Compound Curve Solver

Enter R1, R2, I1, I2, and one known station. The solver computes PC, PCC, PI, PT, common tangent, common chord, curve lengths, and the vertex station automatically.

Inputs

R1 radius (m)

R2 radius (m)

I1 angle (degrees)

I2 angle (degrees)

Known station

Curve direction

Decimals

PC station--

PI station--

PT station--

PCC station--

Known inputPC station = --

I1 is the intersection angle of the first curve and I2 is the intersection angle of the second curve. The common tangent is T = T1 + T2.

Illustration

Total central angle--

Common tangent--

Curve length--

Back tangent to vertex--

Ahead tangent from vertex--

Common chord--

Summary of Formulas

T1 = R1 tan(I1 / 2), T2 = R2 tan(I2 / 2), T = T1 + T2

L1 = pi R1 I1 / 180, L2 = pi R2 I2 / 180, PT = PC + L1 + L2

x / sin I2 = y / sin I1 = T / sin(180 - I1 - I2)

The vertex is the PI of the back and forward tangents. For the example R1 = 400 m, R2 = 300 m, I1 = 36 degrees, I2 = 50 degrees, and PC = 4+509, PT is 5+022.127 and PI is 4+846.198.