In order to fit the ever increasing population into the same size areas, we have been growing our cities vertically for decades. However, we are still doing so based on the same old two dimensional zoning structure. We should modify the zoning laws to allow for vertical cities. Construct city high-rise buildings with multiple zones inside. So people can move from residential to commercial, to park, to school zones all by utilizing the elevators and stairs. This would reduce the number of people who need to utilize the transportation system and therefore the number of vehicles consuming various types of energy. Instead of trying to find out how to get people to and from the different parts of the city, we could bring those parts of the city to them.