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How do interchanges work when driving and what are traffic interchanges?

Find out more below...

Dan and Bex are on a road trip. They’re thinking about all the different types of interchanges – what DO they change into? The guys find out more…

Interchanges come in lots of shapes and sizes. When you leave a motorway, you might have noticed that you often drive up or down a ramp to join the next road on your journey.

Sometimes there might be a swooping loop or a roundabout to connect things together. These are all different types of interchanges.

The guys might not know it but they’re driving on a diamond! 

A diamond interchange that is!

Diamonds, Dumbells, Lilos and Cloverleafs are not things you’d expect to find on a road. And neither are Forks, Triangles and Trumpets but you’d be wrong.

They’re all different types of interchanges – and the names describe the way they look. Diamond interchanges are simple – straight and slanting roads rising up over the carriageways.

The very first interchange in Britain was a diamond interchange on the A1 at Welwyn. Diamonds are more frequently found on smaller roads because they need traffic lights where the roads cross, and that can slow things down.

Cloverleafs are more complicated, using four symmetrical loops to join roads together.

Smooth curves and roundabouts are great at keeping large volumes of traffic moving – but they’re more expensive to build and are difficult to change. And with growing numbers of vehicles on our roads, that’s a concern for planners.

One very famous interchange which connects a lot of roads is at Gravelly Hill in Birmingham.  It’s more commonly known as Spaghetti Junction and connects 18 routes in a combination which looks rather like a plate of spaghetti! 

At 80 foot high, it has 5 levels and over five hundred concrete columns. The design had to work around two railway lines, three canals and two rivers – quite a challenge!.

Over 200,000 vehicles travel over it every day. It has its own weather station, 46 traffic signals, three electronic signs and 25 roadside telephones.

Interchanges are designed to cope in the best way with the type of traffic that is using them and the conditions around those roads. Curves and roundabouts help to slow things down, which might be important where vehicles are coming into areas with people, housing, hospitals and schools.

Whereas straight lines might be better where the vehicles will be joining fast moving traffic.

MOBILE: Kids Guide to Transport: Rail and Road

Bex and Dan learn all about the future of Britain's roads and railways!

Are We There Yet? with support from the Royal Academy of Engineering

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Road to 2050

Find out more about why roads are built and how they help us get around the country.

More From Road to 2050