Maximum Curve Radii for Various Desired Speeds

Desired

Speed

Assumed

Side Friction1

Assumed

Superelevation

Maximum

Radius

• 15 mph

0.38

0.00

43

• 20

0.30

0.00

88

• 25

0.25

0.00

167

• 30

0.22

0.00

273

1Based on American Association of State Highway and Transportation Officials (AASHTO), A Policy on Geometric Design of Highways and Streets, Washington, D.C., 1990, Figure III-17 and Table III-17.

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