Crazy proposal to raise speed limits above speed limiter settings

As a bizarre consequence of the failure to switch to metric speed limits, the Department for Transport (DfT) is proposing to raise the motorway speed limit of coaches and buses from 60 mph (96.6 km/h) to 65 mph (104.6 km/h). That’s 4.6 % faster than the 100 km/h maximum speed that their speed limiters allow.

Ironically, the proposal is one of a number of changes actually intended to align motorway speed limits with commercial vehicle speed limiter settings.

Speed limiters are required by law to be fitted to all new heavy goods vehicles (HGVs), and passenger carrying vehicles (PCVs). 90 km/h is the setting used for all HGVs over 3.5 t, and 100 km/h is the setting for all PCVs capable of carrying more than 8 passengers.

In recent years, as older vehicles have gradually been replaced by newer ones fitted with speed limiters, the de facto commercial vehicle motorway speed limit has become 90 km/h for HGVs, and 100 km/h for coaches and buses. As a consequence, it obviously makes sense to review commercial vehicle motorway speed limits and align them with corresponding speed limiter settings.


Yet, rather than opting for the obvious solution of setting commercial vehicle motorway speed limits equal to their corresponding speed limiter settings, the DfT has proposed rounding up to the nearest 5 mph. This means that all commercial vehicles will have motorway speed limits higher than their speed limiter settings. In their consultation document they state,

it would be unrealistic to align the relevant speed limits exactly with speed limiter settings”.

Presumably, the option of setting speed limits in km/h, the same units that define speed limiter settings, has been overlooked.

Whilst it would be undesirable to have a mix of mph and km/h speed limit signs on our roads, the fact that speed limits for commercial vehicles are not signed means that there is no good reason why motorway speed limits for HGVs and PCVs cannot be defined in km/h, as speed limiter settings already are.

Also, as speedometers are required to show speeds in km/h, as well as mph, drivers of vehicles not fitted with speed limiters should have no problem complying with speed limits in km/h. The ideal solution to the DfT’s conundrum is therefore perfectly practical – commercial vehicle motorway speed limits can be aligned exactly with speed limiter settings.

Of course, having speed limiter settings defined in km/h, as is required by international regulations, means that regardless of how the DfT eventually choose to define new HGV and PCV speed limits, the reality will remain that two different systems of speed measurement are being used on our roads – a situation that can only be satisfactorily resolved by switching to km/h speed limits for all vehicles.

We would therefore recommend that the DfT should as soon as possible initiate a comprehensive plan to complete the switchover to metric units for all road traffic purposes – something that was originally scheduled for 1973, but was postponed in 1970 without a new date being set.


The Department for Transport is inviting comment to their speed limit proposals in a public consultation.

The UK Metric Association’s consultation response can be viewed at the following link:

The consultation remains open until 27 April 2010.


Consultation on Heavy Goods Vehicle and Passenger Carrying Vehicle motorway speed limits.

Speed Limiter Legislation

The Road Vehicles (Construction and Use) (Amendment) (No.2) Regulations 2004
The Road Vehicles (Construction and Use) (Amendment) (No.5) Regulations 2005

House of Commons – Roads (Speed Limit Signs)
9 December 1970 vol 808 cc417-8

UKMA’s leaflet Traffic Signs 2.0, summarising the case for metric signs, can be downloaded by clicking on this link.  Alternatively, free printed copies can be obtained by e-mailing

19 thoughts on “Crazy proposal to raise speed limits above speed limiter settings”

  1. If this article had been published yesterday, I would have assumed it was an April Fool – but, incredibly, it does seem to be true. The absurd lengths to which the DfT is prepared to go to avoid expressing the Regulations in kilometres per hour (km/h) are just perverse.


  2. This might be a good opportunity to push for the universal adoption of speed limits in km/h. In one fell swoop all these problems would be wiped away.


  3. This whole bizarre mess makes me wonder how all the DfT specifications (placement, dimensions of signs, etc.) for road signs were ever done in metric at all (even though it is entirely hidden from the public).

    On the absurdity point: any agency that would specify placement of warning signs in meters from the location of a hazard and then insist that the distance on those same signs read “yards” instead of the true measurement in meters must be “one brick shy of a load” as we say over here!


  4. It is time to make all speed limits in metric, km/h makes more sense than mph.


  5. The other question, is which speed limit will the Police apply? Any new vehicle traveling over the km/h limit would have a vehicle which doesn’t comply with the construction regulations….. Do the police speed guns show km/h?


  6. Philip makes a good point. Are speed detection devices switchable? Would this create its own mess like the weight scales in the NHS? (I can see a lawyer interrogating the police officer in the witness box about how sure they were which units they had set the device to!)

    We always (and quite properly) come back to the same root answer: convert all signs and regulations expeditiously to metric.

    I’m wondering if we’re reaching critical mass when it comes to anomalies and problems that keep arising from hanging on to Imperial road signs. It would be interesting to see the entire case presented all in one place; perhaps that would be the tipping point to convince some key stakeholders that a change in policy must not be delayed any longer.


  7. This strikes me as a follow on to the recent story about the millions spent recently on “super test centres” for motorcyclists because of a new law requiring certain driver tests at 50 km/h which would break the current 30 mph speed limit on roads where the tests would otherwise take place.

    Given that HGV and PSV speed limits aren’t posted seperately on road signs it would seem to make sense to just set the speed limits based on the limiters rather than rounding up to a “hard mph” just for the sake of it. Once again this just seems to be the DfT doing everything they can to make any future change to metric more difficult and expensive.


  8. Why are trucks restricted to 90 km/h anyway — what’s wrong with 100 km/h ?


  9. Those of us who have played around with old style computer cards might remember DIL (Dual in line) switches that were mounted on the card. These switches were used for setting up card addresses and the like.

    If this were applied to police speed guns, then yes, they can be switched between mph and km/h, but only by a technician who would have to open the device up to make the change. The local plod would not be allowed anywhere near the switch.


  10. Here is a link to the story about the super test centres that Alex refers to:

    Here is the part that really strikes me from the Transport Committee report (as paraphrased in the article):

    “The Committee condemns Ministers’ failure to negotiate an exemption from the EU requirement that parts of the test should be performed at 50 km/h or 31.07 mph. MPs argue that it is both bizarre and confusing that tests should be performed at speeds not permitted on the public highway in built-up areas, and that it should be measured in units not commonly used in the UK.”

    The MPs have it the wrong way ’round: what is bizarre and confusing is that signage and all applicable laws pertaining to motoring are not exclusively in metric units.

    Once again, I believe (or at least hope!) we are approaching critical mass regarding the anomalies and unnecessary expense that has its root cause in the UK retaining Imperial units on road signs. Let’s hope enough influential persons, both within and without government, will raise their voices and exercise their influence to finally turn this sorry situation around.


  11. The proposed changes are for more reasons than justfor you people to just moan about km/h and mph, the main reason is due to so many different speed limits, for example a coach unrestricted can do 70mph unless over 40 ft, if coach restricted it can only do 62mph if 40ft, minibuses can do 70mph coach with trailer 60mph coach over 40 ft 60mph and the lorries are even more confusing so DFT quite rightly want to clarify and make this simple as one speed limit.
    The 2nd reason is to make the differential speed gap between cars and lorries smaller meaning safer roads this has been proven within roadworks where average speed cameras use to control traffic at 40mph causing delays, when roadwork speed increased to 50mph as are now, delays were minimalised.


  12. No one is suggesting that the DfT do not have legitimate safety reasons for their proposed changes, or other matters of concern.

    Indeed, as far as km/h are concerned it is not on their agenda at all.

    It remains a fact however that part of the problem is trying to accommodate km/h based limiter settings within a framework of speed limits in mph (hence the odd figure of 62 mph). The point of the article is the unnecessary complexity that arises from this.

    If clarity and simplicity is what they want then the proposal here would provide a better basis for it.


  13. Calvin’s neatly rounded up, but essentially different, imperial equivalent of the 12-metre vehicle length that governs current coach speed limits is a good illustration of what the DfT have done in their proposals to define speed limits in terms of rounded up imperial equivalents of metric speed limiter settings.

    The DfT’s stated intention of aligning all the different commercial vehicle motorway speed limits with speed limiter settings will, as Calvin points out, result in a simplification and reduction in the number of different speed limits. But, by sweeping the km/h-mph issue under the carpet, we will end up with 4 different effective limits, instead of only 2 if commercial vehicle speed limits were to be set in kilometres per hour (km/h):

    90 km/h for newer HGVs
    60 mph for older HGVs
    100 km/h for newer PCVs
    65 mph for older PCVs

    Things would be simpler, and a lot less confusing, if we all used one system of measurement and didn’t distort values by converting them back and forth between different systems.


  14. I’m sure we’ve all seen the speed limit “100” stickers on the back of many UK coaches.

    If the DfT proposals go through, I wonder if some owners of older coaches will advertise their new speed advantage by sticking a “105” sticker on the back of their vehicle.


  15. Given the fact the km is the major unit (outside ring of the speedo dial, trip counter, odometer, tachograph) of vehicles with tachographs (which now means any comercal bigger than a light van (and including them if they have a towbar) it would be far easier for a lorry driver to point the needle at 90km/h than it would be looking for the smaller 60mph mark. For this reason, the drivers of these classes of vehicles will already be pretty familiar with km, so simply setting the limit in klicks shouldn’t cause them much bother, it’d be easier for them. There’s also the considerable bonus to road safety that the large number of foreign registered lorries (some of which seem to pass you with suspiciously high speed limiter settings) should understand the max speed accurately as non UK spec vehicles tend not to have mph marked on their speedometers at all.


  16. Actually, non-UK spec vehicles would never have mph on their speedometers, would they? I presume such vehicles are perfectly legal on UK roadways, yes? So, if bridge strikes are an issue for foreign drivers in foreign lorries, hence requiring dual signage for dimension limits, would it not also behove DfT to use dual signage for speed limits for similar reasons (at least in those areas where the speed limit is less than what the speed limiter would enforce)?

    Yet another safety issue DfT is failing to address in its mad effort to resist metric units with all its might.


  17. I feel that the speed limit should be raised for lorries and buses to 65mph. So less drivers don’t have accidents by falling asleep at the wheel with the drone of the engine at 56mph in hgvs. And maybe more people will use coaches as they will get you to your destination quicker at 65mph. And that should mean less cars on the roads and leave us delivery drivers to have safer roads without cars pulling in front of you. Thank you.


  18. When will the people responsible for these decisions get real?
    Isn’t it obvious that vehicles travelling in one direction at the same speed have to be safer than different types travelling at different speeds? This is exactly the reason so many manoeuvres are made on motorways and in many instances the cause of collisions & crashes on a daily basis on our motorways. The same goes for the antiquated 40mph single carriageway rule with cars overtaking on bends etc due to frustration. Surely upgrading LGV’s to 50mph and downgrading cars from 60 to 50mph has to make these roads safer. We forget, I think, that HGV’s and LGV’s are much more safer and driver-friendly these days and together with the extensive driver training are probably much safer on our roads than most other vehicles.
    Come on Britain. Get a grip. We’re in 2010 not 1950.


  19. I agree same speed limit is best but would not be happy if car speed limits were reduced to accommodate this. For safety all vehicles could not do 70mph. I drive 15 metre single deck coaches (50ft) and 14.5 metre long doubledeck coaches with trailer, and 70 mph for latter vehicle would affect its stability in my opinion. I can only presume this would be the case for large HGV’s. As far as km/h and mph, it don’t bother me what we run by. Can’t ever see km/h ever taking over in GB.


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