Compound Curves in Engineering Survey

Definition:

Combination of two or more simple circular curves of different radius having their curvature in the same direction. Essentially, a compound curve consists of two curves that are joined at a point of tangency and are located on the same side of a common tangent. Though their radii are in the same direction, they are of different values.

tr= perception/reaction time (seconds)
f = AASHTO stopping friction coefficient (dimensionless)
G = roadway grade (dimensionless)
e = super-elevation,
fs = the coefficient of side friction,
g = the acceleration due to gravity (=9.81 m/s2) and
v = the vehicle speed.
m = distance from center line to sight obstruction
L = length of curve
S = sight distance (ds)
R = Radius of center line
Rv =Radius to driver’s eye (middle of lane)
T = Tangent Length
C= Length of Chord (Long Chord from PC to PT)
E= External Distance
M = Middle Ordinate
Delta = Deflection Angle