It was a lot of a mystery for me to understand why the US and Canada, have lot of their traffic lights horizontally mounted, while in the rest part of the world (Including Israel), they are always vertically mounted.
When I've searched in Google if in the US and Canada, there is a different meaning for the flashing yellow light in traffic lights than in the rest part of the world (In Israel, flashing yellow light meaning that the traffic light system is malfunctioning or not working, and that you need to drive according to the traffic signs), I encountered the following page, which discusses about this question, why North America and Japan, are the world's only countries with horizontally mounted traffic lights: https://www.driverknowledgetests.com/resources/why-are-traffic-lights-in-the-usa-and-some-other-countries-horizontal

Based on my visits there, I don't think MOST are horizontal, but FEW indeed were. And it is true, here (Czech Rep) the only legal position is vertical with the red on the top.

I can't speak for the USA, but in Canada, most traffic lights outside Québec are vertical. Most traffic lights in Québec are horizontal if mounted overhead and vertical on poles at the side of the road. I could never see a reason for this other than tradition. There are exceptions, but they are rather rare.

Of note here, there is a certain percentage of the Québec population who identify as separatists, who would like Québec to become an independent country. While not the case at the moment (Québec is a province of Canada), they do have differences from the rest of Canada. It might explain part of the traffic light difference.

Also of note, there are French-speaking populations outside of Québec. I am one of those, I am not from Québec (nor France) although my first language is French.

Just about of the traffic lights i've seen are vertical, i don't think i've ever seen any horizontal traffic lights out here.

Never seen any horizontal traffic lights here, or when I've been to the US, come to that. Although I've only ever driven in California, all the lights I've seen there have been the usual vertical arrangement.

All the traffic lights in battle creek are verticle. I've seen horizontal traffic lights but not nearly as often as I've seen verticle ones..

All the traffic lights in battle creek are verticle. I've seen horizontal traffic lights but not nearly as often as I've seen verticle ones..

I have only seen them in Wisconsin.

Our lights in America are mostly vertical, not horizontal.  Thankfully. 

Texas  Is one  few places in USA that do have Horizontal And Vertical Traffic signal. one of main
reasons  is there is lot oversize tall loads such as
oil production equpiment. Those can damage the vertical signal creating a hazard.  now they
have been mounting them vertical  with taller
traffic mask arms and use a bracket to alllow them
to mount them vertical in center of mask arms. giving
clearence they needed for oversize trucks.

Here in the UK we don't have the overhead traffic signals mounted on wires, there are some gantry mounted ones, but for the most part we know which signals apply to a specific lane.

Here in the UK we don't have the overhead traffic signals mounted on wires, there are some gantry mounted ones, but for the most part we know which signals apply to a specific lane.

WE do, but there are an awful lot of drivers that don't have a clue   Also, there's a no-right-turn sign just down the road from here, but hardly anyone ever takes any notice of it  

All the traffic-lights I've seen here have been vertical mounted...only place I've ever seen horizontal was in Canada.

15 years ago (fall 2003) I remember seeing quite a few horizontally mounted signals in Pocatello (Id) and about 10 years ago in Salt Lake City (both when I was visiting there). No idea, how it looks there now, if it remained or if it was reconstructed in the meantime...

I think your opinion on whether the US or Canada used more vertical or horizontal signals depends largely on the province or state you visit.

In Canada, Ontario is all vertical (Some test installs in the mid 20s were horizontal but we used vertical since the 30s), Quebec is mostly horizontal with the exception of Montreal which uses mostly vertical. It's been a while since I was there but I think Atlantic Canada was a mix of horizontal and vertical. In the US is around the same, some states are vertical only, some are horizontal only and some use both. NY is one of those states, they're mostly vertical but use horizontal signals on some underpasses due to clearance issues.

Japan is mostly horizontal (and surprisingly a good number of incandescent signals left) but I spotted some vertical ones during my visit.

I am currently visiting Moncton, New Brunswick and they have mostly horizontal ones here. I guess it has become more of a traditional thing depending on the region.