Prohibition sign (red circle and slash)

How to read it

ISO 3864-1, the international standard for designing safety signs, defines a prohibition sign as one that indicates “a specific behaviour is forbidden”. It has a white background, a red circular band and diagonal bar, and a black symbol, and the centre line of the bar passes through the centre of the sign and covers the symbol. ISO 7010 numbers these signs with a P: P001 is the general prohibition sign and P002 is No smoking. Great Britain’s Safety Signs and Signals Regulations 1996 set the same design, with the red part taking up at least 35% of the sign.

Also searched as: iso 7010 prohibition, no symbol, prohibition signs.

Prohibition signs in the British regulations

The 1996 regulations list eight: No smoking; Smoking and naked flames forbidden; No access for pedestrians; Do not extinguish with water; Not drinkable; No access for unauthorised persons; No access for industrial vehicles; and Do not touch.

Prohibitions with no sign of their own

ISO 7010 says the bar must not obscure significant details of the symbol. Where no registered sign exists for a prohibition, the standard provides for a new sign designed to the ISO 3864 principles, or the general prohibition sign P001 with supplementary safety information.

Look-alikes

US road signs use a red circle and slash for a prohibitory message too, on signs such as No Left Turn and No Parking. In the ISO system a solid blue circle is the opposite, a mandatory sign, and a red square with a white pictogram marks fire equipment.