Span Wire Vs Mast Arm

[DrSmith]

I'll use a few examples here:
https://goo.gl/maps/Fs19Pnv8FR28gQ3u9

As a side note, when I was young my parents and grandparents said that the traffic signal at that intersection in Woodbury was manually operated by a cop. There was a small telephone booth like spot where the cop would operate the signal.

[roadfro]

Edit: If someone can show that TCO of a mast arm is lower, despite the higher initial cost, I might be more amenable to them. I'm not an engineer, so maybe I'm missing something.

I don't have the data for this on a whole, but here is a Florida example: https://news.ufl.edu/archive/1998/05/new-dampener-makes-traffic-light-poles-safer-longer-lasting.html. Miami-Dade went to universal mastarm installation after Hurricane Andrew because they only one mastarm in the county was damaged, while 2,700 span wire signals were damaged. Broward County lost 60% of their signals during a 2004 hurricane because they were predominately span wire. When cities and states are regularly having to replace failed signals, that increases costs.

I don't have definitive data on this, but I recall reading something several years ago about this. Installation cost for span wire is cheaper than mast arm. Regular operating costs should be identical. But ongoing maintenance costs are greater for span wire than mast arm. Span wire setups are more likely to need the signal heads realigned due to getting turned by weather, and the span wires themselves occasionally need to be re-tensioned...these costs are ongoing for the life of the signal and are almost completely absent with a mast arm or similar setup.

[democratic nole]

Edit: If someone can show that TCO of a mast arm is lower, despite the higher initial cost, I might be more amenable to them. I'm not an engineer, so maybe I'm missing something.

I don't have the data for this on a whole, but here is a Florida example: https://news.ufl.edu/archive/1998/05/new-dampener-makes-traffic-light-poles-safer-longer-lasting.html. Miami-Dade went to universal mastarm installation after Hurricane Andrew because they only one mastarm in the county was damaged, while 2,700 span wire signals were damaged. Broward County lost 60% of their signals during a 2004 hurricane because they were predominately span wire. When cities and states are regularly having to replace failed signals, that increases costs.

I don't have definitive data on this, but I recall reading something several years ago about this. Installation cost for span wire is cheaper than mast arm. Regular operating costs should be identical. But ongoing maintenance costs are greater for span wire than mast arm. Span wire setups are more likely to need the signal heads realigned due to getting turned by weather, and the span wires themselves occasionally need to be re-tensioned...these costs are ongoing for the life of the signal and are almost completely absent with a mast arm or similar setup.

I believe you are correct. I feel like someone posted that on this forum at some point, but I don't specifically remember.

[jakeroot]

^^^^^

Post mounted would work great as being non-obstrusive and is my recommendation as well for narrower streets.

The problem, of course, on wider streets is that if you are driving in the middle of a very wide street, you may not even see the signal.

Washington DC and San Francisco are two cities that come to mind with extensive use of post mounted and very little mast arm usage.  Chicago also has a lot of signals in the loop without mast arms, but almost every signal outside of the loop has them. 

More and more signals in DC are getting mast arms, but the arms are very short.  Due to aesthetic issues, certain streets in the core do not have mast arms at all, even very wide streets like Pennsylvania, Constitution, and Independence.

IMO, skipping mast arms works fine where streets are narrow like here:

https://www.google.com/maps/@38.8876148,-77.0006817,3a,75y,89.3h,90.48t/data=!3m6!1e1!3m4!1sjfOe5UzkX2To3PkK4ZVK4Q!2e0!7i16384!8i8192

but not fine for here:

https://www.google.com/maps/@38.8874352,-77.0218142,3a,75y,331.59h,93t/data=!3m7!1e1!3m5!1sTLPHCC7C22zV2bAE45_G2Q!2e0!6s%2F%2Fgeo3.ggpht.com%2Fcbk%3Fpanoid%3DTLPHCC7C22zV2bAE45_G2Q%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D106.30299%26pitch%3D0%26thumbfov%3D100!7i16384!8i8192

Agree with this post. DC would benefit from the installation of pedestal mounted signals on the near side of the intersection (because they do not permit mastarms for aesthetic reasons).

DC does actually use near side post-mounted signals, just not at every intersection.

For wider intersections, like Independence/7th, mast arms would definitely be wise but I think something like those used in Australia would be better, with a single mast arm with one signal head maybe extending over two lanes at most (CA has a lot of signals like this, although newer variations are longer). Multiple overhead signals and a mast arm that extends over three or four lanes becomes a very ugly sight in areas where there are additional concerns related to clear visibility of nearby landmarks or other aesthetic needs (with this also being a reason to use span wire, as wires are substantially thinner than mast arms and are easier to "look past" than a mast arm).

[democratic nole]

^^^^^

Post mounted would work great as being non-obstrusive and is my recommendation as well for narrower streets.

The problem, of course, on wider streets is that if you are driving in the middle of a very wide street, you may not even see the signal.

Washington DC and San Francisco are two cities that come to mind with extensive use of post mounted and very little mast arm usage.  Chicago also has a lot of signals in the loop without mast arms, but almost every signal outside of the loop has them. 

More and more signals in DC are getting mast arms, but the arms are very short.  Due to aesthetic issues, certain streets in the core do not have mast arms at all, even very wide streets like Pennsylvania, Constitution, and Independence.

IMO, skipping mast arms works fine where streets are narrow like here:

https://www.google.com/maps/@38.8876148,-77.0006817,3a,75y,89.3h,90.48t/data=!3m6!1e1!3m4!1sjfOe5UzkX2To3PkK4ZVK4Q!2e0!7i16384!8i8192

but not fine for here:

https://www.google.com/maps/@38.8874352,-77.0218142,3a,75y,331.59h,93t/data=!3m7!1e1!3m5!1sTLPHCC7C22zV2bAE45_G2Q!2e0!6s%2F%2Fgeo3.ggpht.com%2Fcbk%3Fpanoid%3DTLPHCC7C22zV2bAE45_G2Q%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D106.30299%26pitch%3D0%26thumbfov%3D100!7i16384!8i8192

Agree with this post. DC would benefit from the installation of pedestal mounted signals on the near side of the intersection (because they do not permit mastarms for aesthetic reasons).

DC does actually use near side post-mounted signals, just not at every intersection.

For wider intersections, like Independence/7th, mast arms would definitely be wise but I think something like those used in Australia would be better, with a single mast arm with one signal head maybe extending over two lanes at most (CA has a lot of signals like this, although newer variations are longer). Multiple overhead signals and a mast arm that extends over three or four lanes becomes a very ugly sight in areas where there are additional concerns related to clear visibility of nearby landmarks or other aesthetic needs (with this also being a reason to use span wire, as wires are substantially thinner than mast arms and are easier to "look past" than a mast arm).

I don't agree that span wires are better for aesthetics. Neither does the District of Columbia: https://www.washingtonpost.com/archive/local/1988/06/10/in-california-easy-to-see-traffic-signals-and-street-signs-are-no-dream/5578117f-5420-4d07-a71b-28afd27c39dc/
"Span-wire traffic signals are banned in the District of Columbia because the people in charge of aesthetics won't allow them to befoul the capital. Full-size span arm signals are out because they'd seem overpowering on the mostly narrow city streets, according to George Schoene, the District's traffic chief."

I think the smaller California mastarms would be fine, like this:https://goo.gl/maps/1sP37EENhKgSGnsG6

[mrsman]

^^^^^

Post mounted would work great as being non-obstrusive and is my recommendation as well for narrower streets.

The problem, of course, on wider streets is that if you are driving in the middle of a very wide street, you may not even see the signal.

Washington DC and San Francisco are two cities that come to mind with extensive use of post mounted and very little mast arm usage.  Chicago also has a lot of signals in the loop without mast arms, but almost every signal outside of the loop has them. 

More and more signals in DC are getting mast arms, but the arms are very short.  Due to aesthetic issues, certain streets in the core do not have mast arms at all, even very wide streets like Pennsylvania, Constitution, and Independence.

IMO, skipping mast arms works fine where streets are narrow like here:

https://www.google.com/maps/@38.8876148,-77.0006817,3a,75y,89.3h,90.48t/data=!3m6!1e1!3m4!1sjfOe5UzkX2To3PkK4ZVK4Q!2e0!7i16384!8i8192

but not fine for here:

https://www.google.com/maps/@38.8874352,-77.0218142,3a,75y,331.59h,93t/data=!3m7!1e1!3m5!1sTLPHCC7C22zV2bAE45_G2Q!2e0!6s%2F%2Fgeo3.ggpht.com%2Fcbk%3Fpanoid%3DTLPHCC7C22zV2bAE45_G2Q%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D106.30299%26pitch%3D0%26thumbfov%3D100!7i16384!8i8192

Agree with this post. DC would benefit from the installation of pedestal mounted signals on the near side of the intersection (because they do not permit mastarms for aesthetic reasons).

DC does actually use near side post-mounted signals, just not at every intersection.

For wider intersections, like Independence/7th, mast arms would definitely be wise but I think something like those used in Australia would be better, with a single mast arm with one signal head maybe extending over two lanes at most (CA has a lot of signals like this, although newer variations are longer). Multiple overhead signals and a mast arm that extends over three or four lanes becomes a very ugly sight in areas where there are additional concerns related to clear visibility of nearby landmarks or other aesthetic needs (with this also being a reason to use span wire, as wires are substantially thinner than mast arms and are easier to "look past" than a mast arm).

I don't agree that span wires are better for aesthetics. Neither does the District of Columbia: https://www.washingtonpost.com/archive/local/1988/06/10/in-california-easy-to-see-traffic-signals-and-street-signs-are-no-dream/5578117f-5420-4d07-a71b-28afd27c39dc/
"Span-wire traffic signals are banned in the District of Columbia because the people in charge of aesthetics won't allow them to befoul the capital. Full-size span arm signals are out because they'd seem overpowering on the mostly narrow city streets, according to George Schoene, the District's traffic chief."

I think the smaller California mastarms would be fine, like this:https://goo.gl/maps/1sP37EENhKgSGnsG6

Near sided post mounted signals can be used to address the width of the cross street, and like jakeroot mentions do exist in many places in DC without running afoul of the aesthetic rules.

The problem is the width of the street you may be on, and those can only be addressed with signal faces in the middle of the street.  The common ways of handling that are mast arms, span wire, or post mounted signals on a cement island.  Span wire, to my knowledge, does not exist in DC at all except temporary installations.  Pennsylvania Avenue does post mount signals in the median.  But Constitution and Independence through much of Downtown are 8 lanes wide without an island and generally without mast arms.  With the benefit of experience, I can tell you that if you are driving in the left lane on those streets, it can be quite easy to miss one of the sidemounted signals because the streets are so wide.

[jeffandnicole]

I'll use a few examples here:
https://goo.gl/maps/Fs19Pnv8FR28gQ3u9

As a side note, when I was young my parents and grandparents said that the traffic signal at that intersection in Woodbury was manually operated by a cop. There was a small telephone booth like spot where the cop would operate the signal.

Great memory!

Yep, when *I* remember it, the small shack was located on this corner, about where the control boxes are located: https://goo.gl/maps/p8GCe1ZMMp91aUxp7 .  I want to say the traffic signal was upgraded in the 1980's, and as a result the new signal wouldn't permit an override function the old signal had (I find that a little hard to believe as I've seen even more modern signals in the state operated by police, but I remember that being reported at the time).

I tried looking on the web for that shack and couldn't find a picture, but I did come across this picture which shows an even earlier version of the traffic lights at the intersection and a shack house which would've been across the street of that above image (https://www.flickr.com/photos/nat507/4781232743/) , which would be this corner: https://goo.gl/maps/zkfFVV5aGFZ2VV496.  As you can see, the old courthouse remains, and even has the same monument out front.

[jakeroot]

For wider intersections, like Independence/7th, mast arms would definitely be wise but I think something like those used in Australia would be better, with a single mast arm with one signal head maybe extending over two lanes at most (CA has a lot of signals like this, although newer variations are longer). Multiple overhead signals and a mast arm that extends over three or four lanes becomes a very ugly sight in areas where there are additional concerns related to clear visibility of nearby landmarks or other aesthetic needs (with this also being a reason to use span wire, as wires are substantially thinner than mast arms and are easier to "look past" than a mast arm).

I don't agree that span wires are better for aesthetics. Neither does the District of Columbia: https://www.washingtonpost.com/archive/local/1988/06/10/in-california-easy-to-see-traffic-signals-and-street-signs-are-no-dream/5578117f-5420-4d07-a71b-28afd27c39dc/
"Span-wire traffic signals are banned in the District of Columbia because the people in charge of aesthetics won't allow them to befoul the capital. Full-size span arm signals are out because they'd seem overpowering on the mostly narrow city streets, according to George Schoene, the District's traffic chief."

I think the smaller California mastarms would be fine, like this:https://goo.gl/maps/1sP37EENhKgSGnsG6

"Neither does the District of Columbia" is a stretch when you cite an article from 1988. More accurately, I think it's best stated that DC "has traditionally not used span wire as they are not in keeping with the aesthetics of the district". Comparetively, span wire is not as much of an aesthetic concern in Seattle given the sheer number of existing non-signal wires overhead along many city streets. DC does not have this problem so span wire signals would look very odd.

You seem to be operating under the assumption that span wire is always worse. I would say that, in 90% of circumstances, span wire is worse. But there are situations where span wire can be appropriate. The catch is that it's not just span wire vs mast arm vs post-mounted...it's span wire versus an indeterminate number of overhead signals, mast arm thickness, and mast arm length ...versus post-mounted. There is a wide range of mast arm designs, and they are rarely created equal: DC's short mast arms are far better than this hulking behemoth in Seattle, for example, despite both being mast arm signals. Many of LA's mast arms with a single overhead signal (as you already linked to above) are indeed a great setup that really should be used far more often than it is. DC could stand to use a variation of that.

[mrsman]

Slightly off-topic, but if you click on the link in jakeroot's post, you see a very interesting building.  I read up a little on it and its called Rainier Tower.  It is 40 stories tall, but 29 stories are offices that sit on an 11 story concrete pedestal, shaped like an inverted pyramid.  Its so odd to see a building like that where 11 stories are essentially unused for retail, offices, or parking.

[democratic nole]

For wider intersections, like Independence/7th, mast arms would definitely be wise but I think something like those used in Australia would be better, with a single mast arm with one signal head maybe extending over two lanes at most (CA has a lot of signals like this, although newer variations are longer). Multiple overhead signals and a mast arm that extends over three or four lanes becomes a very ugly sight in areas where there are additional concerns related to clear visibility of nearby landmarks or other aesthetic needs (with this also being a reason to use span wire, as wires are substantially thinner than mast arms and are easier to "look past" than a mast arm).

I don't agree that span wires are better for aesthetics. Neither does the District of Columbia: https://www.washingtonpost.com/archive/local/1988/06/10/in-california-easy-to-see-traffic-signals-and-street-signs-are-no-dream/5578117f-5420-4d07-a71b-28afd27c39dc/
"Span-wire traffic signals are banned in the District of Columbia because the people in charge of aesthetics won't allow them to befoul the capital. Full-size span arm signals are out because they'd seem overpowering on the mostly narrow city streets, according to George Schoene, the District's traffic chief."

I think the smaller California mastarms would be fine, like this:https://goo.gl/maps/1sP37EENhKgSGnsG6

"Neither does the District of Columbia" is a stretch when you cite an article from 1988. More accurately, I think it's best stated that DC "has traditionally not used span wire as they are not in keeping with the aesthetics of the district". Comparetively, span wire is not as much of an aesthetic concern in Seattle given the sheer number of existing non-signal wires overhead along many city streets. DC does not have this problem so span wire signals would look very odd.

You seem to be operating under the assumption that span wire is always worse. I would say that, in 90% of circumstances, span wire is worse. But there are situations where span wire can be appropriate. The catch is that it's not just span wire vs mast arm vs post-mounted...it's span wire versus an indeterminate number of overhead signals, mast arm thickness, and mast arm length ...versus post-mounted. There is a wide range of mast arm designs, and they are rarely created equal: DC's short mast arms are far better than this hulking behemoth in Seattle, for example, despite both being mast arm signals. Many of LA's mast arms with a single overhead signal (as you already linked to above) are indeed a great setup that really should be used far more often than it is. DC could stand to use a variation of that.

I do operate under the assumption that span wire is always worse. The upfront install cost is what drives DOT's to use span wire more than almost anything else. Even at large intersections, I would rather have multiple mastarms than use of span wire. However, I also have the belief that cities and municipalities should not be installing 8-10 lane uncontrolled access roads with signals. If the road needs to be that large, build a freeway.

If you think that Seattle signal is a behemoth, you would really hate some of these Florida mastarms, as I do. Some links:
https://goo.gl/maps/6RxerGSw9psJabwy9
https://goo.gl/maps/io3gQ2b1Y3nRRhgt7
https://goo.gl/maps/u8KTseeY47mjWC8f9

[jakeroot]

For wider intersections, like Independence/7th, mast arms would definitely be wise but I think something like those used in Australia would be better, with a single mast arm with one signal head maybe extending over two lanes at most (CA has a lot of signals like this, although newer variations are longer). Multiple overhead signals and a mast arm that extends over three or four lanes becomes a very ugly sight in areas where there are additional concerns related to clear visibility of nearby landmarks or other aesthetic needs (with this also being a reason to use span wire, as wires are substantially thinner than mast arms and are easier to "look past" than a mast arm).

I don't agree that span wires are better for aesthetics. Neither does the District of Columbia: https://www.washingtonpost.com/archive/local/1988/06/10/in-california-easy-to-see-traffic-signals-and-street-signs-are-no-dream/5578117f-5420-4d07-a71b-28afd27c39dc/
"Span-wire traffic signals are banned in the District of Columbia because the people in charge of aesthetics won't allow them to befoul the capital. Full-size span arm signals are out because they'd seem overpowering on the mostly narrow city streets, according to George Schoene, the District's traffic chief."

I think the smaller California mastarms would be fine, like this:https://goo.gl/maps/1sP37EENhKgSGnsG6

"Neither does the District of Columbia" is a stretch when you cite an article from 1988. More accurately, I think it's best stated that DC "has traditionally not used span wire as they are not in keeping with the aesthetics of the district". Comparetively, span wire is not as much of an aesthetic concern in Seattle given the sheer number of existing non-signal wires overhead along many city streets. DC does not have this problem so span wire signals would look very odd.

You seem to be operating under the assumption that span wire is always worse. I would say that, in 90% of circumstances, span wire is worse. But there are situations where span wire can be appropriate. The catch is that it's not just span wire vs mast arm vs post-mounted...it's span wire versus an indeterminate number of overhead signals, mast arm thickness, and mast arm length ...versus post-mounted. There is a wide range of mast arm designs, and they are rarely created equal: DC's short mast arms are far better than this hulking behemoth in Seattle, for example, despite both being mast arm signals. Many of LA's mast arms with a single overhead signal (as you already linked to above) are indeed a great setup that really should be used far more often than it is. DC could stand to use a variation of that.

I do operate under the assumption that span wire is always worse. The upfront install cost is what drives DOT's to use span wire more than almost anything else. Even at large intersections, I would rather have multiple mastarms than use of span wire. However, I also have the belief that cities and municipalities should not be installing 8-10 lane uncontrolled access roads with signals. If the road needs to be that large, build a freeway.

If you think that Seattle signal is a behemoth, you would really hate some of these Florida mastarms, as I do. Some links:
https://goo.gl/maps/6RxerGSw9psJabwy9
https://goo.gl/maps/io3gQ2b1Y3nRRhgt7
https://goo.gl/maps/u8KTseeY47mjWC8f9

It seems a bit unfair to assume that it's always worse. Even that ancient article you cited indicates that most agencies that use mast arms chose to do so purely out of aesthetic preference. For those areas that use them to better weather storms, Seattle does not meet this criteria: mild weather, no hurricanes, wind is only an occasional issue, etc. At this point, the possibility of choosing span wire for aesthetics becomes possible. For years, Seattle's preference was simply to use one or the other, depending on the circumstances (Seattle has used mast arms for decades), but those circumstances seemed to dictate that the downtown core would use span wire or post mounted signals, and the suburbs would largely use mast arm or span wire depending on the individual circumstances.

The more I think about it, the more I realize that span wire was likely most common early on because larger mast arms weren't available (these are typical old Seattle mast arms). In the downtown core, where you'd have four or five through lanes along a one-way street, having a small mast arm on one side wasn't considered "good enough" so they used span wire to centre the signals. This is probably why, for decades, only 4th Ave downtown ever used span wire: most of 1st, 2nd, 3rd, 5th, 6th, and 7th used post mounted only signals because 4th was the widest (2nd was close in width, but still used post-mounted signals). Span wire briefly became common along some streets (chiefly 2nd in the Belltown area and parts of 6th and 7th), but mast arms have since become far more common: 2nd, 5th, 6th, 7th...these streets all have multiple examples along them, almost all new within the last ten years.

tl;dr...Seattle likely had reasons to use span wire in the past, be it for aesthetic or technical reasons, but new span wire is not installed downtown (simply maintained, such as long 4th Ave), and mast arms or post mounted signals are now the norm only (new span wire installations seem to have ended about 8 or 10 years ago). Don't worry about maintaining a fight here, since you already won!

Also, yes, those signals in Florida are awful. Although it should be noted that those are all suburban environments where massive, hulking mast arms don't necessarily look out of place. They do look stupid there (way overbuilt IMO), but they'd look hilariously stupid in a downtown core.

[jakeroot]

Slightly off-topic, but if you click on the link in jakeroot's post, you see a very interesting building.  I read up a little on it and its called Rainier Tower.  It is 40 stories tall, but 29 stories are offices that sit on an 11 story concrete pedestal, shaped like an inverted pyramid.  Its so odd to see a building like that where 11 stories are essentially unused for retail, offices, or parking.

Designed by none other than Minoru Yamasaki, perhaps most noted for the original World Trade Center towers. It is a rather odd building. According to this article from the University of Washington:

"[t]he unusual tapered base was selected for multiple reasons. First, its form proved highly effective in resisting huge seismic jolts that could affect Seattle. Second, Yamasaki wanted to preserve the "green" character of Downtown Seattle, and therefore wanted to minimize the building's footprint on the site. Third, he wanted to devote much of the ground space to a retail shopping plaza. Fourth, clearly, Yamasaki also was enamored of the base's soaring, curved form."

With the adjacent Rainier Square Tower now complete, it's fair to say that this block has more curving buildings than any other part of Seattle!

[democratic nole]

tl;dr...Seattle likely had reasons to use span wire in the past, be it for aesthetic or technical reasons, but new span wire is not installed downtown (simply maintained, such as long 4th Ave), and mast arms or post mounted signals are now the norm only (new span wire installations seem to have ended about 8 or 10 years ago). Don't worry about maintaining a fight here, since you already won!

Also, yes, those signals in Florida are awful. Although it should be noted that those are all suburban environments where massive, hulking mast arms don't necessarily look out of place. They do look stupid there (way overbuilt IMO), but they'd look hilariously stupid in a downtown core.

LOL. I think the reason I always get fired up about the availability of mastarms argument is that California never used span wire and managed to use guy-wire mastarms going back probably to the 50's at larger intersections.

BTW, I can give you the bulky mastarms downtown here too: https://goo.gl/maps/QXENvi9Ei6RzC2298 https://goo.gl/maps/5VyBoQEsBU5jxWbW6 https://goo.gl/maps/7K4Q58Qiw9QBiPXm6

[Scott5114]

I'm guessing there's something wonky about NJ's signal placement that makes that an ongoing concern.

They're just placed way too close to the roadway.  Trucks making tight right turns often can snag it, or a crash within the intersection can send a car into it. 

Here, the masts are typically placed on the far side of the sidewalk from the intersection. If, for some reason, the mast has to be placed closer, it is protected by a much higher curb than seems to be the case in NJ. (You can see this at one of the other corners of this intersection.)