The guides: learn a code once, read it anywhere

A commercial vehicle is sold and run on codes: a tyre's sidewall, a battery's label, an axle rating, the four numbers an electric truck is sold on. The guides decode them one at a time. Hover or tap a part of the code and the meaning lights up, so you learn the thing itself rather than memorising an answer.

They are free, need no sign-in, and are written for the road's own buyers rather than for an engineer. The tyre guide includes the date trick that old rubber hides behind; the battery guide explains why the stamp date is the bargain; the axle guide shows how overloading actually gets priced.

If the guide you need is not there, ask for it from the guides page. Every ask is read, and the guides asked for most are written first.