Sometimes I try things to see if I can do them. This is one of those cases, and I wondered if I could get a railway tunnel effect to work.
It is a matter of turning off the track rendering, and the display of the vehicles.
Using a new version of LittleBoB I set the tunnel height to 200 feet
The engine is about to enter the tunnel:
Here it has emerged a little later on:
I succeeded but it remains a novelty, because to make it realistic I would need somehow to get the exe to generate a tunnel graphic at the entrance and the exit
Just to save some time to get the screenies I made the train run at 140 mph, and sent the rest of the squad back to home base so that they did not attack it LOL