# How are new traffic signals introduced? **URL:** \ **Category:** Factual Questions\ **Created:** [September 21, 2015, 4:48pm UTC](https://boards.straightdope.com/t/how-are-new-traffic-signals-introduced/732127 "2015-09-21T16:48:53Z")\ **Posts on this page:** 18\ **Page:** 1
**Author:** ![iceiso](https://avatars.discourse-cdn.com/v4/letter/i/3be4f8/32.png) [@iceiso](https://boards.straightdope.com/u/iceiso)\ **Post date:** [September 21, 2015, 4:48pm UTC](https://boards.straightdope.com/t/how-are-new-traffic-signals-introduced/732127/1 "2015-09-21T16:48:53Z")
I was listening to the radio this morning and they were reporting on local roadwork. They said to pay attention to the “red X’s and green arrows” on a certain busy road, since they’ve recently changed. This got me thinking… 1. I travel often to different rural areas where traffic signals are less numerous than what you find in big cities. Therefore, people from a rural area generally will not be familiar with certain traffic signals found in the cities. 2. At some point in every traffic signal’s life, it was new and had to be “rolled out” (ie. the first time the “No U-turn” sign was ever used was MM, YYYY) 3. Likewise, for every driver, there was the first time he/she had seen any given signal while driving (ie. the first time I saw a stop sign while driving was when I drove my dad’s car in my high school parking lot). If there was a need to roll out a new traffic signal now, how would it be done? Does it have to be introduced over the course of many years, starting with driver’s ed literature? Does the federal/state/local transportation authorities issue a letter? An e-mail? Or, is it just thrown out there? Likewise, how was it done in the past, say, 30 years ago? ---
**Author:** ![slash2k](https://avatars.discourse-cdn.com/v4/letter/s/439d5e/32.png) [@slash2k](https://boards.straightdope.com/u/slash2k)\ **Post date:** [September 21, 2015, 5:50pm UTC](https://boards.straightdope.com/t/how-are-new-traffic-signals-introduced/732127/2 "2015-09-21T17:50:57Z")
Probably the best example I can think of is the introduction of [roundabouts](https://en.wikipedia.org/wiki/Roundabout) in my locale, which has happened over the last 15 years or so. When the first one was nearing completion, the highway department had a public relations campaign, with for example articles in the newspaper on how to navigate them and who had the right of way, and what the sign looks like to denote one. These articles started appearing maybe a month or so before it opened, and continued sporadically as the second/third were constructed. Now they’re old hat. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [September 21, 2015, 5:53pm UTC](https://boards.straightdope.com/t/how-are-new-traffic-signals-introduced/732127/3 "2015-09-21T17:53:34Z")
I’d be surprised if there’s any master plan. From what I’ve seen, new types of signals are simply installed, sometimes with some signage to explain what they mean. Recently, a particular intersection got a flashing yellow left-turn arrow. It took me awhile to realize that it meant “unprotected left-turn OK.” As an aside, I recently had a business trip to Vancouver, Canada. They have flashing green lights at some intersections, and everyone else was treating them as regular green lights. I asked someone what they meant, and they just shrugged - something having to do with cross-walks. ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [September 21, 2015, 6:00pm UTC](https://boards.straightdope.com/t/how-are-new-traffic-signals-introduced/732127/4 "2015-09-21T18:00:46Z")
> [@beowulff](#): > > As an aside, I recently had a business trip to Vancouver, Canada. They have flashing green lights at some intersections, and everyone else was treating them as regular green lights. I asked someone what they meant, and they just shrugged - something having to do with cross-walks. If those people were drivers they should have their license suspended. If they were pedestrians their ignorance is putting their lives in danger. A flashing green is an advanced green permitting left turns while the opposite side is still red. Pedestrians who don’t know this are liable to be flattened by left-turning traffic. Most intersections now use a separate light with a left green arrow but the flashing green is still around. ---
**Author:** ![Diceman](https://avatars.discourse-cdn.com/v4/letter/d/22d042/32.png) [@Diceman](https://boards.straightdope.com/u/Diceman)\ **Post date:** [September 21, 2015, 6:01pm UTC](https://boards.straightdope.com/t/how-are-new-traffic-signals-introduced/732127/5 "2015-09-21T18:01:50Z")
> [@slash2k](#): > > Probably the best example I can think of is the introduction of [roundabouts](https://en.wikipedia.org/wiki/Roundabout) in my locale, which has happened over the last 15 years or so. When the first one was nearing completion, the highway department had a public relations campaign, with for example articles in the newspaper on how to navigate them and who had the right of way, and what the sign looks like to denote one. These articles started appearing maybe a month or so before it opened, and continued sporadically as the second/third were constructed. Now they’re old hat. On the other end of the spectrum, around here they’ve been changing when the left-turn signal appears on traffic lights (formerly it appeared after the green “go” period, now it comes before that.) Implementation has been sporadic and poorly-communicated. An intersection will just change one day, with no rhyme or reason apparent. The result has been a huge surge in people making left turns at the wrong time. The only reason there hasn’t been a huge surge in accidents is because most of us are now quite wary of left-turners, for exactly this reason. ---
**Author:** ![Bill\_Door](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@Bill\_Door](https://boards.straightdope.com/u/Bill_Door)\ **Post date:** [September 21, 2015, 6:52pm UTC](https://boards.straightdope.com/t/how-are-new-traffic-signals-introduced/732127/6 "2015-09-21T18:52:59Z")
> [@wolfpup](#): > > If those people were drivers they should have their license suspended. If they were pedestrians their ignorance is putting their lives in danger. > > A flashing green is an advanced green permitting left turns while the opposite side is still red. Pedestrians who don’t know this are liable to be flattened by left-turning traffic. Most intersections now use a separate light with a left green arrow but the flashing green is still around. [DriveSmartBC](http://drivesmartbc.ca/signs-signals/flashing-traffic-signals) claims that: A driver facing a flashing green light must approach so that they are able to stop, should a stop be necessary, before reaching the crosswalk or the signal as the case may be. They must then yield to pedestrians, again in the manner specified for a flashing red light. Pedestrians may cross at both types of signals in the same manner as at a flashing red light. Mentioning nothing about left turns. ---
**Author:** ![suranyi](https://avatars.discourse-cdn.com/v4/letter/s/e36b37/32.png) [@suranyi](https://boards.straightdope.com/u/suranyi)\ **Post date:** [September 21, 2015, 7:00pm UTC](https://boards.straightdope.com/t/how-are-new-traffic-signals-introduced/732127/7 "2015-09-21T19:00:13Z")
In some cases I know, a warning sign is placed at the intersection a few weeks before the traffic signal is turned on. It says something like: “New signal at this intersection starting soon.” ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [September 21, 2015, 7:16pm UTC](https://boards.straightdope.com/t/how-are-new-traffic-signals-introduced/732127/8 "2015-09-21T19:16:03Z")
> [@Bill\_Door](#): > > [DriveSmartBC](http://drivesmartbc.ca/signs-signals/flashing-traffic-signals) claims that: > > A driver facing a flashing green light must approach so that they are able to stop, should a stop be necessary, before reaching the crosswalk or the signal as the case may be. They must then yield to pedestrians, again in the manner specified for a flashing red light. > > Pedestrians may cross at both types of signals in the same manner as at a flashing red light. > > Mentioning nothing about left turns. Quite correct, thank you. It just reinforces my belief that BC isn’t really part of Canada! 😃 [Why B.C.'s flashing green lights don’t mean the same thing as those in Ontario](http://www.theglobeandmail.com/globe-drive/culture/commuting/why-bcs-flashing-green-lights-dont-mean-the-same-thing-as-those-in-ontario/article25066266/) In Alberta, Ontario, Quebec, New Brunswick, Nova Scotia, Northwest Territories and Nunavut, the driving manuals say a flashing green light means the same thing as a left-pointing arrow and a green light: it’s an advance green. Oncoming traffic is still facing a red. You may turn left, go straight ahead or turn right. ---
**Author:** ![slash2k](https://avatars.discourse-cdn.com/v4/letter/s/439d5e/32.png) [@slash2k](https://boards.straightdope.com/u/slash2k)\ **Post date:** [September 21, 2015, 8:46pm UTC](https://boards.straightdope.com/t/how-are-new-traffic-signals-introduced/732127/9 "2015-09-21T20:46:26Z")
> [@Diceman](#): > > On the other end of the spectrum, around here they’ve been changing when the left-turn signal appears on traffic lights (formerly it appeared after the green “go” period, now it comes before that.) Implementation has been sporadic and poorly-communicated. An intersection will just change one day, with no rhyme or reason apparent. The result has been a huge surge in people making left turns at the wrong time. The only reason there hasn’t been a huge surge in accidents is because most of us are now quite wary of left-turners, for exactly this reason. Move to Topeka, Kansas. Around here, at some intersections the left-turn arrow can appear before or after, depending on traffic patterns, and it can change even from one cycle to the next. [From the Topeka Capital-Journal](http://cjonline.com/news/2012-04-11/green-light-tunnel-includes-drop-crashes): > [@](#): > > She added: “As part of this system you may have noticed what traffic engineers call ‘lead/lag’ left turn phasing. At the locations that have protected only left turn phasing (you can turn only on a green arrow) you may receive the arrow at the beginning of the thru traffic phase (lead) or at the end of the thru traffic phase (lag). This is done to improve capacity.” > > Voss said the lead/lag traffic signals use the information they collect to “decide” whether through traffic gets to go first or left-turn traffic gets to go first. ---
**Author:** ![Mr\_Downtown](https://avatars.discourse-cdn.com/v4/letter/m/8e8cbc/32.png) [@Mr\_Downtown](https://boards.straightdope.com/u/Mr_Downtown)\ **Post date:** [September 22, 2015, 3:38am UTC](https://boards.straightdope.com/t/how-are-new-traffic-signals-introduced/732127/10 "2015-09-22T03:38:55Z")
In many states, the flashing yellow left-turn arrow is just now being introduced (a phase during which left turns are permitted but not protected). The meaning is given on a small sign hanging next to the signals I’ve seen in Texas. I suppose a generation from now, when everyone knows what they mean the signs might go away. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [September 22, 2015, 5:55am UTC](https://boards.straightdope.com/t/how-are-new-traffic-signals-introduced/732127/11 "2015-09-22T05:55:01Z")
> [@Mr\_Downtown](#): > > In many states, the flashing yellow left-turn arrow is just now being introduced (a phase during which left turns are permitted but not protected). The meaning is given on a small sign hanging next to the signals I’ve seen in Texas. I suppose a generation from now, when everyone knows what they mean the signs might go away. I saw these while visiting Medford Oregon a few years ago (and it just so happened that I had read about them on-line somewhere just a few weeks before that). I have not seen this in California yet. [_Doghouse-style_ signals](http://img05.deviantart.net/f07e/i/2015/052/b/f/incandescent_siemens_doghouse_traffic_light_by_2001_acsiren-d8j0b3r.jpg) are very common here (ETA: including the explanatory sign), but apparently (I read) they are considered un-good and are to be phased out. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [September 22, 2015, 6:01am UTC](https://boards.straightdope.com/t/how-are-new-traffic-signals-introduced/732127/12 "2015-09-22T06:01:58Z")
The first time I encountered a left-pointing red arrow was in Oregon, many years ago, and I didn’t know what it meant. (But I made a good guess that happened to be correct.) In California at the time, left-turn-only lanes were controlled by a signal that had a green left-arrow (which meant protected left-turn), a solid yellow light, and a solid red light. The yellow and red lights for the left turn lane were not arrow-shaped as they are now. California was also behind the other states, around that same time, in the pavement markings for a two-way left turn lane. Again, I had read about the new markings somewhere, but the first time I ever saw them was in far northern California (as I was driving up to Oregon) and then in Oregon. Before long, the new markings were all over California. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [September 22, 2015, 6:04am UTC](https://boards.straightdope.com/t/how-are-new-traffic-signals-introduced/732127/13 "2015-09-22T06:04:12Z")
The first time I ever encountered a _right-pointing_ red arrow (right here in California this time), I didn’t know what it meant. I guessed (wrong this time) that it meant full stop then proceed with the right turn when safe. It actually means NO RIGHT TURN NEVER NO-HOW NO-WAY while the red right-arrow is displayed. ---
**Author:** ![Isilder](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@Isilder](https://boards.straightdope.com/u/Isilder)\ **Post date:** [September 22, 2015, 2:38pm UTC](https://boards.straightdope.com/t/how-are-new-traffic-signals-introduced/732127/14 "2015-09-22T14:38:39Z")
> [@wolfpup](#): > > If those people were drivers they should have their license suspended. If they were pedestrians their ignorance is putting their lives in danger. > > A flashing green is an advanced green permitting left turns while the opposite side is still red. Pedestrians who don’t know this are liable to be flattened by left-turning traffic. Most intersections now use a separate light with a left green arrow but the flashing green is still around. Terrible to have flashing green. People might misunderstand the flashing ,eg they may be blinking and think it was just their blinking doing it. I don’t mind flashing orange or flashing red, because they both say “warning”, and if you don’t notice them flashing, then you think they are solidly on , and that only turns them to “stop !” rather than “GO”…they “fail safe”… Also, the railway crossing seem to have flashing red lights… and these may be taken to mean “don’t crash into this pole!”. perhaps rail crossings should have regular red orange green traffic lights… so the red light is solid, and drivers more quickly/easily see its a traffic light… ---
**Author:** ![Diceman](https://avatars.discourse-cdn.com/v4/letter/d/22d042/32.png) [@Diceman](https://boards.straightdope.com/u/Diceman)\ **Post date:** [September 22, 2015, 4:30pm UTC](https://boards.straightdope.com/t/how-are-new-traffic-signals-introduced/732127/15 "2015-09-22T16:30:53Z")
> [@slash2k](#): > > Move to Topeka, Kansas. Around here, at some intersections the left-turn arrow can appear before or after, depending on traffic patterns, and it can change even from one cycle to the next. [From the Topeka Capital-Journal](http://cjonline.com/news/2012-04-11/green-light-tunnel-includes-drop-crashes): OK, that’s just fucking evil. Whoever designed that system needs to be euthanized. Or at least, forceably removed to some remote wilderness location 100 miles away from the nearest traffic light. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [September 22, 2015, 5:29pm UTC](https://boards.straightdope.com/t/how-are-new-traffic-signals-introduced/732127/16 "2015-09-22T17:29:45Z")
> [@Diceman](#): > > OK, that’s just fucking evil. Whoever designed that system needs to be euthanized. Or at least, forceably removed to some remote wilderness location 100 miles away from the nearest traffic light. Nah. Just make him stand out in the middle of a busy example of those intersections. He’ll be crushed between two colliding confused cars soon enough. A fitting end if ever there was one. ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [September 22, 2015, 6:19pm UTC](https://boards.straightdope.com/t/how-are-new-traffic-signals-introduced/732127/17 "2015-09-22T18:19:06Z")
> [@wolfpup](#): > > If those people were drivers they should have their license suspended. If they were pedestrians their ignorance is putting their lives in danger. > > A flashing green is an advanced green permitting left turns while the opposite side is still red. Pedestrians who don’t know this are liable to be flattened by left-turning traffic. Most intersections now use a separate light with a left green arrow but the flashing green is still around. False. That’s what it means in Quebec and perhaps some other places. In Vancouver, a taxi driver explained to me that they were normally green but flashed to indicate that a pedestrian has pressed the crossing button and they would soon turn red. I like the system in Quebec, but it is not universal. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [September 22, 2015, 8:32pm UTC](https://boards.straightdope.com/t/how-are-new-traffic-signals-introduced/732127/18 "2015-09-22T20:32:11Z")
> [@wolfpup](#): > > Quite correct, thank you. It just reinforces my belief that BC isn’t really part of Canada! 😃 > > [Why B.C.'s flashing green lights don’t mean the same thing as those in Ontario](http://www.theglobeandmail.com/globe-drive/culture/commuting/why-bcs-flashing-green-lights-dont-mean-the-same-thing-as-those-in-ontario/article25066266/) > In Alberta, Ontario, Quebec, New Brunswick, Nova Scotia, Northwest Territories and Nunavut, the driving manuals say a flashing green light means the same thing as a left-pointing arrow and a green light: it’s an advance green. Oncoming traffic is still facing a red. You may turn left, go straight ahead or turn right. Here in Massachusetts we still have leftover flashing green lights. No one knows what they mean, although occasionally a newspaper story will pop up to remind people, after which they will forget again. I’ve pointed this out before on this Board. It does NOT mean an advance green for one direction, as in Canada. According to Wikipedia, here’ s what flashing greens mean in various places: > [@](#): > > Flashing green light[edit] > > In British Columbia,[21] a flashing green globe signal is used at a pedestrian crossing or intersection, at which pedestrians have the ability to stop traffic to allow a safe crossing. They may also be used at a drawbridge. The flashing green indicates that the signal is not currently in use. After the pedestrian pushes the button to trigger the signal, the light becomes a steady green until the sequence of yellow, then red (at which time the pedestrian crossing gives a walk signal) as in a conventional set of traffic lights, then returns to flashing green until another crossing is requested.[22] > > In Ontario, a flashing green indicates a protected “advance green” during which traffic may proceed straight through the intersection or turn left or right, as allowed at any particular junction and from the proper lane; opposing and cross traffic have a red signal.[23] Ontario’s flashing green signals have largely been replaced by green arrows after provincial standards were rewritten in 1999.[24] > > In Massachusetts, specifically in Cambridge and Somerville, the main street will have a flashing green signal, while cross streets have a signal that have a red on top, yellow in the middle and flashing red in the bottom position. When a pedestrian activates the signal, the cross street changes from flashing red in the lowest position to yellow to red (topmost position). > > In several European countries and Mexico, a flashing green light is used in crosswalks to indicate that signal is going to change from green to red soon. Therefore, flashing green has roughly the same meaning to pedestrians as ordinary yellow signal has for motorists. Slow-moving pedestrians are warned about oncoming signal change and have opportunity to wait for next signal cycle. Motorists are more likely to notice flashing signal. Drivers of vehicles about to cross pedestrian crossings should be more aware of incoming pedestrians. > > Current users of flashing green signal are Austria, Belgium, Estonia, Finland, Great Britain, Hungary, Netherlands, Norway, Mexico, Poland, Spain and Sweden. France, Portugal and Switzerland make limited use of flashing green. > > The new US 2009 Manual on Uniform Traffic Control Devices specifically prohibits flashing any green signal indication.[25] > **[Variations in traffic light operation](https://en.wikipedia.org/wiki/Traffic-light_signalling_and_operation)** > > In traffic engineering, there are regional and national variations in traffic light operation. This may be in the standard traffic light sequence (such as the inclusion of a red-amber phase) or by the use of special signals (such as flashing amber or public transport signals). > In the United States and Canada, a flashing red light is the equivalent of a stop sign. > In New Zealand, Hong Kong and the United Kingdom, paired red/red traffic lights are often installed outside fire and ambulance sta...