Accident modification factor
The safety of a horizontal curve is affected by the length of the curve, the curve radius, whether spiral transition curves are used, and the superelevation of the roadway. For a given curve deflection, crashes are more likely on curves with a smaller radius. Spiral transitions decrease crashes, and insufficient superelevation increases crashes.
The value of S is as follows: S = 1 if spiral transition curves are present, S = 0 if spiral transition curves are absent.Related formulas
|Accident modification factor (dimensionless)
|Length of the horizontal curve (dimensionless)
|Radius of the curve (dimensionless)
|spiral transition curves factor (dimensionless)