Turnout Fit: Will This Car Make a #N Turnout?

A turnout’s diverging route behaves like a tight curve — the lower the frog number, the sharper it is. Pick the car you run and the turnout number for a straight FITS or BINDS answer, so a long car doesn’t pick the points or climb the frog on the branch.

A turnout’s diverging route is modeled as an equivalent “substitute” curve radius (approximate — brands vary); the car’s governing minimum is whichever is more restrictive of coupler-limited (= coupler overhang / sin(swing allowance)) or a length-based guideline. Frog angle = 2 × atan(1 / 2N). Confirm a marginal fit by rolling your longest car slowly through the branch. To check a plain curve instead, use the Minimum Radius tool.