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I~g <br />mortgage. Location Efficiency analysis is already being extended to allow LEMs in Seattle, <br />Washington and Portland, Oregon. In neither of these are mileage readings for vehicles available. <br />The dominance of Veh/Hh in the calculations of VMT/Hh facilitated these extensions. Veh/Hh, <br />available from the U.S. Census in all cities, along with densities, income, household size, transit <br />service and pedestrian and bicycle friendliness, allow the Veh/HIi equation to be calibrated. <br />Average VMT/Veh is calculated by state departments of transportation based upon fuel use, <br />screenline monitoring and other gross measures. This allows the VMTNeh equation to be <br />calibrated to the regional average VMT/Veh. <br />Extending the analysis to other important dependent variables -.vehicle trips and vehicle starts - <br />would require localized measures of these. The closest available measures are household travel <br />surveys, but as with VMT analysis these contain insufficient data. For instance, in the San <br />Francisco region there average less than ten households per zone. The scarce data problem is <br />aggravated by the lack of any households in many zones, especially the denser zones, which are <br />scarcer to begin with. Since fewer trips commence in denser zones, and are consequently less <br />critical to transportation planning, planners have tended to slight them. But aggregating zones by <br />residential density provides more respectable household numbers, allowing derivation of a gross <br />relationship of trips to VMT by residential density. This relationship could be used to extend the <br />predictions of VMT/Hh to trips/household. Similarly, the time between trips, if reported in the <br />household travel survey, could be used to extend the predictions to cold starts. <br />Similarly, the impacts on trips and VMT of job and commerce concentrations could be estimated <br />by use of household travel surveys. Jobs and local shopping employees are known by zone. <br />Grouping the zones by local shopping density or job ranges would allow shopping trips <br />10 <br />