Cities don't build roads, but the pre-made maps are very large and have lots of areas that can develop, so buildings roads is not necessary. Road building is fairly expensive, because we wanted to guide players to rather develop the city by offering good transport options, but there's nothing to stop you from laying out roads to make a new suburb if you want to. The AI handles all the buildings, so there's no zoning or anything like that, because Cities in Motion is about public transport. I think a clever way to use the roads is to create shortcuts for your lines to use, like a bus-only road that lets your buses avoid the heaviest traffic.