Roadway Functional Classification

Roadway Functional Classification

"Functional classification is the process by which streets and highways are grouped into classes, or systems, according to the character of service they are intended to provide. Basic to this process is the recognition that individual roads and streets do not serve travel independently in any major way. Rather, most travel involves movement through a network of roads. It becomes necessary then to determine how this travel can be channelized within the network in a logical and efficient manner. Functional classification defines the nature of this channelization process by defining the part that any particular road or street should play in serving the flow of trips through a highway network."  (FHWA, 1989)

Road Functional Classes in Your Community

Roadway functional class can be used at the local government level to provide a direct link between transportation and land use.  Local comprehensive plans should consider the interaction between adjacent land use and transportation facilities by establishing policies that link access to property, zoning, and development density to the functional classification of area roadways.  A well-defined functional classification system in combination with designated truck routes can also be used to direct freight movements to appropriate facilities.

IDOT has developed an interactive map showing functional class designations regionwide to make it easier for residents to determine the designations of roads in their communities.  In addition, key route type and key route numbers of roadways can be looked up for use on IDOT applications (instructions). This information was drawn from the Illinois Roadway Information System, and is refreshed nightly to reflect current information.   In addition, IDOT publishes 5-Year Functional Class Township Maps in .pdf format.   District 1 includes the maps for northeastern Illinois.  You may look up your township name on the northeastern Illinois township map.

Reclassification of Federal Aid Routes

Over time, as development in an area changes, the function served by a roadway can change. CMAP developed a Functional Classification Revision Workbook to help communities navigate the process. 


1.  Who do I submit an application to?

Municipalities first submit their requests to their local Council of Mayor's Planning Liaison.

Once approved by the Council of Mayors, the Planning Liaison submits the application to IDOT.  The IDOT contact is Brian Carlson ( in the Bureau of Programming, District One.


2.  Where can I find the most up to date Functional Classification Map?

Use the IDOT web site -

  • Choose the Map Tab.
  • Click on "Map Type" and in the drop down menu, select "Roadway Functional Classification".
  • In the search box (upper right) type in your municipality, township or zip code.


3.  How can I produce the map for my Functional Classification Change submittal?

  • Zoom in or out of the IDOT FC map to capture your proposed route.
  • Make a screen shot of the appropriate portion of the map and edit it in an editable format.
  • Mark the proposed FC change with the color assigned for your desired functional classification by using in the editing tools.  See the functional classification guidebook for the appropriate coloring scheme.


4.  What is my street's FAU, FAS, FAP, etc. number?

FAU, FAS, FAP numbers are no longer used to depict route information, including functional classification or funding eligibility.  They also no longer appear on IDOT maps.  The key route designation is now used as the road's identifier.  The key route designation is the Key Route Type, a hyphen, and the Key Route Number available on IDOT's Getting Around Illinois map.


5.  Where can I locate the FHWA Functional Classification Manual and CMAP Functional Classification Workbook


6.  Who can I contact to ask questions about Functional Classification Changes

Top 5 Reasons for Denial or Delay of Revision Requests

1.  Using Funding as Justification for Upgrading the Functional Classification (FC) of a Road

Do not provide references to funding as the reason for the submittal.

  • In the application template.
  • In the letters of support.
  • In the resolutions.

Funding eligibility as justification will result in a denial or a request for new documentation. An example of an unacceptable justification:   "We would like to upgrade the road's classification so we can use federal funds for pavement improvements."  


2.  Not providing Letters of Support from Adjacent Municipalities & Townships

Many Functional Classification change requests take place on the border between different jurisdictions, such as municipalities & townships.

  • Letters of support are required from all affected jurisdictions.
  • When jurisdiction is in doubt, provide a letter of support / concurrence from the adjacent community or township (on their letterhead).

3.  Inadequate Spacing

Adjacent streets are being requested for Functional Classification upgrades from local to collector without adequate spacing within the Chicago Metropolitan Area.  

Information regarding appropriate spacing by functional class is available in the functional class revision workbook.

  • Are there exceptions to the spacing minimums in the workbook?  Clearly!
  • One way pairs of roads that operate jointly (i.e. "one-way couples").
  • Frontage roads & roads coming off of highway ramps.
  • Commercial areas that have large traffic generators.

The spacing in each submittal is reviewed on a case by case basis.  The specific roadway geometrics may allow one road's classification change to be approved with limited spacing and other requests that appear to be similar may be rejected.


4.  Not Connecting From a Federally Eligible Route to Another Federally Eligible Route

In general, when upgrading a local road to a collector, it should connect from one federally eligible classification to another.   Federally eligible classifications are: Interstates, Major Arterials, Minor Arterials, Major Collectors, and Minor Collectors in the urban area.  

  • No Dead-ends streets.
  • No endpoints for the Functional Classification change just because it is the municipal boundary.
  • Generally a roadway of higher classification should not terminate at a single roadway of a lower classification.
  • Avoid Loop Roads (roads that start & end on the same route) when possible.
  • Short loops never qualify.
  • Major loop boulevards through large subdivisions may qualify under rare circumstances.


5.  Not Providing Sufficient Justification in the Application and Letters of Support

  • The letters of support and completed application template are your opportunities to explain how the road functions differently than the surrounding streets. 
  • Review the definitions and other guidance and explain how the criteria apply to your roadway. 
  • An example of poor justification on a data sheet:   - "Roadway is justified based on Collector Criteria".   
  • Consider how the route will be functioning in the next five years.

Provide information on new development of major traffic generators impacting the road, such as:

  • Schools
  • Shopping centers
  • Office complexes
  • Large places of worship / community centers
  • Large parks
  • Large apartment complexes or subdivisions

Identify the other factors impacting the road, such as:

  • At-grade railroad crossings or grade separated crossings
  • Bridges, streams, and rivers
  • Bus routes
  • Traffic signals
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