Under ADR a hazard warning placard must be 250 x 250mm in size. The surrounding black border must be 5mm in width and spaced 3-5mm from the placard edge.
Similarly, where a substance is packaged in a quantity greater than its limited quantity a 100 x 100mm UN warning label is required. A label must have a border of thickness no less than 2mm spaced 5mm from the diamond edge.
If signage is of an insufficient standard at the time of an accident consequences could be catastrophic and in some cases life changing.
