Transportation Planning Package (CTPP) at a cost of only $10 per 1,000 population or 1 cent per capita. Funding for the CTPP comes from funds available through ISTEA.

The census data on commuter travel flows and characteristics also are used to evaluate and select projects, develop traffic congestion management systems, and identify transportation corridors needing capacity expansion. Further, travel-to-work and vehicle availability data from the census for small areas are used by state and metropolitan planning organizations to prepare vehicular travel and pollutant emissions profiles, compute regional average rates of vehicle occupancy in the commute to work and evaluate the impact of long range transportation plans on air quality in compliance with the Clean Air Act Amendments of 1990. Finally, census data on the geographic distribution of persons with work disabilities and mobility limitations are used by local transit operators to provide service levels that are fully accessible to all segments of the population under the Americans with Disabilities Act.

The federal legislative initiatives cited above—the Intermodal Surface Transportation Efficiency Act of 1991, the Clean Air Act Amendments of 1990, and the Americans with Disabilities Act—delineate the national interest in rebuilding the transportation infrastructure, improving environmental quality, and providing a fully accessible system for accommodating the mobility needs of a diverse population. To respond to these statutes, policy and program development at the federal, state, and local levels needs to be based on decennial census data that provide a context for evaluating past trends and preparing forecasts of the future. The high levels of current use by both state transportation agencies and metropolitan planning organizations, along with the low cost of obtaining and disseminating the data lead to the conclusion that abandoning the tradition of nationwide survey uniformity and geographic consistency of data provided by the decennial census would result in high costs and disruption to program development and evaluation at all levels of government.

The continued collection of transportation data in the decennial census is under review. In response to congressional criticism, the Census Bureau is taking a zero-based approach to 2000 census planning. A major thrust of this approach is to question the justification for collecting data on topics such as place of work, mode of transportation to work, travel time, carpooling, time of departure for work, disabled persons with mobility limitations, and number of vehicles available to each household as part of the decennial census. This appendix reviews the history of the use of census data in transportation planning, the types of data available, and experience with the use of data in actual practice. Since the 1990 census results have only recently become available for transportation planning applications, much of this appendix deals with experiences with the 1980 census data. Discussion of the 1990 census is included wherever possible. The historical review of transportation data takes the perspective of building on the experience of previous censuses as has been its tradition in the past.

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