[ars]

Don't forget you need some kind of snow sensor - or at least a temperature sensor.

Or some kind of centralized switch.

Totally doable of course, but it does make them more complicated, more expensive and less reliable.

You would need to calculate the tradeofs. It's not automatic either way.

[Cushman]

A traffic light is already half of a snow sensor by virtue of being a light. If it's covered with snow, the snow will reflect light back. Add a few photoresistors and you're in business. It'd be the cheapest part of the whole project.