Horizontal Curve Formulas
D = Degree of Curve, Arc Definition
1° = 1 Degree of Curve
2° = 2 Degrees of Curve
P.C. = Point of Curve
P.T. = Point of Tangent
P.I. = Point of Intersection
I = Intersection Angle, Angle between two tangents
L = Length of Curve, from P.C. to P.T.
T = Tangent Distance
E = External Distance
R = Radius
L.C. = Length of Long Chord
M = Length of Middle Ordinate
c = Length of SubChord
k = Length of Arc for SubChord
d = Angle of SubChord
R =  L.C.   T = R tan(I/2) =  L.C.



2 sin(I/2)  2 cos(I/2)

L.C.  = R sin (I/2)   D1° = R = 5,729.58   D2° =  5,729.58   D =  5,729.58

 

2  2  R

M = R [1  cos(I/2)] = R  R cos(I/2)
E + R  = sec(I/2)   R  M  = cos(I/2)



R  R

c = 2R sin(d/2)   d =  kD


100

L.C. = 2R sin(I/2)   E = R [sec(I/2)  1] = R sec(I/2)  R
