Superelevation Variables
and Formulas

Use the following set of variables to calculate transition distances.

{e} | The full superelevation rate. This rate is determined from the superelevation rate table, based on the design speed and curve radius. |

{t} | The value that is read from the transition length tables, based on the design speed and the curve radius. In most cases, such as AASHTO, this is the transition length value from Level Crown to Full Superelevation. However, this value may not be an actual length, but some other value, such as a transition rate from which the length can be calculated. |

{c} | The unsuperelevated normal lane slope (positive). This value is defined by the user in the Calculate Superelevation - Lanes Page. |

{s} | The unsuperelevated normal shoulder slope (positive). This value is defined by the user in the Calculate Superelevation - Shoulder Control Page. |

{w} | The normal width of the traveled way. This value is defined by the user in the Calculate Superelevation - Lanes Page. |

{l} | The length of the spiral, if a spiral is involved in the transition. This is the actual length of the spiral element in the curve group. |

{p} | The fractional part of the transition length before the start of the curve or after the end of the curve. |

{q} | The rate of increase of centripetal acceleration traveling along a curve at a constant speed. |

The variables in the previous table are used to calculate the following:

The following table describes the formulas: