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Motorway speed limits cut to curb pollution

Could a simple measure such as a speed limit cut be enough to reduce emissions on some of the UK's busiest roads?

Heavy traffic on the motorway

In 2021, the transport sector accounted for 31.5% of the UK’s total carbon emissions, according to the government

The UK has set itself an ambitious target to become a zero-carbon country by 2050, but we won’t reach that target unless the government takes greater action.

To that end, Highways England has cut the speed limit on certain sections of motorway to 60 mph. Wales has also expanded its network of 50 mph zones.


What are the speed limit changes on motorways in the UK?

There have been changes to 8 stretches of motorway in England, these are in:

  • Salford
  • Leeds
  • Birmingham
  • Bristol
  • Sheffield 
  • Gateshead 
  • Smethwick
  • Hanwell

The speed on these stretches of motorway has been reduced from 70 mph to 60 mph in a bid to reduce emissions.

In Wales, 5 stretches of motorway had their speed limit cut to 50 mph between 2018 and early 2021. 

How does speed impact carbon emissions?

Speeding up requires power, which burns more fuel. Slowing down uses the brakes, which give off harmful brake-dust particles.

With constant speeding up and slowing down on the motorway, you can see how pollution can build up fast.

Cutting the speed limit to 60 mph rather than 70 mph means less acceleration. This means less fuel consumption and fewer emissions.

Highways England estimates that a 60 mph speed limit on the motorway could cut emissions by as much as 17%.


Where are the 50 mph zones in Wales?

In early 2021, a new average 50 mph zone was introduced on the M4 between junction 24, Coldra, and junction 28, Tredegar Park.

But this wasn't a new initiative for Wales. In 2018, five stretches of road had their speed limits cut to 50 mph because of emissions:

  • A494 at Deeside
  • A483 near Wrexham
  • M4 between junctions 41 and 42, Port Talbot
  • M4 between junctions 25 and 26, Newport
  • A470 between Upper Boat and Pontypridd

Emissions in those areas fell enough that the new speed limits became permanent in 2019.


Are these 50 mph zones the same as a temporary minimum speed of 50 mph? 

The new 50 mph zones in Wales are replacing the temporary minimum speed of 50 mph. 

Prior to this there was a variable speed limit system between J24 Coldra and J28 Tredegar park of the M4. 

The variable speed limit could change depending on traffic conditions. For example, the variable speed limit could be set at 40 mph if there’s high traffic. But now this should remain at 50 mph to help reduce pollution.



Where are the revised speed limits in England?

They're on four stretches of motorway around Birmingham, Manchester and Sheffield:

  • M6 junctions 6 to 7, Witton
  • M1 junctions 34 to 33, Rotherham
  • M602 junctions 1 to 3, Eccles
  • M5 junctions 1 and 2, Oldbury

Highways England has identified another 4 areas with poor air quality, but these roads already have speed restrictions in place for other reasons:

  • M4 junctions 2 to 4, due to roadworks
  • A1 Blaydon Gateshead, due to roadworks
  • M621 junctions 6 to 7, Leeds, original permanent speed limit is 50mph
  • M32 junctions 1 to 3, due to roadworks

The lower speed limits will be in force 24 hours a day during the trial.


Are electric cars exempt from revised speed limits?

No, the speed limit applies to all vehicles.

Even though electric cars have zero emissions, they still need to stick to the new speed limit for safety and practical reasons. Having one rule for EVs and another for everyone else could cause confusion.

Ivan Le Fevre, head of environment at Highways England, said:

“Ultimately the air quality challenge will be solved ‘at the tailpipe’ by vehicle manufacturers and changes in vehicle use.

“Until this happens, we will continue our extensive programme of pioneering research and solutions.” 


How can I reduce emissions when I drive?

Reducing your speed is one way to keep your emissions down.

But if you want to do more, here are some tips:

  • Inflate your tyres to the correct pressure
  • Remove excess weight in the car
  • Switch off your engine when you’re stuck in traffic
  • Maintain a steady speed to avoid unnecessary acceleration or braking
  • Service your car regularly

You might think these tips sound an awful lot like how to improve your fuel economy. That’s because they are!

If you improve your fuel economy, your car burns less fuel. Fewer emissions are pumped into the air, and you save yourself some cash by not topping up as often. And with the rising cost of petrol prices, this can only be a good thing.

This defensive style of driving is also safer, leading to a lower risk of making a claim in your car insurance policy.

You can find out how much your journeys are costing you with our fuel cost calculator.

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Speed limits

It’s important you know your speed limits. Breaking the speed limit is breaking the law, and as well as being dangerous you could be hit by a hefty fine, or be disqualified from driving.


What is the speed limit on a motorway? 

The speed limit on the motorway is usually 70 mph unless signs say otherwise. On some stretches of motorway the speed limit can vary.

These are sometimes used if there’s heavy traffic in a particular area, road works or to reduce emissions. Always keep an eye out for speed limit signs when you’re driving on a motorway.


What is the national speed limit?

National speed limits vary depending on what vehicle you’re in.

The government publishes a full list of all the limits, but for cars and motorbikes weighing up to 2 tonnes, the national limits are:

  • Restricted road: 30 mph.
  • Single carriageway: 60 mph.
  • Dual carriageway: 70 mph.
  • Motorway: 70 mph.

What is a fixed speed limit?

These are speed limits that are shown by a number inside a red circle on a road sign as you enter the speed limit zone. The limit remains in force until another sign tells you otherwise.


What are local speed limits?

Local authorities can set their own speed limits – many towns and cities have 20 mph zones, for example.

You should keep an eye on the signs at all times because the speed limits can change regularly over short distances – around schools, for example.


What is a variable speed limit?

Variable speed limits are becoming more common thanks to the increased rollout of smart motorways.

It means that the speed limit can be adjusted depending on factors such as traffic flow and congestion.

Never assume that just because you could do 70 mph yesterday, you can definitely do 70 mph again today.


Is there a minimum speed limit?

If you see a blue circular sign containing a number, that indicates there’s a minimum speed limit – you shouldn’t go any slower than that.

These are mainly used in places where it’s important that traffic keeps flowing, such as in tunnels.


What are restricted roads, motorways and dual carriageways?

These are roads in built-up areas, and it can sometimes be unclear what the speed limit is if you haven’t been paying attention to the road signs.

Usually, though, if you can't see any speed limit signs and there are buildings and street lights alongside the road, the speed limit is 30 mph.

If the limit is something different, such as 40 mph, you should expect to see regular reminders of that.