MAKING IT USEABLE    Editing       Logical Edits

Various edit routines were implemented to check the consistency of the reported data and to identify reporting or entry errors. Actual responses for all variables were examined for reasonableness and consistency across items. Extreme values that were either impossible or unlikely were identified, and inconsistent data were corrected when possible. For example:

• Very long walking trips, very short airplane trips, and very long waiting times were examined to determine whether they were legitimate data or probable entry or reporting errors.
  
  
• Calendar dates outside the survey period were edited based on other reported or assigned dates for the household.
  
  
• Some extreme or inconsistent data values, which could not be corrected, were edited to missing values.
  
  
• Edit flag variables were added to the database to identify key variables that had received logical edits.
  
  
• The relationship between the reported time and distance for all trips was examined by mode. Obvious entry errors were corrected.
  
  
• Trips with impossible miles per hour (MPH) for the reported mode of travel (e.g., 20 MPH walk trips) were either corrected or edited by changing the reported time or distance to missing values.
  
  
• The travel party size computed by adding the number of household members and non-household members reportedly on the trip was also edited by mode for all trips.
  
  
• Reporting vehicle odometer readings was apparently difficult for many respondents. Many cases were noted in which the two reported readings were impossible (second reading less than first reading) or unlikely (over 100,000 driven in a few months). Many of these reporting or entry errors were obvious (e.g., reporting the tenths of miles on one but not both occasions) and were corrected.
  
  
• The reported miles specific vehicles were driven by a certain person during the year and the number of miles persons reported driving in all vehicles during a year were capped at a maximum value of 115,000 miles per vehicle and 200,000 miles per driver.

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