Signs
Circles give orders
Triangles warn
Rectangles inform
Blue signs generally give mandatory instructions, such as 'turn left' or indicate a route available only to particular classes of traffic, e.g. buses/cycles only
Red rings or circles tell you what you must not do, e.g. you must not exceed 30 mph, no vehicles over the height shown may proceed
Blue rectangles are information signs except on motorways, where blue is used for direction signs
Green rectangles are direction signs on primary routes
White rectangles are direction signs on non-primary routes, or for plates used in combination with warning and regulatory signs
There are a few exceptions to the shape and color rules
To give certain signs greater prominence - examples are the 'STOPvi
Warning Signs
Warning signs other than those for low bridges, railway and tramway level crossings, bus and pedal cycle facilities, traffic calming and road works.
Distance to STOP line
Distance to GIVE WAY line
Traffic signals ahead
Traffic signals that operate only at certain time
Junctions
Crossroads
T-junction
Side road
Priority through the junction is indicated by the broader line
Traffic merges from the left
Traffic merges onto main carriageway
Roundabout