Functional Classification: On vs Off System

It can be confusing trying to figure out what type of road is classified as an “on” system road versus an “off” system road. And what’s the difference between the NHS and the Federal-Aid System?

I’ve finally found the answers, not to mention a few minor torturing tactics that I developed along the way to pry this information out of my colleagues. But that’s another blog entry for another day 🙂 I hope you find this information helpful.

on vs off system


Streets and highways are grouped into classes based on the service they provide. The California Road System (CRS maps) display functional classification which is used in determining funding eligibility, as well as applicable design standards.

Additionally, here is a breakdown on Functional Classification (FC) by numerical value. They are color coded as displayed on the CRS maps.

A breakdown of non-State Highway NHS can be found here or at the Caltrans NHS website.

The NHS includes the following:

  • The Interstate System.
  • Principal arterials (including those not previously designated as part of the NHS) and border crossings on those routes.
  • Intermodal connectors — highways that provide motor vehicle access between the NHS and major intermodal transportation facilities
  • STRAHNET (Strategic Highway Network) — the network of highways important to U.S. strategic defense
  • STRAHNET connectors to major military installations.


Below is an example of a CRS map.

crs maps example

For more information regarding Functional Classification, NHS or the Federal Aid System, please visit:



2 thoughts on “Functional Classification: On vs Off System”

  1. This is an excellent explanation! Being an ITS techie, I rarely need to know this – but there have been occasions where this would have save me a lot of time. One of them created a further question regarding these NHS definitions. Here’s your Quiz for today (based on a true story):

    A geographically-large city has a central traffic management center, which is connected to each of their 1000 signalized intersections by a large network of fiber-optic cables. Implementing this city-wide signal system required a number of fiber-optic Nodes (distribution hubs) that contain expensive electronics. This is “mission-critical” stuff! Rather than install these essential Nodes on the street (where they would be vulnerable to weather, crashes, theft, terrorism, etc.), the City chose (wisely!) to locate these Nodes inside of fire stations and other secure city facilities.
    As you have already deduced, the Nodes were not located “on” any public roadway ROW. However, their sole purpose was to serve the traffic signals located on City roads, with FC = 2 thru 7.

    How would you classify eligibility of the Nodes? (Choose the best answer.)
    a.) Not eligible – none of them are located on a public roadway ROW.
    b.) Partially eligible – based on the percentage of the 1000 signals on the NHS.
    c.) Partially eligible – a Node is eligible only if it serves a signal on the NHS.
    d.) Fully eligible – to synchronize NHS roads, cross routes must be controlled.
    e.) None of the above

  2. As a retired DLAE it’s my guess that FHWA would determine that all the nodes are eligible, providing they all contribute to the efficiency of the federal-aid system operation. We had a similar question 25 years ago regarding eligibility of bus stops – since some were located on side streets adjacent to FAS routes. The feds agreed they benefitted FAS system efficiency (by congestion mitigation) and could be included in the eligible project costs.

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