Cycled past this railroad crossing sign, but the tracks have long been removed on either side of the road.
I set up a discussion on Reddit, where the most likely explanation is the sign has to remain until the track is torn up and the road is repaved. Until then, there’s the possibility of mishaps (e.g., bicycles or snow plows) and the sign limits the liability.
The Exempt sign means busses and tankers don’t need to stop.
An alternative explanation is: leaving the track in the road maintains the legal right of way and increases the value of adjacent industrial land. Reinstalling track on the adjacent property is straightforward compared to all the hoops to jump through when establishing a right of way.
This was a high-quality discussion. The post has had over 100K views and 70 responses.