Geocoding: a Necessary First Step

the 1950s, are a common tool for transportation planning. While these surveys are designed for the purpose of developing input for the travel forecasting process, the resulting data often end up being used for a wide range of planning and research activities. Stopher and Metcalf ’s survey of 55 recent travel surveys found that most took the form of a travel diary.1 While these diaries ranged considerably in format, one common element was a request that the respondents list the addresses associated with each trip or activity. This particular element is important insofar as it allows each respondent’s travel pattern to be geographically located and tied to a spatial database. Travel is an inherently spatial activity; therefore, the ability to explore travel patterns within a spatial database allows for a more complete exploration of the travel-diary output. A geographic information system (GIS) is the software that organizes, manipulates and analyzes such spatial databases. This feature discusses the benefits of using a GIS to process and explore traveldiary data. The application of a GIS to travel-diary data is illustrated by means of an analysis of a travel diary conducted in three neighborhoods in the Seattle, Wash., USA, metropolitan area. This 1992 travel-diary survey, the purpose of which was to examine the relationship between transportation and land use, collected data on two consecutive days of travel for 900 households. At an average cost of $400,000, travel surveys are an important, but costly, source of data.1 The high cost of travel surveys has made GISs an increasingly popular means of deriving maximum benefit out of this type of investment.