Roadway engineering calculations you can audit.
Most online calculators hand you a number and expect you to trust it. These show the equation, the substitution, the assumptions and the section of the manual each value came from — so you can check the work before you rely on it.
Every step is shown
Not just the answer. The equation, your values substituted into it, each intermediate distance, and the result — for every calculation.
Every constant is cited
Assumptions carry a citation to the manual, edition and section they come from, and the citation links to the issuing agency.
Calculated and adopted are kept apart
Design tables publish adopted values, not raw equation output. We show both, and explain the gap rather than papering over it.
Nothing leaves your browser
The calculation engine is client-side. Your speeds, grades and geometry are never uploaded, logged or stored.
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Stopping sight distance
Design speed and grade to required sight distance, with reaction and braking separated, US and SI units, inverse solve for supportable speed, and the TxDOT and Caltrans adopted values side by side.
Vertical curves, intersection sight distance, horizontal curves and superelevation are next. Which one comes first depends on what people actually search for and what the feedback on each calculator asks for.