Functional Classification

Maranda Obray, Transportation PlannerIdaho Transportation Department

What is functional classification?

• A process by which streets and highways are grouped into classes, or systems, according to the function they are intended to serve.

Why classify roads?

• There are approximately 4,000,000 miles of roads in the U.S.

• Some are more “important” than others• Helps determine which level of government

has responsibility• Influences design• Affects how they are funded• Impacts Federal-Aid

Federally required

• Functional classification is a federal requirement, however:– It is just a guide – Varies in practice by state– Functional Class boundaries are not rigid– Some states develop supplemental criteria

• Don’t Over Think It!

What is the function of a road?

• Provides mobility (interstate/arterials)

• Provides access (locals)

• Provides both (major/minor collectors)

Federal-Aid Routes

• National Highway System– Principal arterials (Interstate, Other Freeways &

Expressways and Other Principal Arterials)• State Highway System

– Other Principal Arterials– Minor Arterials – Major Collectors

How are they determined?

• Group population centers and major travel generators

• Identify neighboring centers

• Connect the largest directly

• Connect the next group to the major centers

Interstate/Arterials

• Carry most of the traffic• Primary purpose is through traffic and direct

access is limited• Link cities and form an integrated network

providing interstate and/or inter-county service

• Examples: I-84, US-95, SH-20/26

Collectors

• Major – Serve shorter more localized

travel needs– Collect traffic from local

streets in residential neighborhoods and channel it into the arterial system

– May penetrate residential neighborhoods, distributing trips from the arterial through the area to the ultimate destination

– Examples: Indiana Ave., East Powerline Rd. and Roosevelt Ave.

• Minor– Provide service to traffic

generators within the county that are not directly served by the higher system

– Link these places with nearby cities, or with routes of higher classification

– Serve more important travel corridors within the county not served by arterials

– Examples: Apple Valley Rd., Homedale Rd. and Purple Sage Rd.

Local Streets

• Provide direct access to homes and businesses• Designed for low traffic volumes, the collector

and arterial system must be adequate, otherwise congested major streets may lead to drivers finding short cuts on local streets

Functional Class Codes

Putting it all Together

Future Processes

www.iplan.maps.arcgis.com/home

2025 Statewide Functional Class Map Deadlines

• December 1, 2013 – All submittals due to Idaho Transportation Department Headquarters for review

• February 1, 2013 – All submittals due to FHWA for pre-approval review

• April 1, 2013 – All proposed changes presented to the Idaho Transportation (IT) Board

• June 1, 2013 – Recommendation from IT Board• August 1, 2013 – Approval and Signature from FHWA

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