The legal rules in the individual states partly order a warning triangle to be brought in the vehicle (in Germany according to § 53a StVZO).
The warning triangle consists of three reflective beams, similar to a cat's eye, and a stable foot.
If the vehicle is removed from the breakdown site, the warning triangle must be collected; it is not allowed to leave it standing.
Paragraph 7.3 of the traffic regulations: In the absence or malfunction of an alarm system on a towed mechanical vehicle, an emergency stop sign must be fixed on its rear part.
Under the Australian Road Rules, all heavy vehicles (GVM over 12 tonnes) must carry 3 portable warning triangles which comply with AS 3790.