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1.0 Introduction

1.1 Background

The Federal Highway Administration (FHWA) is responsible for assuring that adequate highway transportation information is available to support its own functions and those of the Administration and Congress. The primary purpose of the Highway Performance Monitoring System (HPMS) is to serve these data and information needs to reflect the condition and operating characteristics of the nation's highways. The HPMS program is a cooperative effort involving state highway agencies, local governments, and metropolitan planning organizations (MPOs) working in partnership to collect, assemble, and report the needed data and information. FHWA maintains data submittal software and analytical models and techniques that can utilize the HPMS data to conduct the necessary planning and programming.

The data needed by the FHWA include highway length, lane-miles, and travel data to support the apportionment of Federal-aid highway funds under the Transportation Equity Act for the 21st Century (TEA-21). HPMS data also support the analyses needed for the biennial condition and performance reports to Congress and are the source for much information used in a variety of publications and media.

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. To report VMT for the HPMS, a jurisdiction must be able to count and classify vehicles accurately, use the count data to estimate AADT, and it must have a reasonably accurate total of its centerline-miles of highways.

Traffic data collected on the highest volume routes 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.

There are several possible sources of traffic data for high-volume routes that are not being fully utilized. Data collected by other agencies for other purposes, although supported by FHWA programs, are not always used for a variety of reasons, including accuracy, reliability, reference to HPMS section locations, and data management. However, states are using successful procedures that are not widely shared or even shared internally with appropriate state HPMS and traffic monitoring staffs. As a result, the best methods available to estimate AADTs and alternatives for improving data quality for HPMS are not being fully utilized.

1.2 Project Objectives

The primary 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 data on high-volume routes. This information will help improve HPMS traffic monitoring programs in urban areas. 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 will yield a report of best practices and guidelines for improving the quality of AADT estimates on these high-volume routes.

1.3 Organization of Report

The remainder of the report is organized as follows:

  • Chapter 2 presents the research approach and discusses the major findings from the literature review and interviews. These include issues and challenges associated with traffic data collection on high-volume routes
  • Chapter 3 presents the best or most common practices used by states to collect and process traffic data on high-volume routes. The practices were identified through a combination of literature reviews and interviews.
  • Chapter 4 presents the range of equipment used for data collection with a focus on advances in technologies and applicability for high-volume routes.
  • Chapter 5 presents the guidelines for data collection for high-volume routes. These guidelines are based on the practices and equipment discussed in Chapters 3 and 4. The guidelines are illustrated with examples with additional supporting documentation on a CD accompanying this report.
  • Chapter 6 presents the concluding remarks.

To maintain a manageable document size, additional documentation about practices are also provided on an accompanying CD. These include detailed documentation on traffic monitoring guidelines, contractor specifications, data quality guidelines, equipment evaluations, and performance specifications.

A user guide to the CD is provided as an appendix to the document. Sections with references to documents on the CD include hyperlinks in the main text of the report to the corresponding documents.

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