Chapter 3: Monitoring and Traffic Data Policy


Section 1: Traffic Monitoring Guide

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The Traffic Monitoring Guide (TMG) provides direction for improved statewide traffic counting, vehicle classification, and truck weighing. It was written to be a statement of good practice and is not to be considered a federal standard. The guidances provided in this document are meant to supplement other traffic monitoring guidelines for federal initiatives. The guide states that “data collection agencies are encouraged to consider the methods presented in their administration of a data collection program and to compare the cost-effectiveness of this methodology to procedures they presently use.”

The TMG provides detailed direction for using statistical procedures (sample size and sample frequency), which gives traffic data managers tools to determine what level of monitoring effort is required to achieve desired confidence and precision levels for their statewide traffic data. The design of the data monitoring system, as described in the guide, is interrelated and hierarchical.

A unifying element of the TMG is the concept of the direct, hierarchical relationship of the volume counts, vehicle classification, and truck weight measurements. Truck weight is a subset of vehicle classification, which is a subset of volume counts. Volume counts are a subset of the Highway Performance Monitoring System and so on until you reach the universe of roads.

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The TMG is used as guidance to improve the accuracy and precision of statewide traffic data through recommended data collection, analysis, and reporting methods. The guide contains several chapters detailing sample design for traffic monitoring, followed by detailed discussions on traffic volume monitoring, vehicle classification, truck weighing, and traffic monitoring data formats.

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Transportation Planning and Programming Division (TPP)

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Current Policy: Traffic Monitoring Guide, U.S. Department of Transportation, Federal Highway Administration, 1993.

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