The shapefile provided for P6 Prioritization is the same data being published by the NCDOT to report 2018 AADT and VC statistics for HPMS and State uses. The data provided for P6 includes the Peak Average Daily Traffic (PADT) statistic developed jointly by NCDOT and the Institute for Transportation Research and Education (ITRE) at NC State University. In general, this statistic is an estimate of the monthly average daily traffic for the peak month of the year on a route. It provides an estimate of the relative level of demand experienced during a peak travel period. Refer to documentation developed by ITRE for more information regarding its development and methodology for estimating PADT. A PADT estimate is provided for all routes that are monitored for AADT except for ramps or federally owned routes.

The AADT & VC shapefile is a segment shapefile of Annual Average Daily Traffic (AADT) and Vehicle Class (VC) estimates. This data resource includes what has been submitted to FHWA for Highway Performance Monitoring System (HPMS) for AADT and VC data reporting for 2018. We report AADT on all highways functionally classified (FC) above Local. A full coverage is provided for these routes where AADT segmentation is based on network configuration, travel patterns, and land use. Data is provided for ramps also. The ramp data is not a complete segment coverage but all major traffic flows at interchanges are reported. Where divided highways occur, the AADT estimates are for both directions but referenced on the inventory direction. There are 31,144 traffic segments maintained (labeled “Maint” in the SOURCE field).

Supplemental AADT are provided on the routes that are Local FC. These are not maintained in the maintenance table described above. A reference was generated through a spatial join between the monitoring station point and the LRS Arc it falls on. The extent of highway this AADT represents has not been determined. This process captures the AADT for Local routes into the published table without requiring a comprehensive maintenance process. The AADT on Local routes may extend beyond the arc used to report it. The user must exercise their own judgment in determining the limits of an AADT in this case (labeled “Supp” in the SOURCE field). There are 16,186 references that are supplemented using this method.

VC data is provided for those segments where vehicle class data was collected. Truck volume data is collected at stations and the volumes are annualized. Annualized truck percentages for Single Unit (SU) and Multi Unit (MU) trucks are generated from this data. These truck percentages are applied to the 2018 AADT estimates to generate 2018 truck volume estimates. The truck percentage and volume estimates are provided in the shapefile. The VC coverage includes the National Highway System (NHS) and the NC Truck Network. VC data is not collected on routes not part of these systems and they do not have truck statistics.

The referencing provided is based on the 2019 Quarter 1 publication of the NCDOT Linear Referencing System (LRS) maintained by the GIS Unit. This is the official 2018 data set reported for HPMS routes, is the basis for the highway mileage reports, and was used to estimate vehicle miles of travel (VMT) for 2018. Differences in the arcs and references will be found when using other quarterly publications with this data set.

Attribute Table Fields

The traffic data provided is seasonally factored to an estimate of an annual average of daily traffic. The statistics provided are:

Data was manipulated specifically for P5, including removing attributes, renaming fields, and creating new fields. The fields used for P5 are as follows :

Rte_ID:GIS 11 digit unique route identifier

BegMP1: Route milepost at the beginning of the reference

EndMP1: Route milepost at the end of the reference

AADT:Estimated Annual Average Daily Traffic in vehicles per day for 2016

PADT:Estimated Peak Average Daily Traffic in vehicles per day for 2016

AADTT:Estimated annual average daily total trucks in vehicles per day for 2016

Truck_Pct: Estimated percentage of daily total trucks per day for 2016 calculated by AADTT/AADT

TruckPercent: Estimated percent of daily total trucks per day for 2016 calculated by AADTT/AADT * 100

The segment location data are suitable for relating the AADT/VC data with other data by:

1. Spatial association using the arcs

2. Event association by using the Route/Mileposts

If additional information is needed, or an issue with the data is identified, please contact Kent Taylor at (919) 218-4049 or email at kltaylor@ncdot.gov.