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How do traffic lights work?

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Dan and Bex are on a road trip. They are waiting at some traffic lights and wondering how changing lights help traffic – and how traffic lights might change in the future. 

Even if you aren’t old enough to drive, chances are you know a lot about traffic lights. They’re signals you find on roads which help different road users to take turns, keeping things safe and smooth.

Red means stop, amber means get ready and green means – can you guess?

Green’s for go, of course!

Green and red are also used at pedestrian crossings too, where you wait for the Green man before you cross.

Signals using lights have been around a long time. Gas powered lights were introduced in London in the 1860s to manage horse riders and carriages on the bustling Victorian streets.

Traffic was controlled by a police officer using arm signals during the day and by lights at night. Unfortunately, they had a tendency to explode…

But things got better. Electric traffic lights were introduced around the turn of the 20th century. They were needed more than ever as the amount of cars on the roads began to increase…

Today, the most basic type of traffic lights run on a timer, giving say a minute for each direction.

Trouble is, this doesn’t always take into account who or how many are using the junction. Pressure plates, cameras, radar and induction loops can monitor the number of vehicles approaching a junction and change the timing of lights accordingly, giving more green light to the busier route.

And if there’s an emergency, this information can be digitally shared to change the timing of lights to aid the emergency services.

The future’s certainly bright! Some traffic lights already use GPS to give priority to buses – especially when they’re running late – and as technology improves connected vehicles will communicate with each other and with the traffic signals in even more clever ways

Vehicles will be told where the next set of traffic lights are and when they’re due to change colour.

Cars can then automatically slow down so that they arrive at the lights just as they change to green. No need for any idling – which is good for the environment, keeping the air cleaner.

In time, signals may even “ask” the cars where they are going and change traffic signals accordingly.

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