These data discrepancies are important to understand since, in the absence of fully comparable data (especially as regards travel distances), the report estimates traffic impacts on the basis of other data sources, including aggregate travel distance data gathered from ride service odometer data. In 2015 and 2016, they have been the leading source of growth in non-auto (i.e. non-personal car) travel in the city. They have also added significantly to vehicular travel and mileage on city streets.