# Why aren't most traffic signals synchronized by now? **URL:** \ **Category:** Factual Questions\ **Created:** [March 12, 2007, 12:54am UTC](https://boards.straightdope.com/t/why-arent-most-traffic-signals-synchronized-by-now/395537 "2007-03-12T00:54:24Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![John\_DiFool](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_difool/32/19543_2.png) [@John\_DiFool](https://boards.straightdope.com/u/John_DiFool)\ **Post date:** [March 12, 2007, 12:54am UTC](https://boards.straightdope.com/t/why-arent-most-traffic-signals-synchronized-by-now/395537/1 "2007-03-12T00:54:24Z")
My town (Jacksonville) has miles and miles of roads. Only a scant few of them have synchronized traffic signals (mainly downtown); a typical light here may be green for virtually nobody, turns red, and then cars arrive and have to idle for a minute or two. Here it is the year 2007, so why hasn’t most of the town/state/country had such lights installed on their busiest thoroughfares? We’ve had the technology for a number of years now, so is it more of a fiscal issue than technological? ---
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [March 12, 2007, 12:59am UTC](https://boards.straightdope.com/t/why-arent-most-traffic-signals-synchronized-by-now/395537/2 "2007-03-12T00:59:26Z")
It could be a fiscal issue but how do you know that they aren’t synchronized? The common meaning to this is that cars can travel at a certain speed down one road and time it to all green lights. In reality, this is a hugely complex problem that can’t just look at one road. It has to look at all roads and how traffic is flowing throughout the city (which often follows fluid dynamics theory very closely). A steady stream of cars from one source may disrupt traffic in other places. Think of how often you count on a break in traffic on a major road to enter it yourself. I am not saying that any of this is the case here. I am just saying that “synchronizing lights” is a very simplistic solution to the overall issue. ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [March 12, 2007, 1:43am UTC](https://boards.straightdope.com/t/why-arent-most-traffic-signals-synchronized-by-now/395537/3 "2007-03-12T01:43:05Z")
Probably for the same reason your posts never line up properly. 😉 ---
**Author:** ![SmackFu](https://avatars.discourse-cdn.com/v4/letter/s/53a042/32.png) [@SmackFu](https://boards.straightdope.com/u/SmackFu)\ **Post date:** [March 12, 2007, 2:06am UTC](https://boards.straightdope.com/t/why-arent-most-traffic-signals-synchronized-by-now/395537/4 "2007-03-12T02:06:16Z")
[QUOTE=John DiFool] We’ve had the technology for a number of years now, so is it more of a fiscal issue than technological? [/QUOTE] Yes, clearly. Every light would probably need a new controller, which aren’t cheap. They would probably need a federal or state grant to fund it. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [March 12, 2007, 2:25am UTC](https://boards.straightdope.com/t/why-arent-most-traffic-signals-synchronized-by-now/395537/5 "2007-03-12T02:25:36Z")
Apparently the lack of synchronized traffic lights [is a problem in Jacksonville](http://jacksonville.bizjournals.com/jacksonville/stories/2005/05/30/story5.html). ---
**Author:** ![rock\_party](https://avatars.discourse-cdn.com/v4/letter/r/e19b73/32.png) [@rock\_party](https://boards.straightdope.com/u/rock_party)\ **Post date:** [March 12, 2007, 2:34am UTC](https://boards.straightdope.com/t/why-arent-most-traffic-signals-synchronized-by-now/395537/6 "2007-03-12T02:34:41Z")
What I don’t understand: why do they cycle lights so slow that the intersection is left “empty” and unused for long periods. Seems to me if the light would change after the last of the waiting “cluster” made it thur the intersection and let the opposing traffic go it would actually “pump” cars thru intersections. So often now you’re left at a red light staring at an empty intersection for far too long. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [March 12, 2007, 3:26am UTC](https://boards.straightdope.com/t/why-arent-most-traffic-signals-synchronized-by-now/395537/7 "2007-03-12T03:26:17Z")
[QUOTE=Exapno Mapcase] Apparently the lack of synchronized traffic lights [is a problem in Jacksonville](http://jacksonville.bizjournals.com/jacksonville/stories/2005/05/30/story5.html). [/QUOTE] [Jacksonville looks like an ugly town](http://maps.yahoo.com/maps_result?addr=&csz=Jacksonville&country=us&new=1) for traffic light ‘synchronization’. It has too many bridges and curvy roads. It seems even the grids of minor streets are broken up into misaligned pieces. ---
**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\ **Post date:** [March 12, 2007, 4:54am UTC](https://boards.straightdope.com/t/why-arent-most-traffic-signals-synchronized-by-now/395537/8 "2007-03-12T04:54:23Z")
Most cities in Los Angeles are synched so you cannot go more than 1 or 2 lights without hitting a red on purpose to control speed. I know someone will point out that properly synched lights will control speeding, but apparently many municipalities think they have a better plan. ---
**Author:** ![TheLoadedDog](https://avatars.discourse-cdn.com/v4/letter/t/35a633/32.png) [@TheLoadedDog](https://boards.straightdope.com/u/TheLoadedDog)\ **Post date:** [March 12, 2007, 12:46pm UTC](https://boards.straightdope.com/t/why-arent-most-traffic-signals-synchronized-by-now/395537/9 "2007-03-12T12:46:50Z")
Let’s say you have a simple grid pattern. East - west has secondary streets, and the main roads run north - south. You’re not going to be able to please everyone. I know a guy who designs the train timetables for a large city. People who have to change from one train to another will complain about the connections being crap. It’s definitely an extremely difficult job to get most of the people satisfied, as a tweak here will cause chaos there. Any form of traffic management on a complex system is a black art. ---
**Author:** ![Bridget\_Burke](https://avatars.discourse-cdn.com/v4/letter/b/7cd45c/32.png) [@Bridget\_Burke](https://boards.straightdope.com/u/Bridget_Burke)\ **Post date:** [March 12, 2007, 1:00pm UTC](https://boards.straightdope.com/t/why-arent-most-traffic-signals-synchronized-by-now/395537/10 "2007-03-12T13:00:46Z")
Most of Houston’s traffic lights are synchronized. > [@](#): > > MAYOR BILL WHITE ANNOUNCES COMPLETION OF RE-TIMING FOR 1,540 TRAFFIC SIGNALS > > Citywide Program On Time; Phase II to include almost 600 more signals > > January 6, 2005 – Mayor Bill White today announced the on-time, on-budget completion of a program to synchronize more than 1,500 traffic lights across the city to improve the flow of traffic. > > “This has been one of the most significant and effective things we’ve been able to do to improve Houstonians’ lives,” said Mayor White. “We’ve cut commuting times by as much as 20 percent in some corridors and that is valuable time we’re happy to see returned to our citizens. Houston is on the move.” [www.houstontx.gov/mayor/press/20050106.html](http://www.houstontx.gov/mayor/press/20050106.html) I use mass transit (bus & light rail) for my commute, so I can’t judge how well this works in the heaviest traffic. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [March 12, 2007, 3:33pm UTC](https://boards.straightdope.com/t/why-arent-most-traffic-signals-synchronized-by-now/395537/11 "2007-03-12T15:33:03Z")
It’s often not a simple matter, and sometimes impossible to synchronize everything. Take an East-West artery. If the lights are synchronized for eastbound traffic, rarely will they then automatically be synchronized for westbound traffic. Add complications like necessary minimum and maximum durations for red and green lights, and that major cross streets may occur at odd intervals because of how the area developed, and the prospect of synchronizing gets swallowed in a complex maze of conflicting requirements. Not to say that things can’t be improved or optimized, but the notion that most of it can be synchronized is sometimes a pipe dream. ---
**Author:** ![Hampshire](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hampshire/32/4887_2.png) [@Hampshire](https://boards.straightdope.com/u/Hampshire)\ **Post date:** [March 12, 2007, 4:15pm UTC](https://boards.straightdope.com/t/why-arent-most-traffic-signals-synchronized-by-now/395537/12 "2007-03-12T16:15:31Z")
Our local news ran a story reguarding this last year. They showed a main drag somewhere in Phoenix and rode with the mayor as they set their speed to the speed limit and cruised from one end of town to the other non-stop. He was pretty proud of their synched lights. Then they showed an artery in Minneapolis (Lake Street I believe) and how it was absolutely f’d up. They said it could run as smoothly as the Phoenix street and it did at one time but after various power outages over the years it just gets screwed up. They said the big problem was money in the budget to reset them. Apparently they need to be set manually at the actual light itself. This somehow required a crew of two and a cherry picker. I would think some upgraded technology with lights synched remotely from a mainframe would be something cities would put in their budgets but apparently not. I think they rather dump the money into snow removal and pothole filling. ---
**Author:** ![Tastes\_of\_Chocolate](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tastes_of_chocolate/32/3232_2.png) [@Tastes\_of\_Chocolate](https://boards.straightdope.com/u/Tastes_of_Chocolate)\ **Post date:** [March 12, 2007, 5:04pm UTC](https://boards.straightdope.com/t/why-arent-most-traffic-signals-synchronized-by-now/395537/13 "2007-03-12T17:04:03Z")
[QUOTE=Hampshire] Our local news ran a story reguarding this last year. They showed a main drag somewhere in Phoenix and rode with the mayor as they set their speed to the speed limit and cruised from one end of town to the other non-stop. He was pretty proud of their synched light. Then they showed an artery in Minneapolis (Lake Street I believe) and how it was absolutely f’d up. [/QUOTE] That’s all fine and dandy for people travelling on that one road, with the mayor picking a time when traffic flows smoothly. I don’t think it would be physically possible to get Lake Street in Minneapolis to flow that way. Between pedestrians, people pulling into and out of parking spots, and buses stopping for passengers, even if you synched the lights for idea conditions, the real life driving would never support that.