When I built a minecart system for sorting villagers what I expected to happen was I could park the villagers on unpowered rails, like in minecraft 1.8
However they seem to move randomly, going off unpowered rails and even up slopes

Steps to reproduce:
1. in a creative single player world (also happens in survival) spawn a villager
2. place a minecart on some tracks and coerce the villager into the minecart
3. push the cart onto an unpowered gilded rail that leads into a wall
4. wait. You'll see the villager move the cart at about the time the villager's idle walk cycle begins.