both pave and cultivate change the terrain that you had carefully leveled. Its frustrating, but minor. There is no reason you should not get a cart over paved road, the change is 'not flat' but its 'flat enough' for that. What I do is put down floor tiles and get it leveled to the same plane over a large area, or a line of them for a road. There isnt much practical incentive to pave a long road; it looks nice but flat dirt is better (smoother) for a cart.