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About the Controlling Criteria

The following information supplements PDDM Section 9.1.3:

The following chart summarizes the ten FHWA controlling criteria with typical sources for the specific values. Actual values depend on the design standard chosen. Use this information to fill out the Highway Design Standards form.

GB designates the AASHTO Green Book (2011 version). NPS indicates the Park Road Standards. For NPS roads only use the Park Road Standards for the Design Speed, Lane Width, and Shoulder Width criteria. Use the AASHTO Green Book or applicable state or local standards for other criteria. (The standard values shown in the Park Road Standards are based on the 1984 Green Book and so are outdated).

A "High Speed" road is defined as having speeds greater than or equal to 50 mph [80 km/h] or a freeway. Note that only two controlling criteria apply for non-High Speed roads.

CriteriaHigh Speed OnlySourceExplanation
Design Speed GB Tables 5-1 & 6-1 & Section 7.2; NPS Table 1Minimum design speed met based on the functional classification
Lane WidthGB Tables 5-5, 6-5, 7-3; NPS Table 10Minimum lane width achieved based on functional classification and chosen design speed
Shoulder WidthGB Tables 5-5, 6-5, 7-3; NPS Table 10Minimum shoulder width achieved based on functional classification and chosen design speed
Horizontal Curve RadiusGB Table 3-7Minimum horizontal curve radius achieved based on chosen design speed and maximum superelevation rate
Superelevation RateGB Table 3-8 to 3-12Was the correct superelevation rate chosen for each curve? Identify curves with insufficient superelevation.
Stopping Sight DistanceGB Tables 3-1, 3-2, 3-34Is stopping sight distance available along the horizontal alignment and for crest vertical curves? Use k values to assist calculation.
Maximum GradeGB Tables 5-2, 6-2, 7-2Are all grades below the maximum grade?
Cross SlopeGB Table 4-1; NPS page 31Selected cross slope falls within the appropriate standard range
Vertical ClearanceGB Section 5.2.3, 6.2.3, 7.2.5Minimum value achieved
Design Loading Structural Capacity GB Section 5.2.3, 6.2.3, 7.2.5Is structural capacity achieved
Updated: Wednesday, October 13, 2021