I think it would be nice if someone were to make actual road tunnels... actual tunnels that, like the train tunnels, cut through the baseboard and such. I've run into a lot of situations where there's a mountain or cliff that's too steep for a spline to go on, so I just make a tunnel for the rail, but the road can't go anywhere. I have to just blast out a path through the hill for the road or simply end it abruptly, so that looks pretty unusual. I think it would be a cool addition.