Market sizing: total fuel burned by passenger vehicles on U.S. roads

You are asked for a back-of-the-envelope estimate of how much fuel the cars in the United States burn. Build it from first principles: write down the equation, state each input as a round-number assumption with a short justification, do the arithmetic out loud, and sanity-check the result. ```hint Start from one typical car Work out how much fuel a single typical car uses over a period from the distance it covers and its fuel economy. Then decide how many such cars there are, and whether every car deserves the same numbers. ``` ### Clarifying Questions - Which vehicles count: personal passenger cars only, or also the SUVs and pickups people drive as personal vehicles, taxis and ride-hailing cars, buses, government fleets and freight trucks? - Which fuels count: gasoline and diesel only, or should electricity used by electric cars be converted into a fuel equivalent? - Over what period, and in which unit: per day or per year, in gallons, liters or barrels? - Is this about current consumption, or a forecast for a future year? ### What a Strong Answer Covers - Scope settled up front: which vehicles, which fuels, what period and what unit - A clear equation linking the number of vehicles, distance driven and fuel economy, segmented where those inputs differ meaningfully - Each input stated as a labeled round-number assumption with a one-line rationale - Correct arithmetic and unit conversions, ending in one number and a plausible range - At least one independent sanity check and a note on which assumption the result is most sensitive to ### Follow-up Questions - How would the estimate change ten years from now if electric cars made up a large share of new sales? - Roughly what share of this fuel goes to ride-hailing trips, and how would you estimate it? - Which input would you research first to tighten the estimate, and why? - If the prompt were only to estimate the gasoline used in one 24-hour day, with no place and no type of vehicle named, how would you choose the scope (a city, a country or the whole world) and decide which fuel users to count?