What is the maximum superelevation rate recommended by AASHTO for conditions with snow and ice?

The maximum superelevation rate recommended by AASHTO for conditions with snow and ice is 8%. The rationale behind this guideline is to ensure that roadways are safe and suitable for vehicles during adverse weather conditions such as snow and ice. A superelevation rate higher than this could lead to excessive lateral forces acting on vehicles, potentially leading to loss of control on slippery surfaces.

A superelevation of 8% balances safety and operational effectiveness by allowing for sufficient drainage of water while minimizing the risk of skidding. It also considers the reduced friction available between tires and icy or snowy surfaces, making it crucial that the roadway geometry maintains a manageable superelevation rate during winter conditions. This approach helps enhance stability for vehicles navigating curved paths while maintaining safety standards for all road users in inclement weather.