The 2018 HPMS dataset encompasses the U.S. public highway system as of the 2018 calendar year, offering comprehensive insights into its extent, condition, performance, usage, and operational characteristics. Of particular significance to this research, it includes traffic volume estimates derived from state-collected traffic counts conducted annually, covering all highways, arterials, and collectors (classified as functional classifications 1-6). Traffic count data within the HPMS are gathered through a stratified, random sampling method aimed at achieving traffic count estimates meeting minimum precision standards, typically less than 10% error for at least 80% of roadway links (U.S. . The sampling rate varies by roadway functional classification and vehicle type, accounting for traffic volume variability across different regions, including states, rural, small urban, and urbanized areas. The HPMS does not encompass traffic volume data for low-volume roads in rural regions and minor residential streets in urban areas (classified as functional classification 7), which collectively represent an estimated 14.9% of the total U.S. traffic volume (U.S. . Table provides a comprehensive breakdown of total lane-kilometers and total vehicle-kilometers traveled (VKT) categorized by vehicle type and functional classification. The extensive dataset includes approximately 6.5 million rows (representing road links) and covers around 401,000 lane-kilometers, accounting for a total of 12.5 billion annual daily vehicle-kilometers traveled across the six roadway functional classifications. The HPMS provides an estimate of traffic volume from all vehicles as a single figure of AADT for each roadway link, also known as a roadway segment. On higher functional system roadways (generally lower volume roads), the HPMS requires less detailed data for MDV and HDV traffic. Tabulations of MDV and HDV AADT are provided for all interstate highway and national highway system links. For other roadways, HDV and MDV AADT estimates are available for a stratified random sample of roadway links, adhering to FHWA requirements (U.S. FHWA, 2016). These are designed to offer sufficient information to estimate MDV and HDV traffic volumes for each state, rather than for each individual roadway segment. The availability of MDV and HDV traffic volume estimates varies among states due to differences in the capabilities of their counting equipment and specific data requirements.