Transportation of dangerous goods is often done in a large transport truck or shipping container. There are regulations regarding signage for the outside of the vehicle or container, according to the ADR of the UK Health & Safety Executive. Put simply, these vehicles must show the ADR orange plates on the front and rear and any shipping container must also be labelled with these the correct class plates on all four sides of the container. When the hazardous materials are removed from the vehicle or container, the plates must also be removed to show that they no longer carry any dangerous material on board. These signage requirements are for the safety of handlers as well as any type of rescue service if the vehicle is involved in an accident.
Small vehicles, such as vans and small trailers, are exempt from the above requirements as long as they are carrying less than the thresholds outlined in the ADR regulations. This link can be followed to reach The UK Health & Safety Executive website: http://www.hse.gov.uk/cdg/manual/exemptions.htm. Whilst most smaller vehicle operators do not display the orange plates, they often put 100mm warning diamond labels on their vehicles, especially ones carrying compressed gas cylinders. They do this to indicate hazards that their goods could create.
Emergency responders look for signage or labels on vehicles in order to deal with an emergency correctly and safely. Incorrect or missing signage can make decisions dangerous. Without the right information, more damage than good can happen. There is also the problem of too much signage, leading to confusion. That is why it is so important to be up to date on the regulations regarding the size of the vehicle as well as the amount being transported.
While the 100mm warning diamond labels are specifically for labels on the packaging itself, there is no objection to displaying them on the vehicle. Some may say that they have no relevance on a vehicle but emergency responders might disagree. As long as these labels can be removed from the outside of the vehicle once the hazardous material is removed, they can only help in identifying how to approach a vehicle in case of an accident.
Some may argue that, since most fire crews have access to a chemical database, they only need to know the UN Number of the substance on board and that they can get that from the operator. But if the driver has been incapacitated in the accident, that information would be lost to the rescue crew. A removable warning sign for transporting hazardous goods in a small van or trailer is still the best option. It is better to stay on the side of caution when lives could be at stake.