Superelevation Improvement

Image Source: Google Earth

DEFINITION AND DESCRIPTION

Superelevation promotes motorist comfort as they accelerate a vehicle through a curve. Superelevation may be inadequate due to long-term deterioration from settlement or pavement overlays, or because the roadway was originally constructed prior to common use of superelevation. Superelevation may be inadequate due to design errors, lost over time due to settling, pavement overlays, or mistakes made during the original construction. Curves with inadequate superelevation may increase crash risk. Safety can be enhanced when the superelevation is improved or restored along curves where the actual superelevation is below optimal levels.

Implementation Categories

CONSIDERATIONS

• Increasing superelevation to improve motorist comfort may result in higher speeds.
• The slope break between the edge of pavement and the adjacent shoulder should not exceed 8 percent.
• Maintain a sufficient grade along the superelevation transition to provide sufficient drainage where the cross-slope approaches level.
• Improving superelevation is a KYTC SHSP Engineering Strategy.
• Often requires additional right of way.
• Improving superelevation during resurfacing can be a complex process, increasing both project cost and construction time.
• Statewide superelevation data are available.
• Coordinate improvements with curve signing, markings, and other countermeasures for consistency.

APPLICATION

• May be applied on high-speed facility curves that lack adequate superelevation and exhibit poor safety performance.
• Priority should be given to locations with a history of roadway departure crashes.

example

complementary SSA Strategies

• Curve Widening
• Increase Use of Roadside Barriers and Terminals
• Supplemental In-Lane Pavement Markings
• Sequential Dynamic Chevron Warning System