WPQ answer – Air quality speed limits

The Department for Transport has provided the following answer to your written parliamentary question (15521):

To ask the Secretary of State for Transport, what criteria are used to determine when temporary air quality speed limits are used on the M4 near Heathrow. (15521)

Tabled on: 26 February 2024

Guy Opperman:

National Highways implemented a speed restriction of 60mph on the M4 westbound at junctions 3 to 4 in December 2022 to achieve nitrogen dioxide (NO2) compliance in the shortest possible time.

The answer was submitted on 04 Mar 2024 at 14:32.


  1. Peter Wood
    March 7, 2024

    Good Morning,
    Does the transport department actually measure NO2 levels in the adjacent populated areas to the junctions of the M4 mentioned? If so what are they compared to background levels?

    1. Lifelogic
      March 7, 2024

      Indeed a car at 70 might emit very slightly more than one doing 60 I suppose on average? But it is surely all about cash cow cameras & pollution is just a ruse.

      Plus cars going at 70 will cause any pollution to disperse rather more rapidly as the cars cause more turbulence with their higher speeds..

      1. Peter
        March 7, 2024


        I had been expecting one of your ” ….is surely correct in today’s Telegraph” posts. Alister Heath? Serfdom?

        You are lucky DOM doesn’t do Telegraph posts, or you would have been eclipsed by his very particular choice of adjectives to describe a rather gloomy future.

  2. Sakara Gold
    March 7, 2024

    Once again, the Chancellor failed to mention either exports, nor manufacturing or the national debt. On the face of it, nothing in this budget to reduce the total government tax take – which is now at 37.5% of GDP

    The gold price has broken past it’s previous record high in 2018 and last night was trading at $2154.10/oz (£1692.00/oz) . The factors that supported central banks’ near-record gold purchases in 2023 continued into the new year and if January is any indication, 2024 will be another blowout year for the yellow metal.

    Physical demand for gold bars and coins has also absorbed what gold was available on the London Bullion Market and a strong Lunar New Year saw Chinese consumers buying gold as a hedge against the country’s beleaguered stock markets and real estate sector.

    China, India and Iran central banks remain major purchasers of the gold. Unfortunately for the British taxpayer, the BoE has now sold all our gold – at prices far below the current spot price. Chancellor Hunt, again, made no mention of investing sterling into the ultimate hedge against inflation and so we shall miss out on the current precious metals rally.

    1. Sharon
      March 7, 2024

      @ Sakara

      This seems more proof that Britain is being deliberately run down!

  3. Ian wragg
    March 7, 2024

    Looking at the budget 3 things stand out.
    1 vat on energy has not been abolished.
    2 public chargers are still taxed at 20%.
    3 the so called tourist tax hasn’t been abolished
    All 3 have the common theme that even if the Chancellor wanted to abolish them it wouldn’t apply to Northern Ireland highlighting that VAT is a Brussels competence even after we are supposed to have left.

    1. Diane
      March 7, 2024

      JH has admitted privately to colleagues apparently ( Guardian report ) he can’t raise the VAT threshold (by more than the £5000 stated in the budget ) for UK businesses due to EU rules. VAT policy still c/o our friends in Brussels. From that, one assumes that is also why VAT overall is being left well alone in other areas incl. perhaps VAT on our energy ? Further, I noticed a figure mentioned last month in the DT (03/2/34) of £590 million paid out in 2023 on wind farm constraint payments which no doubt added to our energy bills too. The question of the Tourist VAT issue demonstrates a lack of vision IMO & seeing the wider picture in terms of additional potential spend.
      Air quality – then we need to know exactly what are the results of the actions taken.

      1. Mark
        March 8, 2024

        We are into the phase where wind constraint payments will be increasing quadratically with increases in capacity. This is because there will be more hours with surplus wind because of the extra capacity, meanwhile for the low demand hours where wind surpluses already occur, the surplus to be curtailed simply gets bigger.

        Eventually we would reach a point at which all the windy hours produce a surplus, which therefore simply grows if more capacity is added, while the windless hours still leave us desperately short of electricity.

        The alternative to constraint payments is subsidies for exports of surplus electricity. There are already some hours where the export price is negative: GB consumers get to subsidise Continental consumers by paying for ROCs and CFD compensation paid in respect of the generation. To be able to export more there has to be a big investment in extra transmission capacity by National Grid (currently the subject of a radio advertising campaign), and more interconnectors better suited to export. The cost of that too will go on our bills.

    2. Ian wragg
      March 7, 2024

      I’ve just been checking electricity flows for the past year and we’ve barely exported 5% of the amount imported. Is this the governments idea of being the Saudi Arabia of wind with net imports running annually at around 18%.

    3. glen cullen
      March 7, 2024

      Excellent point

  4. Sakara Gold
    March 7, 2024

    Last year Sunak, heavily influenced by Big Oil and the fossil fuel lobby, changed the timetable for the introduction of EV’s to the British market. As a result, Nissan have stopped production of their Leaf EV in Sunderland, BMW have moved production of their electric Mini to Germany, Honda have shut their Swindon plant and Aston Martin have given up on EV’s altogether. This stupid decision, which was not requested by the SMMT, has cost us thousands of well paid manufacturing jobs.

    Reply Complete nonsense. Those decisions had nothing to do with Sunak’s realistic decision.

    1. Original Richard
      March 7, 2024

      SG :

      The transition from from ices to bevs will decimate the West’s car manufacturing businesses and swamp our market with subsidised Chinese bevs manufactured using coal-fired energy.

      Sunak changed the timetable for the eventual banning of the sales of new ices to match the EU but has not changed at all the timetable, the quotas and the £15K/vehicle fines on Western car manufacturers who do not sell an increasing quota of bevs each year up to 80% by 2030.

      It is clear that the reason for the unilateral Net Zero Strategy is to destroy Western jobs and become more dependent upon China.

      The SMMT is simply another communist captured organisation.

    2. Roy Grainger
      March 7, 2024

      You plainly have no clue what the schedule for the switch to EVs in Germany is do you ? Why don’t you do some basic research before posting your conspiracy theories ?

    3. Lifelogic
      March 7, 2024

      Drivel, Sunak’s tiny touch on the brakes was absolutely pathetic anyway, we need an emergency stop and a handbrake U turn. Ditch the net zero religion in full & now It costs £ trillions deliver net harm and achieves absolutely nothing. EV cars do not even save CO2 not that CO2 is even a problem.

      Odd that this government and the BBC accepts the climate alarmist/climate emergency bogus settled “science” drivel yet not (it seems) the far clearer & very different genetic structures, in each and every cell, of male and females.

    4. Richard II
      March 7, 2024

      SG: Honda shut their Swindon plant in 2021, 3 years ago and two years before Sunak had the good sense to apply the brake (a bit) to EVs and Net Zero. I’ve seen more authentic text than yours from an AI device.

  5. Ian wragg
    March 7, 2024

    When is the government going to publish the next stage of its net zero plan you know the one where all regional airports are closed and non compliant (95%) of ships won’t be allowed in uk waters.

    1. Sharon
      March 7, 2024


      And we’re to use dried mud to patch up repairs on our houses? And for new builds, as cement is being phased out?

      1. Mickey Taking
        March 7, 2024

        that is what was used for Devon Cob and Lime.

    2. Original Richard
      March 7, 2024

      Yes, the UN/WEF/the Government/the CCC/the BBC et al are not being honest and straightforward by not informing us that the ultimate aim of our unilateral Net Zero Strategy is to reduce our living standards to those similar to such authoritarian states as the Democratic Republic of Korea using the conspiracy theory that the West’s burning of hydrocarbon fuels will destroy the planet.

      If we were still a democracy then the implementation of such massive life changing policies, such as the unilateral Net Zero, which will bring us ruinously expensive, chaotically intermittent energy and government control through electrification and smart meters, would only be mandated via a referendum.

      1. Mitchel
        March 8, 2024

        Democratic People’s Republic of Korea,if you don’t mind!

  6. Lynn Atkinson
    March 7, 2024

    So no answer.

    1. Lifelogic
      March 7, 2024

      It is nothing to do with pollution & all about cash cow tax raising cameras. A hugely inefficient and damaging way to raise tax.

      So the budget is not popular with anyone at all take 2x with one hand and give X back with the other. Well done Hunt. He says he would like to reduce taxes but cannot due to Covid and the energy crisis caused by Putin’s war.
      But no this a untrue it is due the appalling way Covid was dealt with lockdowns, covid loans, endless corruption and net harm vaccines and net zero is the cause of rip off energy prices.

      Other endless government waste like HS2, pointless degrees, net zero and open door immigration, bloated inept government… are the reasons the government feels the need to rob the people even more.

      We need a government that will reduce the size of the state, ditch net zero, reduce taxes, cut immigration hugely and deregulate. Both Labour and the Con-socialists are wrong on all these issues. Labour even worse than the this dire government.

    2. Berkshire Alan
      March 7, 2024

      Lynn, did you expect one.
      Nothing to do with the wind speed, weather, cloud cover, humidity, temperature, etc etc.
      Thus they simply say it is down to speed, given that at 60 mph most cars will be in top gear, at 70 mph the situation will be the same, so the engine revolutions “per mile” will be exactly the same (as they are in the same gear) !
      Yes you will lose a little more fuel at the higher speed as the wind resistance of the vehicle will be greater at a greater speed, but that difference is small at those speed differentials.
      My car revs at just over 2,000 revs per minute at 70mph in 8th gear (top gear)
      It also revs at just under 2,000 revs per minute at 20mph when in 3rd gear, thus I produce more pollution “per mile” in 3rd gear, than I do when in 8th gear or top. That is why 20mph speed limits simply for for air pollution reasons are an absolute nonsense.
      The fact is we have idiots in charge, who do not think things through with the proper and factual information based on science, physics, common-sense, and human nature.

      1. Mickey Taking
        March 7, 2024

        something awry here Alan. Given a car is in a specific given gear – the revs to do 70 mph have to be higher than doing 60mph. Either that or ICE cars have cheated physics.

        1. Berkshire Alan
          March 7, 2024

          You made the mistake of not reading clearly what I said, I said REVS PER MILE would be the same, IF IN THE SAME GEAR, the gearing is fixed in 8th or top gear, as is the distance measured over a mile, the wheel revolutions are also the same, over the same comparative distance..
          Only when you CHANGE GEAR to a lower gear is there a variance, hence you then get less distance per engine revolutions, when in a lower gear like 3rd.
          Thus if you use more revs PER MILE as you will in a lower gear, you get less miles to the gallon and more pollution per mile.

      2. Mark
        March 8, 2024

        Cars differ. In mine, I can cruise at 70mph in 6th, but at 60mph I will need to drop to 5th if not more or less coasting (i.e. for any upward incline), or if I am forced to a lower speed by braking ahead of me. In terms of pollution, maintaining a steady speed results in the best fuel consumption. The mpg penalty for 70mph or even a Continental 80mph is quite small: the big fuel consumption penalties come at lower speeds, particularly in heavy traffic. The Welsh 20mph zones force the use of 2nd gear, even with no traffic.

      3. Mark
        March 8, 2024

        Cars differ. In mine, I can cruise at 70mph in 6th, but at 60mph I will need to drop to 5th if not more or less coasting (i.e. for any upward incline), or if I am forced to a lower speed by braking ahead of me. In terms of pollution, maintaining a steady speed results in the best fuel consumption. The mpg penalty for 70mph or even a Continental 130kph is quite small: the big fuel consumption penalties come at lower speeds, particularly in heavy traffic. The Welsh 20mph zones force the use of 2nd gear, even with no traffic. Using too high a gear at low speeds also causes an increase in fuel consumption, and eventually stalls the engine. Each gear has its sweet spot range of speeds and loads.

        1. Berkshire Alan
          March 9, 2024


          Exactly my point more fuel consumption and more pollution PER MILE the lower the gear you are using because your engine in revving at more REVS PER MINUTE for less distance.

    3. Bloke
      March 7, 2024

      Yes; NO answer Lynne.
      Guy Opperman’s reply is rather like those of basic computer programmes which pick what they regard as key words and form odd sentences including them.
      He didn’t recognise the word ‘quality’ in the question, so in compliance with idiocy his Computer said NO2 !

    4. Lifelogic
      March 7, 2024

      Indeed pathetic as usual.

      JAMES BARTHOLOMEW The NHS is our national shame. It’s time to abolish it
      Jeremy Hunt’s claim that the health service is “the biggest reason most of us are proud to be British” was scandalous.

      Total lunacy from Hunt try asking the 7.7 million on the waiting lists. It also shows Hunt is a totally out of touch socialist, net zero pushing damn fool. The NHS is clearly better than no healthcare at all but it is appallingly run. The Covid Vaccines they pushed (even into people with not need of them) clearly did net harm. This a fact they are currently trying to hide. They will fail in this. The statistics are overwhelming and worldwide yet still being pushed.

      See the excellent Dr Clare Craig Xs and the Dr John Campbell videos.

      1. Lifelogic
        March 7, 2024

        Jeremy Hunt’s non-dom tax is economic madness
        The abolition and replacement of non-dom status is a worthless offer in terms of inducing such people to settle and run businesses

        Correct as usual it will raise a negative net sum and damage the economy and jobs even further. Will be good for other Tax havens and Ireland’s Non Dom regime with CR at half UK rates too. More insanity from Socialist and economic illiterate Hunt and Sunak both PPE Oxon I understand. The best and obvious way to boost taxes, living standards and the economy is to scrap all the May & Ed Miliband net zero insanity mate! This costs nothing as would a bonfire of red tape. But no the Tory and Labour loons cannot see this.

      2. Mickey Taking
        March 7, 2024

        Millionaires always seem to praise the third rate services, because they don’t need to pay for them in the way the plebs do, nor have to wait years to use them.

    5. Lynn Atkinson
      March 7, 2024

      And this is my MP. Can anybody advise me, with a straight face, to go and vote for this man?
      I can, however, assure you Sir John, is that his answer was fulsome compared with those I receive – or rather don’t receive – from the Conservative Party Chairman.
      I have a long-standing problem at a commercial property in Consett. I actually got the Council to issue proceedings – then they faded into the wild blue yonder. The MP – the Party Chairman whose own Agent resigned, refuses to respond at all. My tenant has banned him from the premises.
      I am going to the national Press closer to the election.

  7. Mickey Taking
    March 7, 2024

    What was the reading (of nitrogen dioxide) along certain points of the M4 where it (unannounced) was reduced to 60mph? Sometimes the area is fairly busy and other times lanes are empty! I assume it has reduced else why do it?
    It strikes me as a random decision by some green supporting fool.

    1. Know-Dice
      March 7, 2024

      And it’s only 1 hotel nearby, virtually no nearby residential properties. Just virtue signaling for no reason

    2. Berkshire Alan
      March 7, 2024

      Interesting that it only applied one way, on one side of the road, just to make the answer even more ridiculous.

      Clearly the logic therefore, is that the central barrier is working as an air filter. !!!!!!

      1. Mickey Taking
        March 7, 2024

        or Know-dice is on to something – what is coming out or being absorbed at that Hotel!

    3. Mark
      March 8, 2024

      Here’s the NAEI map for NO2 emissions by 1km grid square for all sources for a swathe centred around Heathrow: point sources such as sewage farms, hospitals, a few factories etc. are highlighted with a marker. It’s clear that the major source is aircraft arrivals and departures, with the individual runway approach paths standing out. There appears to be nothing in particular to mark out the M4 near Heathrow as being different from other sections of the M4 or M40. However, the M25, where even lower limits are quite frequent (often regardless of traffic levels) on the section between the A3 and the M40, does get some red boxes, but many of these are associated with nearby point sources. However, it is enough to suggest that causing traffic jams by slowing the traffic to a crawl is not helpful.


      Here’s the picture for NO2 emissions from major road traffic, which confirms the impression given by the total


      Other important sources of emissions are non industrial combustion plant (central heating, log burners etc.), and the main railway lines – which may be surprising given the amount of electrification. The map can be found here for those who wish to explore in more depth:


      Over time it is clear that weather conditions are the main factor in making pollution worse than normal: imported pollution from the Continent when the wind is in the wrong direction, and held close to the ground when there are inversion layers and minimal zephyrs to clear it away. The aftermath of major fireworks is also liable to create significant pollution.

  8. Mike Wilson
    March 7, 2024

    My Mum and Dad are very close to the M4, between J3 and J4. Very near J4. They don’t give a monkey’s about Nitrogen Dioxide levels. Mind you, they are in Cherry Lane Cemetery.
    If the 3rd Heathrow runway is ever built, they will be dug up and moved. Which I have to say is a rather upsetting thought.

    1. Mickey Taking
      March 7, 2024

      Commercial Aircraft will be banned before long, smaller airports will thrive on the privateers!
      I doubt a case for another runway will be acceptable.
      You and they can rest easy.

    2. Bloke
      March 7, 2024

      ‘Cherry Lane’ envisions a place of calm and rest blossoming in gentle English countryside.
      The notion of even more noisy aircraft shattering the peace destroys the rest in the environment, affecting everyone near.

  9. Roy Grainger
    March 7, 2024

    You might also ask if they imposed temporary speed limits on all the planes landing and taking off nearby at Heathrow which emit much higher NOX levels per passenger than cars.

    1. Mickey Taking
      March 7, 2024

      Great idea – we should insist the planes cannot exceed 60 mph on take-off or landing.

  10. William Long
    March 7, 2024

    The need to ask these questions, and the replies to them, are stark illustrations of how OUR money is being wasted by Civil Servants at this Government’s behest. We deserve much better.

  11. glen cullen
    March 7, 2024

    You asked ‘what’ and they answered ‘when’

  12. Original Richard
    March 7, 2024

    What is the figure please for the % reduction in NO2 levels when the speed limit is rduced from 70mph to 60mph?

    Cars may emit less/minute but will be travelling for longer in the area.

  13. Original Richard
    March 7, 2024

    I would like to see please the figures for the annual spend on Net Zero subsidies and grants etc. (I don’t know all the titles of all the spending plans) and how much is collected in carbon taxes.

  14. Sharon
    March 7, 2024

    Re the budget / off topic, sorry. Ewan Stewart, City economist , writes in TCW and sums up where we are.

    “The problem has been at least 25 years in the making, exacerbated for sure by very poor policy choices over the last five years. Simply put, the UK has moved from a broadly free market economy 25 years ago to a highly managed state- and regulation-driven one today.

    In 1997 the state accounted for about one third of the economy. Today it’s almost half. This in itself underestimates the problem as regulation particularly in financial services, energy, employment law and the like has increased exponentially, further undermining market responses. The UK is a post-free market economy. It is now statist, centralised and controlled, and with it opportunity has withered.

    As a result of this shift, which is not addressed at all by yesterday’s Budget, the UK has become an ex-growth economy and one driven more by keeping close to the regulator or government, rather than by free enterprise.”

    Deeply depressing.

  15. Kenneth
    March 7, 2024

    Since the Secretary of State for Transport did not answer the question, is there a way to force the government to answer the question?

    I know the BBC would not pursue this as it would not fit its political views to do so but I would hope other media outlets could do so?

    1. BOF
      March 8, 2024

      All our MSM have millions in funding from the BMGF. You will be hard pressed to find one to pursue the matter.

  16. Bert+Young
    March 7, 2024

    The budget has done nothing for me to change my views on the ineffectiveness of the Sunak/Hunt regime . The “Hoo – Hah ” in the Commons was a load of tripe and I witnessed nothing to convince me that the Conservatives could change public opinion . Labour has been handed a bonus to kick start their campaign . The record of the OBR is shameful and it must not continue its influence .

  17. George
    March 7, 2024

    Hi sir John
    There are speed restrictions on the M6 going through Birmingham set at sixty traffic is always very busy so slowing traffic down causes bunching up and more pollution the speed due to bunching up drops down to 30 40, miles per hour the M42 is the same they display speed levels as low as 30 mph causing massive tail backs and more pollution

    1. Mickey Taking
      March 7, 2024

      exactly – these daft theoretical ‘smart-limits’ actually cause unnecessary braking, accelerating, when the idiot designer wanted a smooth spaced flow! UNINTENDED CONSEQUENCES.

  18. Julian Flood
    March 7, 2024

    Petrol cars produce NOx. Cars running on methane (AKA natural gas) produce almost zero NOx and half (ish) the CO2. If only the UK had available plentiful and cheap supplies of natural gas (we have) we could solve two problems at a stroke. And if there’s any left over (there is) we could reduce costs for British industry.


  19. Original Richard
    March 7, 2024

    JF :

    You’re correct. But the purpose of electrification, which includes bevs, is to be able to provide population control down to the individual level via smart meters.

    Vehicles running on CNG will not provide this level of control.

  20. Mickey Taking
    March 8, 2024

    ‘to achieve nitrogen dioxide (NO2) compliance’.
    Compliance with what?

    1. Mark
      March 8, 2024

      Back in 2005, WHO set Guidelines NO2: 40 μg/m3 annual mean; 200 μg/m3 1-hour mean. These were unchanged from previous guidelines, and quite ambitious for some third world cities like Kathmandu, where levels of over 400 μg/m3 are common due to being in an enclosed mountain valley at altitude (where engines burn less efficiently).

      In 2021, with their new found self-importance following the covid pandemic, WHO produced new guidelines of 10 μg/m3 annual mean; 25 μg/m3 24-hour mean. Despite the earlier guidelines pointing out that studies found it very hard to separate the effects of one alleged pollutant from another, only noting observable effects in laboratory conditions at concentrations well above 500 μg/m3. Despite the plethora of studies since, they all suffer from the same problem of collinearity with other possible pollutants. Despite the enormous uncertainties WHO claim there would be a small decrease in respiratory mortality to justify the new standard – completely unmeasurable, especially in the light of covid mortality swamping the statistics.

      UK actual NO2 emissions history by setting is in this chart:


      In reality, it’s just another attempt to shut down Western economies using regulations. Meanwhile Kathmandu will continue to enjoy levels of 400 μg/m3 whatever WHO say.

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