Seats
seating counts the passengers only: the driver, an attendant and a conductor are left out. A maker’s “D+2” is 2, a bus’s “52+D” is 52, “Driver only” is 0. It is a whole number from 0 to 120. The site labels it “Seats (excl. driver)”.
Tyre size
tyre_size is one canonical headline: <width>[/<aspect>]<R|X|D|->[rim][LT|C][-<ply>PR], with no spaces. Inch widths under 10 keep two decimals (7.50X16-16PR), 10 and above are whole numbers (10R20); a metric size keeps its slash (295/80R22.5). A vehicle that runs two sizes joins them with / (10R20-16PR / 295/80R22.5-16PR). Words such as Tubeless or Radial are not part of the size.
To match a size, use the tyre_size filter on /variants, which reads every spelling the same way (7.50x16, 7.50 X 16 -16 PR and 7.50X16 are one size), or /tyre-sizes for the sizes on the register with their counts.
Fuel
fuel is one of diesel, petrol, cng, petrol-cng (bi-fuel), lpg, lng, electric, hydrogen, hybrid, or empty when the maker does not say.
Name
name is the maker’s own name for the variant, with nothing left out and never opened by the maker’s name: the maker travels beside it as manufacturer.name, so print the two together. A product family the maker sells under its own word stays in the name (King Deluxe CNG, ISUZU NQR (CHS)). The slug never changes once published.
Body types
body_types holds keys from one vocabulary (chassis_cab, cowl, open_deck, tipper, container, school_bus and the rest of the body_type facet on /taxonomy), at most six. A maker’s own word for a body the vocabulary does not hold is not a key: it is kept on the sheet, in the maker’s words, on the line “Body, in the maker’s words” of the body group in spec.
Class
vehicle_class is the register’s class: truck, bus, pickup, three-wheeler, tractor (the prime mover of a tractor-trailer, never a farm tractor), tipper or special. Farm tractors and construction machines are their own sections, on /tractors and /machines.