coal mines!

coal mines could be an interesting environment for players to drive through or to just add to the level to add to the 19th century feel.

i like how these tracks lead to two tunnels. if cars were driving through it could give the player a choice of where to go. there appears to be some boxes in the way of the right tunnel. this could trap players and they could possibly drive down there by mistake or pushes down there as the openings are pretty narrow.

cars could maneuver between gaps in the architecture of this asset if certain parts were removed. 

the terrain to this type of mine could be very "bumpy" for a player to drive over and make controlling the car more difficult adding challenge.