that's confusing, we have a very odd situation here in California. In some suburban cities, left turns on arterials are normally from dedicated lanes, so that left turns against opposing traffic are an exception authorized by the signs you just mentioned. In many rural and inner-city areas, left turns against opposing traffic are the norm and dedicated left-turn lanes are rare.
As for lane direction signs, I've seen them mounted on both overhead and on the roadside on both state highways and in cities.
However, I'm not sure if the matters you raised are appropriate for this encyclopedia article, as they are general traffic control or intersection design issues. They're actually tangents from the main topic of this article, which is traffic lights. When I think of traffic lights, I'm thinking of the actual lights, the poles and wires that support them, and their orientation, number, and colors. Remember, the advantage of hypertext wikis is that one can create a different article for each particular topic and cross-link to other relevant topics. What does everyone else think? --Coolcaesar 01:42, 15 February 2006 (UTC)

I agree with you that it's way too much for this article. Upon reskimming parts of the article, inlcuding the mounting section, though, it appears that this (and possibly other) sections could potentially be extended a bit more regarding color, potentially something with dedicated left (or right) turn lights, and even an expansion of "here are significant differences from place to place in how traffic lights are mounted or positioned so that they are visible to drivers" to include something regarding the issues in "Traffic signals in most areas of Europe are located at the stop line on same side of the intersection as the approaching traffic and are often mounted overhead as well as on the right and left sides of the road" but regarding the US (or other areas of the world)--around here, at least, it's typical for drivers to practically pull up to the middle of the intersection (obviously, exaggeration, but they definately overshoot the stopping lines that are on the rora'd surface by often a meter or two depending), and apparently in Europe (as the sentence after the one I just quoted states) that's hard, because then you can not see the lights.

If I have time, I might research some more on regional differences or similiarities (because even if it does not go here, I want to know for my own sake), and if i find anything that might be noteworty or mentionable in this or a similar article, I'll either add it or bring it up here again. Thanks for your discussion. //MrD9 02:07, 15 February 2006 (UTC)

World-wide traffic signals and ops vary widely by culture. Athens, Greece has quite a few "Stop Bar Shoulder Mounted" signals. Common frequent practice is for the lead drivers to pull up as far into the intersection as they can, often in front of those shoulder signals. As soon as the light turns green, everyone hits their horn so the ones in front know to go. It is NOT road rage.

Conversely, one of my Greek students told me how during his first trip to the USA, he automatically continued his habit of hitting the horn--he almost got his "b__t" whipped by some locals who took a dim view of his helpfulness.

In the late eighties I visited Alexandria and Cairo Egypt. Egyptian practice at the time meant once a light turned red, everyone continues to run it until opposing side street "green" traffic asserts their dominance. At that point, the stopped traffic "swarms"--each driver tries to manuver around the leading stopped cars for better starting position.

Egyptian enforcement was unique also. Young boys appearing age 10 and up live in central road camps. Each morning they load into busses, dressed in a uniform shirt, sometimes a cap, often bare foot, and equipted with a lunch pail, notebook and pencil. They are dropped at key intersections throughout the city where they spend the day observing drivers and recording tag numbers and offenses of drivers. I was told these notebooks are collected, coalated, and owners have to settle their fines when they renew their annual registration. Again, very wierd in the eyes of a Westerner.

Perhaps the main article here could concentrate on the actual signals themselves. Indication configurations, sizes, colors, sequence variations, temporary signals, history, oddities, etc. Branch off related pages dealing with mounting variations and hardware, enforcement methods, timing and coordination, detection methods, controller cabinet standards and designs, storm damage design issues, probably others as well... Possibly try to group standards of each country together instead of mix and match. Cite the MUTCD and/or state DOT reference with YEAR of issue. Other countries also as applicable. For instance the current MUTCD prohibits the "Red Indication + White Strobe" variant mentioned in the article. If the MUTCD version [year] was cited, such a reference would remain true in context. [btw- Alabama STILL uses those on rural highways as a single indication between the two normal heads.] --Steve 22:44, 29 March 2006 (UTC)

[edit] Tianjin China

A sentence in this part of the article just seems pointless to me.

   "The major disadvantage of this system of traffic light is... as well is being problematic for the color blind."

Problematic for the color blind? Wouldn't the REGULAR traffic light system be "problematic to the color blind" too? Unless someone sees the point in this sentence I'm removing it. 4.231.41.233 14:09, 1 June 2006 (UTC)

A regular light as red/amber/green from top to bottom or left to right, thus a colorblind person can tell which one is on, by which one is lit up. -newkai | talk | contribs 15:09, 1 June 2006 (UTC)

[edit] Yukon reference

Regarding the sentence

    "Yukon Territory signals, currently found only in Whitehorse, are mounted horizontally over the road, and additional signals facing the same direction are sometimes also mounted vertically on the vertical post that supports signal mounts."

Unless I am reading the sentence wrong, traffic lights mounted horizontally over the road as well as vertically on the support post at the same intersection can be found everywhere, not just the Yukon territory! In fact, some of the vertical lights are actually mounted on top of the vertical post to be seen at a distance, especially if the intersection is at the bottom of a hill. --Goldrushcavi 19:10, 10 June 2006 (UTC)

[edit] Moved

I moved this section of the article here.

[edit] Lloydminster situation is actually quite common

The Lloydminster situation is actually quite common in the United States as well. We have many traffic lights at intersections on city boundaries that often correspond with boundaries between cities, counties, and states. In fact the situation is even more complicated legally in the United States since in the U.S. the states are the plenary sovereigns! We got rid of the monarch a long time ago. If no one objects, I'm going to generalize that paragraph to take a worldwide view. --Coolcaesar 20:52, 21 October 2006 (UTC)

Having added it myself (and driven through that intersection), I cited it as an example. I don't doubt that there are cases in the US such as Texarkana and Kansas City. Do you have examples where a state boundary follows a roadway through a controlled intersection? GBC 23:13, 21 November 2006 (UTC)

[edit] Traffic "signal" or Traffic "light"

Signal seems to be the communicative term; in legalese, it's a "traffic control device".

When the city proposed to put up lighting along our street for nighttime illumination, they called them "traffic lights" on the official notice about a local improvement charge on our property taxes. Up to then, I thought "traffic lights" were the red-yellow-green control lights, but municipal parlance probably called them "traffic signals". GBC 23:19, 21 November 2006 (UTC)

See wiktionary:traffic light. That shows "traffic signal" to be a US variation of a term. Dictionary.com shows "traffic light" as the entry term, too (traffic signal redirects to traffic light). Within the article, as long as the two terms are defined in the beginning, I don't see why they can't be interchangeable. --MPD01605 (T / C) 23:27, 21 November 2006 (UTC)

[edit] Introduction needs rewriting

The following sentences are completely incomprehensible. I would rewrite them myself if I knew anything about the subject matter.

A turn light preceding the opposing through movement is called a leading left turn in the U.S., because it leads the opposing through green light (likewise, in the U.S., a left turn arrow that follows the opposing through movement is known as a "lagging left turn"). In Canada, a turn that is authorized before the opposing traffic, OR with an early left turn light is activated on the opposing side is called an Advanced Green. An advanced green can either mean that the traffic on your side could be going through and turning left before the opposing side sees a green. Or it could also mean both sides of traffic have an advanced turn green.

Nomist 12:33, 10 December 2006 (UTC)

I understand what it's saying (well, the first half), but yeah if you don't know what's going on, it's...yeah.
A "leading left turn" in Virginia. In this case, left turns in each direction are permitted before straight traffic.
Enlarge
A "leading left turn" in Virginia. In this case, left turns in each direction are permitted before straight traffic.
In the United States, high-traffic intersections often have a dedicated left turn lane with its own dedicated signal. In such lights, the green circle is replaced with a left-pointing arrow (usually done by a filter, but LED traffic lights have made it possible to make an arrow). This is called a protected left turn because when left-turn traffic has the green light, the opposing traffic (whose path the left-turn vehicles must cross) has a red light. After cross-traffic is given the green light, the cycle begins. When left-turn traffic is permitted to go before the opposing traffic, it is called a "leading left turn"; when left-turn traffic is permitted to go after the opposing traffic, but before the cross traffic, it is called a "lagging left turn".
I dont know the whole Canada deal. I happen to have a picture of a leading left turn. I can crop it if you want (Just how much should I crop?). Hopefully, this clears things up a little bit. --MPD01605 (T / C) 18:31, 10 December 2006 (UTC)
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