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In this century, surface transport systems have become increasingly automobile dependent. Recent research challenges the assumption that increased automobile travel is necessarily good for an economy or society. Beyond a certain level, automobile dependency may impose more costs than benefits.  

Automobile Dependency
Automobile Dependency is defined as high levels of per-capita automobile travel, automobile oriented land use patterns, and reduced transport alternatives.
Highway advocates support increased construction of roadways, increased parking requirements, and low automobile user charges. They point out that motor vehicle travel is growing due to increased population, wealth and suburban lifestyles, resulting in increased traffic congestion. They argue that failing to expand roadway and parking capacity, and efforts to constrain motor vehicle use, contradict consumer preferences, stifle economic growth, and reduce personal freedom. They cite the general failure of public transit in the U.S. to attract new riders as evidence that highways are the most cost effective transportation investment. Highway advocates often argue that fuel taxes and other motor vehicle user charges should be dedicated to roadway improvements.

Transportation Demand Management (TDM) advocates support the development of a more diverse transport system. They recommend investing in travel alternatives and using a variety of Transportation Demand Management strategies, including higher user charges, to curb automobile traffic growth. They point to the high economic, social and environmental costs associated with motor vehicle use, and market distortions that result in excessive automobile travel, as evidence that increased motor vehicle use is overall harmful to communities. They argue that creating a more diversified transportation system is the most effective way to address traffic congestion, meet economic and social needs, support economic development, and protect the environment. They cite the tendency of "generated traffic" to fill new highway capacity, and the success of public transit and bicycle programs in some communities, as evidence that such alternatives are the most cost effective transportation investments. TDM advocates often argue that fuel taxes and other automobile user charges should be spent on travel alternatives, since motorists benefit indirectly from such investments, and because motor vehicle use does not pay its full costs.

Aide Memoire
"AUTOMOBILE DEPENDENCY: TOO MUCH OF A GOOD THING? Debating the Optimal Level of Automobile Use"
Double Session on the Economic and Social Impacts of Automobile Dependency Transportation Research Board 1999 Annual Meeting
Monday, January 11, 1998 8 a.m. to 12 noon
International East Room, Hilton, Washington DC
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