Mission & What We Do

The Traffic Survey Group is the primary traffic data provider for the North Carolina Department of Transportation. It is the Group’s mission to provide statewide coverage of quality traffic data using innovative analysis and traffic data collection methods to support the planning, design, construction, maintenance, operation, and research activities required to manage the transportation system in North Carolina.

Annual Average Daily Traffic (AADT) Traffic Volume Map

An AADT is an Annual Average Daily Traffic volume for all lanes in both directions passing a point on the highway system. It represents the average of all days during the year with typical traffic conditions. An AADT estimate is generated using procedures that comply with the standards specified in the Traffic Monitoring Guide published by the Federal Highway Administration.

With more than 40,000 Portable Traffic Count (PTC) Stations located throughout North Carolina, Traffic Survey has adopted the following data collection schedule:

• Interstate and primary roads (US and NC routes) outside of urban areas are collected annually.
• Urban areas and Secondary Roads (SR) are counted on a biennial cycle; approximately half counted each year.

The AADT maps are published annually once the data is processed and analyzed for the entire state. The AADT Traffic Volume Maps are available online, as a CD, and as a paper copy.

Please note the following:

• Not ALL roads have PTC stations located on them.
• With the exception of Interstate, NC and US routes, NCDOT County Maps refer to roads using a four digit Secondary Road Number, not a road’s local name.
• To find the secondary road number with the road’s local name or to find the road’s local name with the secondary road number, use The Secondary Roads Database Lookup. This database will provide a cross-index of the Road Name and the Secondary Road number. Be sure to first select the County when searching the location of a secondary road number

Annual Average Daily Traffic (AADT) Traffic Volume Maps Shape File

All data is provided in Series ArcGIS format and are readily viewed using ArcView or ArcMap software. More information about this software and data format specification can be found at www.esri.com.

The point data represented in this file was not created using GPS equipment in the field. The data was digitized referencing the available NCDOT, GIS dotroads.shp file. The Latitude and Longitude coordinates that are provided in the data table are a re-projection of the originally digitized points.

• AADT File Attribute Table Content Description

Traffic Data Request

We encourage our customers to use our online AADT maps. Using these maps will enable our customers to receive AADT data when they need it. However, if you still need the assistance of our office, please contact our Traffic Data Request Line.

When requesting traffic data, especially AADT traffic volumes, please provide the following information: (see example below)

• County in which the request is located
• City or Town (if applicable) in which the request is located
• Nearest intersecting road to the request location

Example:

• Wake County
• City of Raleigh
• I-440 (location of the count request)
• SR 1005 - Six Forks Rd (nearest intersecting road)

Please do not use an address, block number, distance or GPS when describing location.

Turning Movement Data

A Turning Movement (TM) study is performed to identify the character of traffic flow at an intersection. Engineers and planners use this information to identify base year flows for traffic forecasting. In this searchable database you will be able to query the turning movement data available from the Traffic Survey Group.

Traffic Monitoring Programs:

The Traffic Survey Group (TSG) Organizes traffic monitoring activities based on the model provided by the Traffic Monitoring Guide (TMG) published by the Federal Highway Administration (FHWA). Activities are coordinated under the following three programs:

• Coverage Count Program - This program consists of statewide coverage of short-term (48-hour) Portable Traffic Counts (PTC). There are approximately 40,000 PTC monitoring stations located throughout the state. Data is collected on both state and locally maintained roadways throughout the state. These counts are factored into Annual Average Daily Traffic (AADT) volumes using seasonal and classification data from other TSG programs. The Primary Routes (Interstate, US and NC) are collected each year while the secondary routes are collected on a two-year cycle with half being collected each year. Stations located within North Carolina’s 18 major Urbanized Areas are collected on a two-year cycle, with nine urban areas being collected each year. Stations designated either as small urban (areas under 50,000 in population) or rural are organized and collected by county each year.

  Other elements of the Coverage Count Program include:

  • Seasonal data is collected throughout the state from a sample of PTC stations four to five times per year for the purpose of updating the assignment of all stations into their prospective seasonal groups. A station's seasonal assignment is one of the factors used in estimating AADT.
  • Interstate data is collected and analyzed using a combination of mainline control station and ramp station counts. Segments are estimated by balancing ramp volumes between each of the known mainline stations. AADT’s are estimated for interstate routes every year.
  • Portable Vehicle Class (PVC) coverage is a new product currently being developed at this time in order to support the growing need for this data type and to meet FHWA monitoring requirements. It is planned that PVC data will be collected for the standard FHWA vehicle classifications by hour over a 48- hour period throughout the state on a 3-year cycle. Traffic Survey has just recently started expanding the number of data collection sites to support this process and provide a comprehensive coverage of our Statewide Highway System.
  
  
• Continuous Count Program - This program consists of permanent traffic monitoring stations that are used to collect traffic data 24 hours a day and 365 days a year on a sample of roadways throughout the state. The data collected at these stations is used to generate seasonal factors for the Coverage Count Program, are reported to the Federal Highway Administration for trend analyses, Highway Performance Management System reporting, cost allocation reporting and to support pavement design research and project planning studies. These stations provide a comprehensive understanding of traffic flow characteristics at each location.
  
  
• Projects Count Program - Project Counts range in magnitude from a simple bridge replacement to a very complex regional transportation model and is scheduled in coordination with the customer. Traffic data is requested to support a variety of planning and engineering studies and provides traffic count services for traffic forecasting, research projects, area transportation planning studies, and work zone design studies. The data collected may include hourly volume, hourly vehicle class, manual class, and turning movement data. In addition, special projects are sometimes designed to suite the customer’s data need.

A Spatial Editing and Validation Process for Short Count Traffic Data

A research project that investigates spatial techniques to validate short-term traffic counts within an automated quality control process.

• NCDOT Research Project 2002-09

Prototype Demonstration of a Geographic Information System Application for the Seasonal Analysis of Traffic Data, Development of Seasonal Factors and Seasonal Adjustment of Roadways

A method for updating seasonal groups for traffic count locations using an ArcView Geographical Information System application.

Table of Contents Glossary Disclaimer Executive Summary Report DOTF1700

Attachment A Attachment B Attachment C Attachment D Attachment E Attachment F

• Federal Highway Administration (FHWA)
  • Highway Performance Monitoring System
  • Highway Performance Monitoring System Field Manual
  • Office of Highway Policy Information
  • Traffic Monitoring Guide
• NCDOT Traffic Volume Maps