CNHRPC Traffic Data Collection Program
Each year, CNHRPC conducts over 200 traffic counts at locations throughout the region. This data is used both by CNHRPC and New Hampshire DOT to generate reports that assist in decision making by local and state officials. CNHRPC also uses count data to calibrate and validate its traffic modeling program. CNHRPC conducts its counts each year from May-October. CNHRPC maintains historical records for many of these locations so that growth trends can be examined. This data, covering every count from 2010* to the present is available online. Included are yearly counts requested by NHDOT, as well any count performed at the request of CNHRPC’s member communities or for the purposes of CNHRPC transportation studies.
*Hourly counts are available for most locations in the database. Please contact CNHRPC for more information.
*Most counts were conducted by CNHRPC – a small percentage come from member communities, neighboring planning commissions, and the NHDOT.
*In the case of a discrepancy between the CNHRPC & NHDOT count data please utilize the figure provided by NHDOT.
CNHRPC Traffic Counts by Town
NHDOT Count Database
In addition to the count database maintained by CNHRPC, NHDOT maintains a significant count database as part of their Transportation Data Management System.
NHDOT publishes its counts in the Annual Average Daily Traffic (AADT) format. AADT is an adjusted traffic volume and is defined by NHDOT as the total two-way volume of traffic at a given location during a twenty four (24) hour period representing an average day of the year. When calculating AADT, NHDOT employs seasonal and axle correction factors. The seasonal correction factors account for seasonal variations in traffic. Axle correction factors are necessary because automatic traffic counting machines count traffic based on the number of set wheels (axles) that a vehicle has. The axle correction factor assumes that a certain percentage of vehicles have more than two sets of wheels.
The correction factor employed by NHDOT explains the difference in data sets between the CNHRPC and NHDOT traffic count figures at the same location.
To access NHDOT’s Transportation Data Management System (TDMS) please use the following link: