My brother sent me a fascinating link the other day.
While SimCity 3000 is a game (designed to be fun) rather then a model (designed to be useful) it has enough verisimilitude to be worth considering. Skip to the end, and consider the city with the highest density, and it's transportation network--the city relies entirely on subways, and devotes zero surface area to roads.
Cars take up an enormous amount of land area. Insuring sufficient parking means that there are four or five parking spaces for every registered driver. A standard parking spot is running about 200 square feet, once you count landscaping and space to enter and exit the parking space. About the size of a small studio apartment.
SimCity provides a very interesting perspective on development and scale. Unlike the real world, which is developed by multiple independent agents, a SimCity effectively has a 'single developer', who has the perfect cooperation of all municipal entities. Decisions that make sense in the microcosm don't always make sense in the macrocosm.