Caltrans GIS Data


Traffic Volumes (AADT)

The point GIS datasets represent the traffic volumes for all count locations on the California state highway system. Peak Hour, Peak Month ADT and Annual ADT are shown at each count location.

Data Created: December 13, 2011
Last Modified: April 19, 2019


This traffic volumes feature class containing Traffic Volumes (also known as Traffic Counts) on California state highway network. The traffic volumes data used to create this GIS file are from Caltrans Traffic Census database compiled by Caltrans Traffic Data Branch summarized annually.

Annual average daily traffic is the total volume for the year divided by 365 days. The traffic count year is from October 1st through September 30th. Very few locations in California are actually counted continuously. Traffic Counting is generally performed by electronic counting instruments moved from location throughout the State in a program of continuous traffic count sampling. The resulting counts are adjusted to an estimate of annual average daily traffic by compensating for seasonal influence, weekly variation and other variables which may be present. Annual ADT is necessary for presenting a statewide picture of traffic flow, evaluating traffic trends, computing accident rates, planning and designing highways and other purposes.


The maps and data are made available to the public solely for informational purposes. Information provided in the Caltrans GIS Data Library is accurate to the best of our knowledge and is subject to change on a regular basis, without notice. While Caltrans makes every effort to provide useful and accurate information, we do not warrant the information to be authoritative, complete, factual, or timely. Information is provided on an "as is" and an "as available" basis. The Department of Transportation is not liable to any party for any cost or damages, including any direct, indirect, special, incidental, or consequential damages, arising out of or in connection with the access or use of, or the inability to access or use, the Site or any of the Materials or Services described herein.


Tags: Traffic Volumes, Annual Average Daily Traffic, AADT, Traffic Counts, California State Highway
Credits: California Department of Transportation
Files: 2010 Traffic Volumes:, size 0.624 MB
2011 Traffic Volumes:, size 0.641 MB
2012 Traffic Volumes:, size 0.600 MB
2013 Traffic Volumes:, size 0.638 MB
2014 Traffic Volumes:, size 0.478 MB
2015 Traffic Volumes:, size 0.680 MB
2016 Traffic Volumes:, size 0.747 MB
2017 Traffic Volumes:, size 0.781 MB
Extent: California statewide
References: Traffic Data Branch: