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🛣️ Highway Curve Explorer
A car, a banked curve, a speed limit. Change the design speed, superelevation (banking), and side-friction factor and watch the minimum safe curve radius respond live — the same lateral-force balance that sets speed limits on every banked curve you've driven.
Design Inputs
Live Result
Minimum safe radius Rmin—
e + f (total lateral demand)—
Powered by the exact AASHTO superelevation formula
(engine/highway-curve.js) — the governing 127 constant is not
taken on faith: it's derived live from first principles (e+f=V²/(g·R) with
V converted from km/h to m/s), and independently re-verified before publishing
that minRadius() and maxSpeed() are exact algebraic inverses of each other.
Method
AASHTO Green BookR_min = V²/[127(e+f)] — lateral force balance on a banked curve, SI units (V km/h, R m).
Scope: maximum e and f are agency policy (varies by design manual and climate) — this tool takes them as direct input rather than assuming a jurisdiction's specific limits.