Technology

This almost certainly wouldn't work in the United States but it does in Europe because Europe has loads of these tiny abandoned rail lines (often single track) that were built in the 1800s and then abandoned. They don't go anywhere particularly densely populated, you know because of the industrial Revolution causing everyone to move to the cities, so there isn't the demand for a full rail service. Meaning they're not going to spend the money upgrading the infrastructure to modern standards.

This means they can be used at relatively cheap cost. As long as the tracks are still physically present all they need to do is cut some weeds down and put these things on the line and they're good to go. It's a cheap project that a local municipal authority can handle without having to involve wider government.