# Accident modification factor

## Description

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## Variables

AMF | Accident modification factor (dimensionless) |

L_{c} | Length of the horizontal curve (dimensionless) |

R | Radius of the curve (dimensionless) |

S | spiral transition curves factor (dimensionless) |