Triangular road signs are available in 450mm, 600mm and 750mm sizes.
Class RA1 Engineering Grade or RA2 High Intensity Prismatic reflectivity
Wall mounted or with rear channel for post fixing
DOT Transport Diagram 544
Official specification Sign Posts.
The Department for Transport encourages the use of either '20 mph speed limits' or '20 mph speed limit zones' in urban situations where vulnerable road users are at particular risk.
Traffic calming zones are located in areas with a high level of pedestrians such a town centres or schools. The end of the 20 mph speed limit traffic calming zone sees the limit increased to 30 mph.