Growing up in New Jersey from 1965 to 1990 I have seen many traffic light replacements throughout those years. I have seen them all from total signal replacements to just one pole to even just replace the mast arm only, but leave the same pole. Believe me I have seen a lot of them.
Anyway, when NJ was going from double guy to truss style mast arms I would notice that instead of building a completely new signal pole and mast arm like most places around where I live does, they would remove the old pole and erect the new pole on the same exact mooring.
I actually think that this is great as no need for new construction as New Jersey always used the same pole base for traffic signals as many have always used for freeway lamp posts with the box at the bottom. So easily the parts are interchangeable so why go through more money and trouble on the installations? However, places like Florida would, even with just one pole being replaced, just build a new mooring and erect the new pole adjacent to the one being replaced. Then have to not only remove the existing assembly later, but have to jackhammer out the old foundations.
Now I have not been in all the areas in the US to notice how everyone else does it. All I know is Florida verses New Jersey as these are the only states that I have lived in. I am guessing that Florida's method is most common. However, I was just wondering why can't all signal pole replacements use the same base as the previous ones and furthermore why can't if the situation calls for the mast arm only to be replaced, why not do just that.
In Cranford, NJ when the Township decided to replace the mast arms from double guy to truss style back in the 80s, they left the original poles standing and just replaced the arms. So they actually did one better to save money on their own taxpayers. Why go through the added expenditures?
Every signal replacement project I've seen in Florida was usually replacing an old wire-span installation with mast-arms. Florida usually uses concrete poles for wire-span installations. I'm not an engineer but I would think whatever they are using to anchor the concrete poles into the ground isn't compatible with the moorings needed for a much heavier mast arm.
I don't recall ever seeing a mast arm replaced with another mast arm.
I've seen a few mast arms replace other mast arms, including one where they installed a new mast-arm and mounted the old signals on it.
California almost never uses wire-spans except for temporary signals. For longer cantilevers, they have to use a larger diameter mast and a different brace-joint.
Quote from: KEK Inc. on April 20, 2015, 03:40:22 PM
California almost never uses wire-spans except for temporary signals. For longer cantilevers, they have to use a larger diameter mast and a different brace-joint.
Nevada is similar. Some older poles are slightly thinner or do not conform to current design standards for anchorage. So this means a new base foundation or new mast pole is needed.
Also, many times if the pole is being replaced, it is due to a widening project. This will require either a pole moved to a new location, or new wider mast pole which would require a new base anyway.
Nevada has developed some standard designs for signal poles and mast arms. This does allow for some limited applications of directly swapping a mast arm with a new one, as long as the existing pole is sufficient structurally to carry the weight of the new mast arm and signal head load.
It is true for a lot of New York City intersections. Most traffic signals of today are located on the same foundations as their predecessors (red and green lights) once were years ago.
Quote from: KEK Inc. on April 20, 2015, 03:40:22 PM
California almost never uses wire-spans except for temporary signals. For longer cantilevers, they have to use a larger diameter mast and a different brace-joint.
Illinois is similar, but some of the "temporary" signals can be a bit permanent as they'll be up for many years before the road is widened, the intersection is improved, or the intersection gets permanent signals.
Quote from: M3019C LPS20 on April 23, 2015, 01:52:27 AM
It is true for a lot of New York City intersections. Most traffic signals of today are located on the same foundations as their predecessors (red and green lights) once were years ago.
NYC also uses one type of pole which makes them very interchangable. The short pole for the 8 foot side mounted have the same base as the overhead ones, so they can interchange so easily.
I also noticed that New York many times uses a pole that is not round and hollow either. Some are with two "u" s together especially in Manhattan sort of like the posts on some signs. Then many Manhattan signals use the corner street lamp poles to attach the mast arms to rather than add another pole just for the signal assembly. The mast arms on the street lamps do not even put a strain on the street lamp assembly either probably because their mast arms are so thin.
(https://farm8.staticflickr.com/7673/17094036958_c6d14eaa6b.jpg) Speaking of interchanging span wire to mast arms here is one that suggests it can be done. A temporary set up on one of Texas roads during construction uses a metal span wire pole to support a mast arm.
Quote from: roadman65 on April 29, 2015, 08:29:09 AM
(https://farm8.staticflickr.com/7673/17094036958_c6d14eaa6b.jpg) Speaking of interchanging span wire to mast arms here is one that suggests it can be done. A temporary set up on one of Texas roads during construction uses a metal span wire pole to support a mast arm.
That traffic signal had been there before construction (on the Grand Parkway, BTW) had started.
(https://farm7.staticflickr.com/6220/6316501017_b5047cda3a.jpg) (https://flic.kr/p/aCaHFX)Entrance to Spring Trails (https://flic.kr/p/aCaHFX) by FreewayDan (https://www.flickr.com/people/22306412@N07/), on Flickr