Roads not roads per cart efficiency
I've noticed on ramps that it detects the underlying blocks and adjusts the performance of whatever vehicle (hand carts are all I have used so far- the big powered vehicle is too big for me to comfortably use) i'm using rather than the kind of ramp i'm using. So when I go up my stone ramp, I get the notice i'm going over dirt or stone or whatever and i'm slowed to 50% efficiency. Is this something we need to contend with or is it a bug?
It's a bug
Best fix for this atm is to tamper the road under the ramps.