This report includes a detailed comparison of the TomTom national road grade database relative to a local road grade dataset generated by Southwest Research Institute and a national elevation dataset publically available from the U.S. Geological Survey. This analysis concluded that the TomTom national road grade database was a suitable source of road grade data for purposes of this study.
Wood, Eric,Duran, Adam,Burton, Evan,et al. EPA GHG Certification of Medium- and Heavy-Duty Vehicles: Development of Road Grade Profiles Representative of US Controlled Access Highways. 2015-01-01.