Recently, we reported on the secret – and not so secret – car features you never knew existed. Now, we’re donning our anoraks to uncover some hidden secrets of everyday motoring. Some you’ll know, but others might be news to you.

ARV symbol on police cars

See that symbol on the back of the BMW X5 police car? It means that it’s an Armed Response Vehicle (ARV), and the car is crewed by firearms officers. Such vehicles will also feature roof markings to make them identifiable to helicopters.

Double-length white lines

A broken white line will mark the middle of most roads. When the centre lines lengthen and the gaps shorten, it means there’s a hazard ahead. Do not cross it unless you can see the road is clear.

‘Wiggly’ road signs

The double bend sign actually shows you the direction of the first corner. In the case of the example shown, the road bends to the right, before turning left. If the sign is reversed, the opposite is true. The same rule applies to the standard bend sign.

Lampposts for unfamiliar bends

If you’re driving on an unfamiliar road, use lampposts to guide you through bends. Whether they’re on or off, the posts act like safe waymarkers.

Emergency diversion route symbols

Note the little black on orange symbols on the left of this motorway gantry. There are four shapes – square, triangle, circle and diamond – but they can be shown filled in or as outlined (as shown here). They’re for Emergency Diversion Routes, and can be used in the event of a motorway closure to guide motorists to the next junction. The drivers will be told to follow the symbol, with the route marked by the symbols and/or trigger signs.

Driver location signs

Look closely at this image and you’ll spot a blue sign on the verge. Driver location signs – or distance marker posts – were introduced in the early 2000s to alert drivers to the whereabouts of the nearest emergency phone. The top line shows the road you’re travelling on, the letter shows the direction of travel (usually A or B), and the bottom shows how far you are from a given location. The signs are positioned every 500 metres on a motorway, and can be used to guide the emergency services or recovery vehicle to a stricken motorist.

Airport signs

Once you’ve seen this one, you’ll never look at road signs the same way again. Thanks to our friends at PetrolBlog, we discovered that the little plane on a road sign faces the direction of travel to the airport. Not just the route, but the DIRECTION.

Coloured studs

Although we commonly associate reflective road studs – or cat’s eyes – with white ‘lights’ to mark the centre of the road, other colours are used for different uses. Red marks the left edge of the road, amber marks the central reservation of a dual carriageway or motorway, green marks the edge of a layby or slip road, while green/yellow studs are used for temporary adjustments to lane layouts.

Route numbers in brackets

If a road number is shown in brackets, it means that the road in question can be reached by taking the route indicated. Helpful if you’re driving in a city and are searching for the nearest motorway.

The distance to London

Have you ever wondered where the distance to and from London is measured? No? We’re going to tell you anyway. It’s Charing Cross, and it dates back to 1290 when a memorial cross (one of 12) was installed south of Trafalgar Square.

Pavement ‘art’

No, you haven’t discovered a Banksy or ancient hieroglyphics. The dots and arrows painted on our pavements are used by utility companies to signify what lies beneath the ground. We’d urge you to visit the BBC website for more details on the ‘squiggles’. You’ll lose at least half your lunch hour…

Head up, foot up

This one dates back to a Suzuki launch in North Wales. On it, we were given a set of instructions to follow a set route and told to watch out for sheep, but to take extra care when the woolly ones weren’t grazing. ‘Head up, foot up’ – basically, slow down if the sheep isn’t eating. ‘Head down, foot down’ – if the sheep is eating, you’re fine. We say: always slow down for sheep.

Yellow ‘H’ signs

The little yellow signs are a common piece of street furniture, but have you ever stopped to wonder what they mean? They’re used to show the location and size of the nearest hydrant. In the case of the example shown, the size of the water main is 75mm, and the distance is 10 metres.

Escape lanes

Escape lanes are sand traps located alongside the downhill side of a steep road which are designed to ‘catch’ a vehicle in the event of brake failure. As braking technology improves, they’re becoming less common, but you’ll often see evidence of a driver forced into making an impromptu visit to the ‘kitty litter’.

Dartmoor road signs

There are three different direction signs on roads in and around Dartmoor. Signs with a blue border show roads that are generally suitable for all traffic, while signs with a brown border are used for roads which are smaller with passing spaces. Finally, signs with a black border are unsuitable for large vehicles. The brown signs are not to be confused with the common tourist signs, which can be seen across the country.

‘Mystery’ junction

Anyone who has travelled eastbound along the M4 has probably spotted the exit marked with ‘Works unit only’ signs. Conspiracy theories exist, but it’s actually used for RAC Welford, which is one of the largest European ammunition compounds for the United States Air Force. According to Forces Reunited, it’s at its busiest when the U.S. government deploys bombers to a forward air station at RAF Fairford.

Baby on board sticker

Baby on board stickers were designed to encourage other drivers to be more considerate and to alert the emergency services that a child or baby is on board in the event of an accident. This isn’t so much a ‘hidden secret’, more a case of the sticker losing its meaning and impact. A ‘Westlife fan on board’ sticker wouldn’t encourage many of us to drive carefully.

Roadside milestones

According to the Milestones Society, mileposts became compulsory on all turnpikes in 1767. Their role was to inform travellers of direction and distances, as well as keeping coaches on schedule. Around 9,000 survive today, as many were removed or defaced in World War II to baffle German invaders.

Old toll houses

Toll houses were built at turnpike gates to collect tolls from road users. Today, their unique design makes them easy to spot, you just haven’t noticed them yet. They’re especially prominent in the West Country.

Hidden secrets of everyday motoring