This is a plan for a sustainable city. Evidence suggests that less energy will be available to us in the future, which means that the energy-intensive suburban sprawl model which has dominated for the past 50 years is no longer sustainable. Even without energy constraints, urban sprawl no longer makes sense due to changing demographics (only 1/3rd of households are families with children). The technology to run cars on alternative fuels is not available at the scale required to keep urban sprawl running. If the world's cities continue to sprawl there is a danger that by the year 2050 when world population has reached 11 billion that all of the forests on earth will have disappeared. For all of these reasons, the only option left to us is to stop the horizontal expansion of our cities and to create more compact cities that do not rely on automobiles for transportation. The planet cannot sustain a detached house for every family and two cars in the garage, but sustainable cities can be built that can provide a higher standard of living for everyone.
What follows is a plan for a sustainable, compact city. I would be interested in anyone's thoughts, comments, or suggestions.
The Sustainable City:
-The city does not exceed 0.65 square miles for a population of 10,000. 6.5 square miles for 100,000. 65 square miles for 1 million, 650 square miles for 10 million, etc.
-Minimum residential density of 20 units per acre (15,000-16,000 people per square mile) The typical American suburb is 4 to 5 units per acre or 3,000-4,000 people per sq. mi. The density must be an average of 20 units per acre for the area within 1/2 mile of a mass transit stop. Due to the high density, most housing would be in apartment buildings. There would be few if any single-family homes, and these would be reserved for families with children.
-Every building in the city is no more than 1/2 mile from a transit stop. 1/2 mile is equal to a 10 minute walk at a comfortable pace. Some cities may wish to reduce the maximum distance from a transit stop to 1/4 mile, but this requires a higher minimum density.
-Commercial and public services are located adjacent to the mass transit stop. Each transit stop functions as a neighborhood center. There is a sufficient range of services at the center to meet all of a household's weekly needs
-Mixed-use buildings are permitted in or near the mass transit stop/neighborhood center
-Maximum building height of 6 stories. For the same size population, mid-rise buildings consume less energy than high-rises. The exception to this rule would be cities that do not have sufficient space to house their population in 6 story buildings.
-There are no surface parking lots. Parking is on-street adjacent to the curb and in garages. There are no off-street parking requirements. With everything in the city within walking distance of one's home, car trips would be greatly reduced making off-street parking unecessary and a wasteful use of space.
-Maximum street width of 26 ft (4 lanes). This is so that pedestrians can easily cross the street at any point. Also, vehicle speeds tend to exceed 30 mph on roads wider than 26 ft. Above 30 mph, a pedestrian's chance of survival if hit by a car is less than 50%.
-Streets are built in a modified grid pattern for ease of navigation. The grid may be modified to suit the terrain. This is so that it is easy to walk from one point to another within the city.
-Buildings are 10-40 ft from the street. Residential buildings might be set further back so that there is more space for grass, trees, and shrubs. Commercial buildings would be closer to the street as this has been shown to draw people into the store, and creates a stimulating streetscape to look at while walking (as opposed to acres of surface parking fronting the road).
-If there are multiple buildings fronting the same street, a building must share a setback with at least one adjacent building. This is so that buildings are not randomly scattered on a block.
-Trees are planted in or adjacent to the sidewalk for shade. This is especially important in hot climates.
-50% of the city's ground space is dedicated to parks/landscaping.
-Food may be grown in vertical farms where necessary. These have the advantage of not being affected by weather so crop yields would always be optimal. Since they are located in the cities themselves, the energy used in transportation would be eliminated, reducing costs and pollution. Vertical farms would be no taller than the rest of the structures in a city so they would blend seamlessly into the urban environment - in a typical compact city they would be no more than 6 stories tall.
-Each neighborhood would be allowed to draft its own plan. The only requirement is that the plan must fulfill the requirements of the compact city as outlined.