HIGHWAY PERFORMANCE MONITORING SYSTEM TRAFFIC DATA FOR HIGH-VOLUME ROUTES: BEST PRACTICES AND GUIDELINES

The primary purpose of the Highway Performance Monitoring System (HPMS) is to serve data
and information needs to reflect the condition and operating characteristics of the nation’s
highways. HPMS data support the analyses needed for the biennial condition and performance
reports to Congress. One of the required data elements for the HPMS program is vehicle-miles
traveled (VMT). VMT is derived from average annual daily traffic (AADT), so an accurate
measure of AADT is essential. Traffic data collected on the highest volumeroutes have the most
significant impact since these data represent a large share of total statewide and national travel.
These routes are also often the most difficult locations to monitor. State and public agencies use
various strategies to develop effective counting programs at these locations.
The objective of this project is to investigate and document information that can be shared with
states on various procedures being used to estimate and report traffic dataon high-volume routes.
This study focuses on the accurate collection of traffic data on high-volume routes, as well as the
processes that accompany the collection of these data. The study develops best practices and
guidelines for improving the quality of AADTestimates on these high-volume routes.