What style of traffic light is this?

[CapeCodder]

https://www.google.com/maps/@41.657634,-70.269048,3a,15y,272.16h,93.14t/data=!3m6!1e1!3m4!1sBr_SJgdu3K8AeuwRSM15AQ!2e0!7i16384!8i8192

It's the only one of its type on Cape Cod (that I'm aware of), but yet St. Louis has hundreds. When did this type first appear?

It's one of those lights where if you turn away from it, the light disappears, like a prism.

[cjw2001]

https://highwaydivides.com/wiki/index.php?title=3M#M-131_Programmable_Visibility_Traffic_Signal

[STLmapboy]

St. Louis MO? Not a ton nowadays (Chicago has more). Given the diversity of MA signals I'm surprised how few there are in the state.

[mrsman]

 

St. Louis MO? Not a ton nowadays (Chicago has more). Given the diversity of MA signals I'm surprised how few there are in the state.

3M signals are ideal at acute angle intersections, so that only the proper direction can see the signal.  Given how many 6 point intersections there are in Chicago with streets like Ogden and Milwaukee running diagonally through, it makes sense to see a bunch of those there.

[jmacswimmer]

I've also seen 3M's used where there's 2 signals on the same road in close proximity to each other, here's an example.

[Amtrakprod]

St. Louis MO? Not a ton nowadays (Chicago has more). Given the diversity of MA signals I'm surprised how few there are in the state.

We actually have a ton. He's just talking about in Cape Cod.


iPhone

[mrsman]

I've also seen 3M's used where there's 2 signals on the same road in close proximity to each other, here's an example.

Another good use of the 3M.

I don't believe they are in use in NYC.  There was some intersection that I was on in Brooklyn, I forget where, where there are two separate signals in very close proximity.  I saw the further light go green and almost proceeded, but fortunately my wife alerted me to the red light in front of me.  A 3M on the further signal would have been a good safety measure there.

Also, 3Ms used to be used in CA (and other western states) as the red signal on a left turn signal.  This way the red signal would not confuse drivers in the adjacent lanes who may have a green to go straight but a red for turning left.  Nowadays, these have been replaced with red arrow signals, for the better IMO.

There are still some states with the red orb-yellow arrow-green arrow signal (PA, VA) that do not use the 3M, but put in place a "left turn signal sign"

[roadfro]

Also, 3Ms used to be used in CA (and other western states) as the red signal on a left turn signal.  This way the red signal would not confuse drivers in the adjacent lanes who may have a green to go straight but a red for turning left.  Nowadays, these have been replaced with red arrow signals, for the better IMO.

There's still a couple of these on older signals in Sparks, NV. These left turn 3M signals use circular red/circular yellow/green arrow indications, but are always accompanied by supplemental far left post-mounted signal head that is a more modern all-arrow display. Example