Caltrans GIS Data

State Highway Network

State Highway Network (SHN) and Postmile System

This State Highway Network and postmile GIS database has highway line and postmile point feature classes. Each record in the line layer represents a highway segment where the county, route, postmile prefix, and postmile suffix are the same, and each segment has a begin and end postmile. The postmile layer displays valid postmile points at 0.1 (1/10th) mile intervals.  Both layers were created based on Caltrans SHN data as of December 31, 2017. 

Last Modified: August 21, 2018


The State Highway GIS database are based on the TSN database, including relinquishments, as of February 2, 2016. Changes include updates to routes 111, 195, 225. NAIP 2014 imagery was used to identify and verify roadway alignments during the digitizing process.

Detail information on how to interpret the meanings of the code of attributes are provided within the layers’ metadata.


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 the GIS Data Management Branch 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: Transportation, Highway, State Highway Network (SHN), California
Credits: California Department of Transportation

State Highways (Segments):, size 10.1 MB
State Highways Postmiles (0.1 mile intervals):, size 12.3 MB

Extent: California statewide

Source data:

This GIS layer was created using the 2009 Census TIGER roads file. From the 2009 TIGER data, highways were extracted and modified using BING imagery and street maps from the ESRI base map extension.

Transportation System Network (TSN) database maintained by the California Department of Transportation (Caltrans) Traffic Accident Surveillance and Analysis System (TASAS) branch.