Earlier quoted context omitted.
OpenCV on a Raspberry does not sound like something that is reliable and easy to deploy. It‘s a long way to go from something that you hack together in the living room to something you can deploy on hundreds of traffic lights, that works in every weather, that can easily be configured for different use cases, and that can be serviced by the technicians.
It can be: https://resin.io A Raspberry Pi is a surprisingly useful and cost effective device when it comes to IOT. Most industrially hardened devices of similar capacity cost a bit north of an order of magnitude more. There are really only a couple of things that would need to be addressed, a good weather-tight case that allowed for heat dissipation, decent storage (most microSD has a short lifespan), and a good 5v…
Yes, you can make the software deployment go easier, and resin looks like an interesting project from that front. But that really is only a small part of the problen, and those hardware problems you described aren't trivial. The testing you described to convincingly show that your device can handle the environmental requirements isn't trivial. (And by environmental, I dont just mean weather, but also things like available power quality, vibration, etc.)
These industrial devices aren't expensive just because the suppliers aren't aware of RasPi, or are looking to gouge you. Its because they put in a lot of work to qualify these devices for their intended conditions. The RasPi, hacked up solution might actually be the WAY more expensive option over it's lifetime, if I have to roll maintenance crews every couple of months to replace SD cards or fix a flaky connector. And god forbid our code hangs in a way that makes all of the lights at an intersection green. "Oh you have a way to prevent that? Prove it." Designed to fail works fine for microservices where I can spin up a new instance rapidly, but it isn't the best match for industrial or infrastructure in most cases.
Apologies if I'm coming across overly snarky here. I genuinely love the RaspPi, and its got a great niche for prototyping, hacking up one-off projects, or even as the base for many types of connected projects. But I've also worked on industrial and infrastructure types of systems, and more than once I've seen someone say that they've got a cheaper solution to X, when really they've got something that may look cheaper if your only looking at upfront costs, but they are completely ignoring the lifetime costs of the solution.