Sample Adequacy of the HPMS Program: A Case Study in Oklahoma

Abstract: The Highway Performance Monitoring System (HPMS) serves as the primary database for assessing the condition, usage, and performance of the National Highway System (NHS). The Oklahoma Department of Transportation (ODOT) maintains nearly three hundred Continuous Count Stations (CCS) across the state for accurate traffic monitoring and for calculating factor terms that support short-term traffic counts. This study centers on evaluating the adequacy and spatial distribution of these Continuous Count Stations (CCS) across Oklahoma, aiming to determine if their placement sufficiently captures traffic patterns in diverse regions, including rural, urbanized, and other high-priority areas—as mandated by HPMS standards. By examining the geographic and demographic representativeness of the CCS network, this research assesses whether current station locations provide comprehensive coverage that aligns with the monitoring needs for each area type. Employing geospatial analysis, this study investigates if the current CCS locations meet the sample size criteria outlined in the HPMS Field Manual and identifies potential redundancies and deficiencies in station coverage. This examination also addresses possible gaps in ODOT’s data collection approach and Federal Highway Administration (FHWA) reporting, exploring both strengths and areas needing further enhancement. The results aim to provide ODOT with actionable insights into optimizing CCS deployment—such as adjusting station density and improving data reliability. It is anticipated this study could improve data collection practices and enhance ODOT’s HPMS traffic data programs.

Keywords: Highway Performance Monitoring System (HPMS), Continuous Count Stations, Traffic Data, Geospatial Analysis