I’m not sure if this is a bug or an oversight or whatever, but when you deconstruct a tile of gravel road, what’s left is “a nothing”. It produces pebbles & rocks, but if you pick up/move those and 'e’xamine the tile itself, it says “That is a nothing.” The tile cannot be moved onto. Haven’t tried if you drive onto or over it - don’t want to mess up my ride.
I would think there should be dirt beneath and not just an empty void. Just thought I’d mention it.