I have been figuring out what to do about signal bridges. When I was laying track, I followed the John Armstrong track centers measurement guidelines for straights and curves. It never occurred to me that I should also be anticipating spacing for trackside devices and that brings me here.
I just bought an MTH 30-11030 "0 Scale Pennsy Signal Bridge". It seems quite a bit larger (I guess "wider" might be the issue) than my other signal bridges accumulated over the years. The pix show the story.
The last bridge pictured is the MTH. The first three in order are the Plasticville, Lionel and Z-stuff semaphore bridge. As you can see, the first 3 bridges are just about the same width. But the MTH is a different animal. I can use it elsewhere on my layout. But it sure doesn't fit in my little 4-track yard.
If you are wanting one or more signal bridges in your yard, maybe it would be best to do some measurements and test-fitting to make sure your will fit. Some do, some don't.