Chapter 1: Introduction

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Section 1: Overview of Manual

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Manual’s Focus

This manual provides instructions to traffic counters for:

  • Visually categorizing vehicles into specific classifications,
  • Manually recording counts of vehicle classifications into categories, and
  • Compiling counts and transferring the traffic data into designated forms.

This manual has been written to provide instructions to TxDOT personnel to manually classify, count, and record traffic data using safe and accurate procedures.

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Importance of Traffic Data

Traffic data is very important to many users. Transportation professionals use traffic data to plan, design, construct, operate, and maintain roadways. Decision makers use it to allocate funding for roadway projects, while other users decide where to build a hotel, estimate vehicle emissions, and more.

To collect traffic data, TxDOT uses short duration manual counts and automated permanent continuous counts. Some collection methods produce traffic volume, while others produce vehicle classifications. All methods are critical to developing traffic statistics, with one of the primaries being the Annual Average Daily Traffic (AADT).

Each data collection method has certain benefits and drawbacks. Automated counts can provide accuracy on high traffic, multilane roads that operate at a constant speed. Manual counts, the method taught in this instruction manual, use human observation to achieve accurate results in these situations:

  • diverse geographic locations
  • areas where vehicles follow closely
  • stop and go traffic
  • conditions requiring judgment (classifying a car pulling a light trailer versus a tractor pulling a semi-trailer).
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General Description of Work

TxDOT uses several different methods to collect information on the characteristics of traffic. This instruction manual specifically addresses the manual collection of vehicle classification counts. Technicians, referred to as traffic counters, must observe the classification of vehicles at specific roadway sites and manually record the traffic data for later use.

Traffic counters use a mechanical device to tally the number of vehicle classifications that travel past a designated site during a specific time period. In addition, the traffic counters report weather and road conditions for each hour of a scheduled count. TxDOT traffic analysts use the collected data to develop traffic statistics, which include the number of vehicles at given checkpoints, the percentages of vehicle classifications, and the directional flow of the traffic stream.

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Traffic Counters’ Requirement

Traffic counters must understand and follow the policies and procedures in this manual to safely and accurately conduct manual vehicle classification counts.

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