// multi-utility computation suite · offline · instant · precise
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eng.horizontal-curve-design Calculator
Calculates horizontal curve design parameters including radius, tangent length, curve length, and superelevation from design speed and deflection angle. Minimum curve radius at 60 mph is 229m for a 4% maximum superelevation — design speed directly sets the minimum geometric standards.
Inputs
Design Speed Kmh
Rate of movement. 1 m/s = 3.6 km/h = 2.237 mph.
Radius M
Distance from centre to edge of a circle. Radius = diameter / 2.
Tangent Length M
Linear measurement. Ensure consistent units: 1 m = 1,000 mm = 3.281 ft.
Lane Width M
Horizontal extent perpendicular to the length.
Results
central angle Δ (°)
The computed angle in degrees or radians.
curve length L (m)
The computed linear length.
stopping sight distance (m)
The computed distance or separation.
required superelevation e
The value at the specified point or condition.
V²/127R(f+e) ≤ 1
Reference formula or conversion factor shown for context.