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In fact, one of the biggest problems that fast-growing regions in California and the rest of the nation face is that vehicle miles traveled (VMT) are rising at a much faster rate than population. According to the California Air Resources Board, the total annual VMT in this state “more than doubled between 1970 and 1990, increasing from 115 billion to over 250 billion miles of travel per year. During the same period of time, the State’s population grew by about 51 percent.” ["Land Use Air Quality Linkage" report, p.1] As different regions continue to grow, and people continue to spread out in low-density, disconnected suburban development patterns, this trend can only be expected to worsen. To slow down this increase in VMT will require finding ways to encourage people to use their cars less. One of the most effective ways to do this is to create communities in which residents can travel without using a car. These are typically compact, mixed-use communities which are friendly to pedestrians, bicycles and transit. Several studies have found that residents in these types of communities typically own fewer cars and drive shorter distances. As noted in the Air Resources Board's 1994 "Land Use Air Quality Linkage" report, a study on travel behaviors in several neighborhoods in the San Francisco Bay Area "concluded that for each doubling of density, the average VMT per person each year is reduced by 25% to 30%." [p.7] The same trend was found in a worldwide study of urban density, travel patterns and transportation facilities in 32 major cities according to the ARB report. To slow down this increase in trips and VMT — and improve air quality — will require finding ways to encourage people to use their cars less. One of the most effective ways to do this is to create mixed-use, compact, walkable communities. Those “livable communities” in which residents can travel without using an automobile usually include a range of housing types that are located conveniently near public transit, services, stores, and jobs. In order for communities to support neighborhood stores and transit, and provide a range of housing types and prices, it is necessary to create communities that are more compact than the typical suburban development. Large subdivisions of single family homes on quarter acre or larger lots simply do not provide the population density necessary to support a neighborhood retail center, let alone convenient transit service. The ARB notes that "clusters of medium-density residential areas that average 7-15 dwelling units per acre can generally support frequent local bus service. If such densities are maintained over a large enough area, with good pedestrian accessibility, then light rail transit service may also become feasible." ["Linkage" report, p.6] According to the Institute of Transportation Engineers, in order for even a low level of transit service (one bus per hour) to be feasible, a minimum overall density of four to six dwelling units per acre is needed. The frequency of service may be substantially improved if densities average at least 7 dwelling units per acre. Also, when development is clustered in medium densities averaging 7 dwelling units per acre, frequent local bus service becomes more cost effective. If higher average densities of over 9 dwelling units per acre are maintained over a large enough area, light rail transit service also can become feasible. ["Linkage" report, p. 6] |
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