The meaning behind yellow shapes on motorway and A road signs

WE have all seen signposts with yellow symbols on, but are none the wiser as to what they indicate.

Whether it be a square, circle, triangle or diamond – we often overlook them, having no idea what they are trying to make us aware of.

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What do the symbols mean?

An urban legend suggests the shapes are secret symbols to guide the great and good to the nearest bunker in a nuclear attack.

But there is actually a much less sinister explanation behind the mysterious markers.

The symbols direct traffic on to emergency diversion routes in the event of a road closure.

There are eight variations of the symbol for up to eight different exits or alternative routes.

How do they work?

Some motorway and A road signs will permanently display a designated symbol for each or some of the exits.

Other signs have a trigger that unfolds a panel showing a symbol when there is a road closure.

Temporary yellow-coloured diversion signs are then put up by the police or highway authorities that match these symbols depending on the route chosen.

These can be detailed, such as “M1 North closed. Follow [symbol] for alternative route” or can simply be a patch displaying the shape with an arrow.

They are designed so that drivers can easily recognise the symbol dotted across their new path, confirming they are on the correct track.

However, some diversion signs simply have an arrow on them pointing to the alternate exit.

Other yellow-coloured signs may just include the town or city name near the correct exit.

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What other signs are used on motorways?

Motorway road signs are easily distinguishable from others as they have a blue background.

Borders, writing and diagrams on the signs will always be in white writing to make them high contrast and easy to see.

As you are about to enter a motorway, you will see a sign depicting two lanes going under a bridge.

This is to let you know that you are about to join a motorway, an identical sign will also show you that you are leaving the highway.

Rectangular signs will show destinations, taking this shape as they are providing information.

There are often on the side of the road or overhead gantries.

Motorway junction signs will often have a black rectangle with white writing to tell drivers what junction this is.

This is particularly useful when using sat-nav directions which often tell you what number junction to leave the highway.

Countdown markers are commonplace whether you are entering or leaving the motorway with white stripes on a blue background.

Starting with three and working down to one, they indicate the number of yards from 300 down to 100.

This allows drivers to prepare to enter or leave the road.

Should you ever need to make an unexpected stop on a motorway or A road, you are likely to see a blue sign with white border and yellow writing on them.

Usually with three lines of text, these driver location signs, help breakdown and emergency vehicles locate you and are positioned every 500 yards or so.

The first number refers to the road you on, the second line notifies which way you are travelling, while the third line indicates how far you are from a given location.

Quite often you will also see brown signs, pointing to places of public interest or tourist spots.

In addition to permanent signs, you may also see traffic management signs which will give you advanced warning of lane closures.

These tend to be located overhead on gantries and allow active traffic management.