Superelevation Calculator

Design optimal road curve banking to counteract centrifugal force for safer highways

Design Parameters

Default values based on selected standard
Quick Guide
  • • Superelevation helps counteract centrifugal force on curves
  • • Higher speeds require greater superelevation
  • • Tighter curves (smaller radius) need more banking
  • • Always check against design standard limits
Warning: The calculated superelevation exceeds the maximum recommended value for the selected design standard.
Superelevation Results

Superelevation Rate (e):

0.00%

Recommended banking slope

Centrifugal Ratio:

0.00

v²/gR ratio

Force Distribution

Superelevation Contribution:

0%

Side Friction Contribution:

0%
Road Cross-Section Visualization

Visual representation of the road superelevation

Superelevation Formula

The basic superelevation formula is:

e + f = v² / gR

Where:

  • e = rate of superelevation (unitless, often expressed as percentage)
  • f = coefficient of side friction (dimensionless)
  • v = vehicle speed (m/s or ft/s)
  • g = gravitational acceleration (9.81 m/s² or 32.2 ft/s²)
  • R = radius of curve (m or ft)

The formula is solved for superelevation (e):

e = v² / gR - f

Design Standards Reference

  • Maximum superelevation rate: 4%-12% (varies by climate/region)
  • Typical maximum: 8% for rural highways, 6% for urban streets
  • Minimum radius tables based on design speed and superelevation
  • Side friction factors decrease with increasing speed

  • Maximum superelevation rate: 7% (plain terrain), 10% (hilly terrain)
  • Minimum radius specified for different design speeds
  • Superelevation is applied gradually in transition curves
  • Friction factors range from 0.09 to 0.17 depending on speed