Superelevation
This concept deals with the horizontal or lateral (cross) slope of a roadway. Superelevation of a roadway is used in order to accomplish two objectives: to provide adequate drainage flow for water on the roadway surface and to aid in steering of motor vehicles on curved roadways.
In a tangent section, a common superelevation or cross slope of 1-2% is applied in order to achieve drainage flow of surface water off of the subject roadway.
In a curved section, calculated super elevations generally reaching a maximum of 6 or 8% (depending on selected design criteria) are applied in order to aid motorists in safely traversing these sections while maintaining entry speed of the vehicle along the length of the curve.
Cross Slope
In a tangent section, a common superelevation or cross slope of 1-2% is applied in order to achieve drainage flow of surface water off of the subject roadway.
In a curved section, calculated super elevations generally reaching a maximum of 6 or 8% (depending on selected design criteria) are applied in order to aid motorists in safely traversing these sections while maintaining entry speed of the vehicle along the length of the curve.
Cross Slope
The maximum algebraic difference in cross slope between same direction traffic lanes of divided highway roadbeds should be 4%.
The maximum difference in cross slope between the traveled way and the shoulder should not exceed 8%. This applies to new construction as well as pavement overlay projects.
The American Association of State Highway and Transportation officials (AASHTO) provides a table from which desired superelevation rates can be easily interpolated based on the prescribed magnitudes for both design speed and radius of a curved section of roadway