DfT myths and reality

Over the years, the UK Department for Transport (DfT) has come up with many arguments in support of successive Transport Ministers’ reluctance to convert UK road traffic signs from an outdated and poorly understood system of measurement to one that is simple, logical and almost universal. Ronnie Cohen puts forward counter arguments.

DfT Myth 1: Drivers need metres converted to feet and inches on height, width and length restriction signs.

The DfT does not explain why the feet and inches are still needed on such signs. The DfT insist that they must still be used. Yet, oddly, metres appear alone in some places in the Highway Code, and drivers are expected to understand them! The private sector uses height restriction signs for car parks and petrol stations and they are overwhelmingly metric (with no imperial conversion). These metric-only signs are widely used by the private sector and can be found everywhere. Drivers seem to have no problems with such signs.

DfT Myth 2: Road traffic signs are inherently local in their scope.

When we see all the areas of British life where miles are used, there can be no doubt about the enormous influence of the units used on road signs. Why are miles so widely used in the UK? Because that is what the British use on their road signs. It affects the way that Brits think about long distances and speeds. That influence goes far beyond transport, as I described in a previous MV article (see metricviews.org.uk/2016/12/dft-influence-goes-way-beyond-transport/). So how can the DfT believe such a claim?

If you want to see further evidence of the link between units on road signs and their use in society, look at where English miles are still widely used. Mainly in the UK and USA, the only two major countries that still use them on their roads.

DfT Myth 3: Costs of metricating road signs would far exceed the benefits.

In its standard responses, the DfT claims “The significant costs involved for the UK in changing the measurements used on signs, replacing signs, providing safety and publicity material and the consequential costs for businesses and other organisations would far exceed any benefits in terms of meeting the EU’s objectives.”

When I asked the DfT what studies they have done on the benefits of a full metrication programme for UK road signs, they admitted that they have neither carried out any study of nor considered the benefits of “a full metrication programme for UK road signs” (see http://metricviews.org.uk/2017/08/dft-has-done-no-cost-benefit-analysis-on-metrication-of-road-signs/). Without knowing the benefits or what they are worth, the DfT has no basis for this claim.

DfT Myth 4: Metricating road signs is about meeting the EU’s objectives.

The DfT claims “The significant costs involved for the UK in changing the measurements used on signs, replacing signs, providing safety and publicity material and the consequential costs for businesses and other organisations would far exceed any benefits in terms of meeting the EU’s objectives. The principle of proportionality requires that action at Community level does not exceed what is required to achieve the EU’s objectives and clearly consideration must be given to ensuring that costs are not disproportionate to overall benefits.”.

No. The original plans to convert road signs were part of the UK Metrication Programme that started in 1965 at the behest of British industry. In the late 1960s, firm plans were made for metrication – with a target date of 1973 for converting road signs. However, following the change of government in 1970, the Minister for Transport Industries, John Peyton, postponed the target date, which has never been reinstated. This all occurred before the UK joined the Common Market, the forerunner of the European Union.

DfT Myth 5: The metrication of traffic signs would divert funding from high priority areas.

Imperial units can be phased out over several years for most traffic signs when they need to be replaced without any additional spending over normal maintenance (e.g. distance signs, vehicle dimension signs, etc.). Changes to the TSRGD would be needed to authorise metric units on these signs.

In 2006, the UK Metric Association published the “Metric Signs Ahead” report on the metrication of British road signs. (Source: UKMA, http://www.ukma.org.uk/sites/default/files/MSA.pdf) This report estimated that the cost of amending or replacing half a million road signs would be in the range £41 – 160 million, with a “most probable” figure of £80 million, some of which would be absorbed within annual revenue budgets. This is equivalent to £82 – £320 per sign with a “most probable” figure of £160 per sign. This would be a tiny proportion of the total transport budget and could be spread over several years.

My own research found actual costs for road signs were much closer to the UKMA than the DfT cost estimate of £1400 per sign (see http://metricviews.org.uk/2012/05/dft-cost-claims-busted/). Even if the DfT cost estimate were credible, it is still a tiny proportion of total transport expenditure and is capable of being spread over several years and partially absorbed within existing budgets.

DfT Myth 6: Units on road signs should only be changed to improve safety.

The DfT says that “The Department’s view is that displaying dual measures of height, width and length restrictions make it easier for drivers and are designed to help improve safety on our roads.” and “We do not consider that diverting funding from high priority areas for the metrication of traffic signs is justified – not least as there is no evidence that the use of the mile presents a safety risk to road users.”

This is the same government department that resists the use of metres on emergency exit signs in tunnels. They require them to be signed in yards, which foreign drivers are unlikely to understand. For several years, the DfT has resisted making metric units mandatory on vehicle dimension signs. For example, see Robin Paice’s article, “DfT admits: no basis for blocking metric signs”, http://metricviews.org.uk/2012/03/dft-admits-no-basis-for-blocking-metric-signs/, published in 2012, despite all the safety issues raised in DfT consultations on imperial-only vehicle dimension signs.

DfT Myth 7: Units used on road signs is just a transport issue.

The DfT replies to demands for metrication show that they just see units on road signs as a transport issue. It is not. The measurement muddle still affects many areas of British life.

As I described in a previous article, the influence of units on road signs goes far beyond transport (Source: http://metricviews.org.uk/2016/12/dft-influence-goes-way-beyond-transport/). I identified many areas of British life where miles are commonly used and how British citizens and the media think about and describe long distances and speeds. For example, the digital display boards at the French Open show ball speeds exclusively in km/h (the French do not use miles!) but the French Open tennis commentators still felt obliged to convert these ball speeds to miles per hour for the British audience.

The DfT and successive transport ministers seem to believe that the units on road signs can remain non-metric while the rest of society goes metric. The British experience shows that the notion that road signs can be a stand-alone system that is separate from the rest of society is nonsense.

DfT Myth 8: Drivers without metric education would be confused by a change to metric units on road signs.

The DfT made this claim until the UK passed the point when a majority of drivers got a metric education. After that, the DfT switched to cost as the justification for their failure to metricate road signs. When I asked the DfT what evidence they had to support this claim, they admitted that they had none. You can find details about this in my previous article, “DfT guilty of making unfounded claims” (Source: http://metricviews.org.uk/2013/05/dft-guilty-of-making-unfounded-claims/).

DfT Myth 9: Imperial units on road signs can be an independent stand-alone system.

As far the DfT and transport ministers are concerned, the rest of society can go metric while road signs should be exempt from metrication. The DfT is primarily responsible for perpetuating the current measurement muddle that Britons experience on a daily basis, not just in transport but in numerous areas of British life. The imperial units used on road influence continued usage of these units in British society and the media. One only has to look at the aspects of British life where miles, yards, feet and inches are used to see how much these units on road signs influences common usage. The notion that the imperial system for road signs can be an independent stand-alone system that is separate from the rest of society is and always has been nonsense.

DfT Myth 10: The cost of amending or replacing around ½ million signs would be in the range £680 – 760 million.

The DfT made this estimate in 2006. It is based on the following dubious assumptions (Source: UKMA, http://www.ukma.org.uk/sites/default/files/MSA.pdf, see MSA 2009 Update section):

  • All work will be carried out in a single year, not spread over several years (as in Ireland).
  • All sign changes will incur costs of “traffic management” of
    £271 – 309 per sign, unlikely in most cases.
  • All “route confirmatory” (i.e. distance) signs will need to be replaced rather than amended (unlike Ireland).
  • 25% has been added for “supervision, preparation and design” for a simple repetitive operation.
  • 45% – 65% has then been added for “optimism bias”, inappropriate in this case.

I investigated the actual costs of installing, replacing and amending signs in 2012 by asking a few dozen local authorities how much they spent on doing this and how many new signs they installed and how many they replaced. I looked at media reports and ministerial replies. These actual costs were all far lower than the DfT estimates (see http://metricviews.org.uk/2012/05/dft-cost-claims-busted/). The Irish conversion programme cost much less than the DfT estimates. The DfT figures are grossly inflated.

DfT Myth 11: Dual signage would be confusing – and therefore dangerous in a safety-critical environment.

The DfT once claimed that dual signage (i.e. metric and imperial on the same or adjacent signs) would be confusing – and therefore dangerous in a safety-critical environment. This is quoted from a letter from the Permanent Secretary in 2003.

However, distance signage is not “safety-critical”; speed limits would obviously NOT be dual signed; and the DfT already authorises dual units on height and width restriction signs – which ARE “safety-critical”.

DfT Myth 12: The metrication of road signs is a “a waste of taxpayers’ money”.

In response to the publication of “Metric signs ahead” in 2006, a DfT spokesperson described as “a waste of taxpayers’ money”. The DfT has never explained why other countries (e.g. Ireland, Canada, Australia, New Zealand, South Africa) have found the metrication of their road signs to be worthwhile and has not considered the benefits to the UK of such a project. Instead, it has given unconvincing excuses for inaction. Its latest excuse is its grossly inflated cost estimate.


The DfT and successive Transport Ministers since 1970 have been out of step with the modern world regarding the UK’s continued use of medieval units on road signs. In its support of Ministers’ short term political objectives, the DfT has, alas, often had to ignore reality, thereby reducing its credibility on this issue.

7 thoughts on “DfT myths and reality”

  1. What’s going to happen when cars have technology that will read signs and British cars are programmed to mph you suddenly go on holiday to the continent you get off the ferry or train then suddenly your driving at 110mph on a motorway instead of 110km/h how long before thousands of tourists are arrested for speeding? I am also thinking this could happen in the U.K but reversed as continental drivers suddenly drive too slow for British roads.


  2. I cannot understand why the DfT is so hostile to metricating the road signs. The road signs have been metricated in Australia, New Zealand, Canada, the Irish Republic and South Africa without all this drama.


  3. My wife and I recently bought a new car with all the fancy gadgets built-in. These included devices for detecting the white lines on the roads (and beeping if you drifted over them), devices for detecting cars on either side of you, devices for detecting obstacles in front of you and behind you and finally a device that would read and interpret speed limit signs. These devices all point to the development of the driverless car.
    If applied to Ireland, the speed limit device is scary. Many minor border crossings between Northern Ireland and the Republic are marked only by a 80 km/h sign (entering the Republic) or a “National Speed Limit” sign (entering Northern Ireland). Sometimes there are no other “give-aways”. If the car was interpreting road sings, how would it know that it has to suddenly “think” in kilometres? What about if the car goes to France? The “km/h” give-away on French signs is missing. If driverless cars are to become a reality and people are going to use them to cross borders, then either there will be a massive burden on car manufacturers to “teach” their cars about the borders or we will need to harmonise road signs (which include the units used for speed limits).


  4. It really seems like converting road signs would be an investment that pays off handsomely for the UK.

    PM May wants to make a good deal with the EU as part of Brexit and to be a strong and vibrant global trading partner around the world. Other than the USA what system of measurement does she expect those trading partners to be using (and much trade with the USA also uses metric).

    Think of the good will for a trade deal and for resolving the issue of the border between NI and the Irish Republic that would flow from such a visible commitment to reducing trading friction by converting road signs to metric.


  5. The failure of the DfT to move with the times has a muddled effect on other aspects of transport.
    Having recently purchased a one year old small car from a national dealership, an option on the multifunction display shows miles per gallon. Given that gallons of fuel have not been available in the UK for over 30 years what is the point of this obsolete measurement, maybe some one from any car manufacturer can inform us.
    I have now changed the display to read l/100 km, my preferred option.


  6. Another one of DFT’s little myths: throughout Traffic Signs Manual, the authors repeatedly spin that metric distances are ‘forbidden’ by TSRGD. This is a deceit bordering on dishonest, IMO—recent versions only says which formulations are blanket authorised (specific subset of imperial, probably unchanged since 1964) and not what isn’t (everything else). It makes no mention of metric distances at all. There is no excuse for not knowing this, both documents being written by the same team. But until quite recently they could pull the wool over everyone’s eyes by the relative difficulty of obtaining verbatim copies of the statutory instrument. In truth, there is probably nobody discouraging them from rewriting this at any time—it is only prevented by their own idleness, cowardice and prejudice.

    The quote about ‘consequential costs for businesses and other organisations’ would be laughable if it weren’t so mendacious. What costs for private businesses? There would, in fact, be massive savings from not having to work around the dual nonsense and imperial primary which hardly anyone of working age understands any more. The only ‘other organisations’ which matter are highway authorities. As UKMA-obtained consultation responses from many of them show, they’ve been begging DFT to drop the imperial for years. The reality is that DFT most likely have tens (surely not hundreds?) of permanent full-time employees maintaining this charade which would be difficult to justify if the signs were metricated.


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