How is superelevation transitioned on highway curves?

Superelevation transition occurs over a runoff length where pavement cross-slope changes from normal crown to full superelevation. Methods include: rotating about centerline (most common), inner edge, or outer edge. Transition typically starts 60-80% before PC on the tangent and continues into the curve. Spiral (transition) curves are often used to provide smooth change in curvature simultaneously with superelevation. Length depends on design speed and rate of change of cross-slope for driver comfort.