Highway Deficiencies

Highway deficiencies come in at least three forms:

Mainline deficiencies

A mainline deficiency is a section of a controlled-access highway that does not live up to the standards generally expected on such a highway, and is split between Interstate highways and non-Interstate highways. An Interstate highway is considered "out of standard" if it does not, at a minimum, maintain the following:

• Full control of access (i.e. no traffic signals, at-grade intersections, pedestrian crossings).
• A minimum 50 MPH design speed (including curves and ramps which the mainline follows).
• A maximum grade of 7 percent.
• A minimum of two 12' wide traffic lanes in each direction, separated by a median.
• A 10' paved right shoulder (6' is acceptable in mountainous regions)
• A minimum 4' paved left shoulder
• A minimum of 14' clearance for overpasses.

Non-Interstate controlled-access highways are generally constructed to Interstate standards, but are not required to.  This is generally up to the state or local entity responsible for the highway.  For the purposes of this website, a non-Interstate highway is considered "out of standard" if it does not have the following:

• Full control of access (i.e. no traffic signals, at-grade intersections, pedestrian crossings).
• A minimum of two traffic lanes in each direction, separated by a median.
• A minimum of 2' shoulder or clearance on each side of the travelway.

"Super-2s" do not have the above lane requirement.  The mainline of a highway is defined by posted numbers, posted names, or any other form of identification widely used by the public.  The most popular is called a "Breezewood", named after the lack of full access control on a portion of I-70 in Breezewood, PA.

Junction deficiencies

A junction deficiency is a junction between two controlled-access highways that does not meet the standards generally expected at such junctions.  Examples include narrow lanes, short/nonexistent acceleration or deceleration lanes, traffic signals, side streets, and pedestrian crossings.

Partial interchanges

A partial interchange is an interchange between two controlled-access highways that does not directly support all possible movements. For instance, if at the interchange of highways 1 and 2, there is no ramp from NB 1 to EB 2, this interchange is partial. In some cases, signs direct traffic attempting the missing movement via surface streets, u-turn ramps, or the like.  At this point, this list does not include partial interchanges with local streets.

Multilane Interstates

This listing is somewhat separate from the Highway Deficiencies category, but is included here for reference.  The list shows those Interstates that maintain at least 6 through lanes for at least 5 miles or through 3 interchanges.  As the list is very incomplete, if you know of any Interstates that meet the criteria mentioned on the list page, please let me know.

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Page last modified 20 November, 2004