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# Horizontal Curve Formulas

This page shows the horizontal curve design speed formula to calculate the optimum speed or the safe speed for a vehicle to pass at a horizontal curve when V is greater or lesser than 50mph. The safe speed is given as V=(((-0.03 × r)+((((.03 × r) × (.03 × r))+((4 × r) × ((15 × (e/100))+3.6)))))/2), Where, V = Safe Speed for Horizontal Curve, r = Radius of Horizontal Curve, e = Super Elevation. For V is less than 50mph then, V = ((( -.015 × rhname ) + ( √ ((( .015 × rhname ) × ( .015 × rhname )) + ((4 × rhname) × (( 15 × ( ehname / 100 )) + 2.85 ))))) / 2). The horizontal curve formulas is essential for road construction engineers.

# Horizontal Curve Design Speed Formula

#### Formula:

If Safe speed of Horizontal Curve greater than 50 mph
Safe Speed for Horizontal curve ( V > 50mph ) = ( ( ( -0.03 × r ) + ( √ (((.03 × r) × (.03 × r)) + ((4 × r) × ((15 × (e / 100)) + 3.6))))) / 2)

If Safe speed of horizontal curve less than 50 mph
Safe Speed for Horizontal curve ( V < 50mph ) = ((( -.015 × rhname ) + ( √ ((( .015 × rhname ) × ( .015 × rhname )) + ((4 × rhname) × (( 15 × ( ehname / 100 )) + 2.85 ))))) / 2);

Where,

r = Radius of Horizontal Curve(ft)
e = Superelevation

#### Related Calculator:

Horizontal curve design speed formulas are necessary for gradual change in direction when a direct point of intersection is not feasible. Ex. Highways, Interstates, high speed roads with constant flow of traffic.