There are probably few readers of the Gazette who also read the weekly periodical Commercial Motor, but it was a table appearing in an article in the latter which caught the author’s eye and provided the inspiration for the present work.

In recent years legislation has been introduced which requires that lorries carrying dangerous substances must also bear panels on which appear, inter alia, codes identifying the substances and giving an indication to the fire brigade of what action should be taken in the event that the vehicle is involved in a collision or other emergency. Examples of the codes are shown in Figs. 1 (a) and (b). The former is probably the most commonly seen code as it is that displayed on petrol tankers; the latter is a code seen on a vehicle carrying liquid nitrogen.