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.

• 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