From a land use perspective, satellite cities and urban infill development are the best ways to accommodate population growth while preserving open space and farmland. The alternative is urban sprawl.
Satellite cities, like those that circle Stockholm, Singapore, and Tokyo, typically have a population ranging from 30,000 to 250,000. These planned cities are surrounded by greenbelt areas and are connected to the greater metropolitan area by an efficient rail system.
Satellite cities differ from suburbs, subdivisions, and bedroom communities in that they have municipal governments distinct from that of the core metropolis and employment bases sufficient to support their resident populations.
Theoretically, a satellite city could be self-sufficient, but what occurs in the satellite city/metropolis constellation is a pattern of cross-commuting, driven by housing costs and urban economics. The jobs/housing balance rarely yields a 50/50 directional split in travel flows; however, establishing mixed-use satellite nodes, similar to a necklace of pearls, with good land use management and rail transit services can go a long way toward achieving such balance.
Critics of new cities argue that their cost of infrastructure is too high. But it can be argued that the cost of urban sprawl is higher, with hidden costs like traffic congestion, pollution, and loss of farmland included in the cost/benefit analyses. With the world population expected to surpass 9 billion by 2050, infill development alone will not come close to meeting future housing needs. A limited number of new medium-size and large cities makes sense in countries with extreme housing shortages.
All new cities, regardless of size, must be planned to minimize their impact on the environment. The planner must strike a balance among ecological, aesthetic, and human factors. The car-free solar city model was influenced by the work of Ebenezer Howard and Paolo Soleri, and more recently by the principles of new urbanism. The satellite solar city would be carbon neutral, powered by alternative sources of energy, including solar cells and thermal collectors, wind generators, geothermal power, and hydrogen. Private automobiles would not be allowed in the solar city. Emergency vehicles would have street access in a designated lane. All waste would be recycled or reused. And the cornerstone of the master plan would be affordable housing.
The needs of schoolchildren, the elderly, and people with disabilities can be met in car-free cities through high-density mixed-use development served by good transit and located near essential facilities, including markets selling locally grown produce. In addition, parents of schoolchildren can organize "walking buses" (children walking in groups to and from school with adult supervision). The walking bus concept originated in the United Kingdom in 1995 and has recently seen increased popularity in the United States.
People can be served by personal rapid transit (PRT), a system of fully automated electric vehicles carrying two to six passengers that provides private, on-demand, nonstop service on a network of small, usually overhead guideways. Stations are located off line to allow for uninterrupted flow and high throughput. Any limitation in single-line capacity can be overcome by distributing traffic across the network. The operating system is managed by software with synchronous control, similar to that used for air traffic control. Computer simulation models show that waiting time for service typically would be less than two minutes during peak hours. Passengers select their destination at the station with a touch screen, and payment is made with a smart card. Vehicles are launched from their berth when a safe route is clear.
The continuous evolution of PRT can be traced back to at least 1953. All the components have been proven in other systems; most are available off the shelf. A necessary forerunner to PRT was the development and application of automated forms of conventional rail or automated guideway transportation (AGT) such as the Lindenwold-Philadelphia line, the Tampa and SeaTac systems, the Duke University system, and many others worldwide. These systems have operated for decades without experiencing a fatality caused by failure in the automatic control system. Morgantown Rapid Transit, a quasi-PRT system linking West Virginia University and downtown, has been operating since 1973, logging more than 150,000 passenger-miles with no serious injuries.
While many sophisticated prototypes have been developed and demonstrated, PRT has only recently been implemented in a real-world application. There are many reasons for this, but the chief one is that, by the middle of the 20th century, combustion-powered automobiles had established an intractable hegemony in transit by altering the structure of so much of the built environment. Had PRT been advanced in a neutral environment, the outcome may have been different. In addition, first-generation PRT was stymied by cost overruns; flaws in design, engineering, and review; opposition from strong transit lobbies; and technical limitations. Computers as recently as ten years ago had not reached a level of performance at which they could handle a large number of vehicles on a complex network. The new generation of PRT technologies has elevated the viability of the concept. Pilot projects are underway at London’s Heathrow Airport and in Masdar City, Abu Dhabi.
PRT is not necessary for the construction of car-free cities, argues J.H. Crawford, an American/Dutch writer and theoretician. "Superlative passenger transport is the only foundation upon which a car-free city can be built," he wrote in his 2000 book Carfree Cities. "Fortunately, existing rail technology easily fulfills the need, and we even have the luxury of a choice between two excellent systems: a heavy-rail underground system (metro) or a surface tram system." For transport within the districts, most people would walk or bike. Door-to-door walking distance within the districts would not exceed ten minutes, he writes. For the very young, very old, and disadvantaged, Crawford proposes use of large-wheeled pedal tricycles for those with poor balance, as well as motorized wheelchairs, baby strollers, radio-dispatched pedicabs, and speed-restricted electric taxis.
Development of satellite cities and urban infill projects constitutes the best strategy to accommodate population growth while preserving open space and farmland. All new cities, regardless of size, must be planned to minimize their impact on the environment. As a model for the satellite city of the future, the solar city signals a paradigm shift from the fossil fuel age to the solar/hydrogen age.