The guides: learn it once, keep it forever

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.

More are being written: the e-way bill and GTA GST, insurance decoded, the plate decoded, how the auctions work, and EMI with what lenders actually ask. If the one you need is missing, ask for it from the guides page and it goes on the list.