Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
52 Purpose: The Puget Sound Council of Governments (now the Puget Sound Regional Council) initiated the Puget Sound Trans- portation Panel in 1989 to track changes in household travel behavior over time (Kilgren n.d.). This was the first general pur- pose travel panel survey of an urban area in the United States. The information gained from the panel survey effort has been used to develop and refine the regional transportation model used for forecasting and analysis for transportation decision-making. A total of 12 telephone surveys were conducted between 1989 and 2002, with gaps ranging from six to 18 months between waves. The surveys varied, sometimes covering only demo- graphics and travel behavior (with travel diaries), and at other times including attitudes and values. Panel recruitment and maintenance: The panel was composed of approximately 1,700 households in King, Kitsap, Pierce, and Snohomish counties. Panel membership was recruited to include households with at least one regular bus rider, households with at least one regular carpooler, and households whose members drove alone for most of their trips (Kitamura 1989). During each wave, new households were recruited to replace households that were unable or unwilling to participate in that wave, or that could not be contacted. The replacements households were selected to mirror those who dropped out of the panel as closely as possible in order to maintain the same overall demo- graphic makeup of the panel. Additional attention was paid to the balance of people dropping out of the sample, representing out-migration from the region; and households that were new to the area, representing in-migration. The attrition rate for the panel was typically about 20%, but was as high as 39% when there was a gap of 18 months between waves. Documentation of the project available from the Puget Sound Council of Governments does not indicate that incentives were provided between waves. Lack of contact for periods of a year or more makes it more difficult to follow households who have moved between survey waves, adding to attrition rates. Implementation, analysis, and reporting: All members of the household 15 years and older were asked to complete a two-day travel diary, with some members also asked to complete a questionnaire on perceptions of and attitudes towards different modes of transportation. Benefits and disadvantages: Several advantages and dis- advantages of a panel approach were cited by the study. The advantages of panel surveys are: (1) direct measurement of indi- vidual changes; (2) ability to analyze causality about changes in place of residence, place of work, and commute mode; (3) smaller sample requirements for the same statistical reliability; and (4) lower on-going costs. The disadvantages of panel surveys are: (1) higher initial costs at empanelment; (2) possible higher non-participation rate; (3) attrition and replacement of panel member households; and (4) locating in-migrants to the region for recruitment. The first two advantages, taken together, are the greatest, because they permit causal inferences about the effects of changes in variables influencing behavior. When survey mea- surement is cross-sectional, using a different sample of survey households each time, the dynamics that affect travel mode are missed. Result: The panel survey program provided a rich and detailed source of mode choice and travel behavior data, including responses to changes in the transportation system. Information gained from the panel survey has aided in long-range transporta- tion forecasting and analysis used to inform decisions regarding highway and road construction and transit development, as well as carpooling and parking policies. The data has also supported special studies, including an analysis of the travel behavior of baby boomers. The project not only provided transportation planning data, it also provided detailed tracking of response rates, attrition rates, and other information that facilitates research about traditional panel research. The data is made available to the general public through an online custom survey data request form. aPPENDIX a Case Example of a Traditional Panel Survey: Puget Sound Transportation Panel
