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Summary of Recommended Standardized Procedures and Guidelines 29 2.4.9 E-13: Creation of ID Numbers Each completed survey requires a unique identification number. In addition, if data are retained on incomplete households, then all contacted households require a unique identifica- tion number. The primary issue with respect to identification numbers is that the numbers should permit ready retrieval of specific records and should provide a unique identification for each unit in the survey. In addition, there is the potential to provide some additional informa- tion through the identification number, such as the membership in a specific sampling category, thereby permitting easy checking of the sampling progress during the survey and ready identifi- cation for purposes of expansion and weighting after the survey is completed. These ideas are explored in detail in Section 7.9 of the Technical Appendix. It is recommended that 1. An ID number should be assigned at the outset to each eligible address or telephone num- ber in the contact list and this number should remain attached to the person or household for the duration of the survey. Telephone numbers or addresses that are established to be non-household numbers should not be assigned an ID number. 2. A stratification-based ID number should be used for all stratified samples, while date-based ID numbering should be used for surveys where sampling is performed by simple random sampling or systematic sampling. 2.5 Data Coding Including Geocoding 2.5.1 C-1: Geocoding Standards Geocoding is the process of identifying the geographic location of a trip end and coding a number--e.g., a traffic analysis zone (TAZ), census tract or block, or latitude and longitude-- to represent that location. This item is concerned with developing standards for the methods used to geocode travel data in household travel surveys. It is discussed at length in Section 8.1 of the Technical Appendix. It is recommended that All travel surveys should geocode trip ends to latitude/longitude. U.S. State Plane and other North American Datum coordinate systems (e.g., NAD27, NAD83) be used in geocoding unless there is a specific need to use another format. TIGER/Line files be used as reference databases for address matching. Information about frequently visited locations be collected and geocoded in the recruit- ment stages of a survey to maximize the opportunity to re-contact households to check addresses that cannot be matched. Geocoding for non-household and non-habitually visited locations be performed within a few days of data retrieval, also to allow households to be re-contacted if necessary. Respondents be asked for the names of cross streets and/or landmarks during data retrieval. Interviewers should have a good knowledge of the survey area or have access to gazetteers containing accurate addresses for shopping centers and schools. Online address directories (e.g.,, should be used to locate addresses in situations where supplementary information is not available. Pre-tests and evaluations should always be performed to assess the success of geocoding using one or all of the following methods: Aggregation checks on the location of geocodes; Checking addresses against other information such as telephone exchanges;