Radius from Degree of Curve

A "degree of curve" is a convenient way to describe how sharply a horizontal curve bends in road, rail, and canal design. The constant 5729.58 comes from converting the arc-based definition of degree of curve into feet and degrees, so the formula directly gives the radius of the circular curve in feet. A larger degree means a tighter curve, which is why the radius decreases as D increases.

Use this when a surveying or geomatics problem gives the degree of a simple circular curve and asks for the curve radius. It is especially useful in transportation alignment work for highways, railways, and site layouts where curve sharpness must be checked or designed.

• Using the formula with D in radians instead of degrees
• Forgetting that the radius is in feet only because the constant 5729.58 is based on that unit system
• Assuming this applies to spiral or compound curves instead of a simple circular curve