Road signs

For a full presentation of the case for converting the UK’s road signs to metric units, see UKMA’s publication, “Metric signs ahead”, which can be downloaded from this web page. On this web page, we trace the history of the Department for Transport’s (DfT’s) unwillingness to fall into line with Government policy on metrication.

The lack of significant progress on converting road signage in the UK to metric units is perhaps the most obvious and visible example of successive governments’ failure to carry through the changeover which was begun in 1965. To quote the 1972 white paper on metrication:

It had previously been proposed that speed limits should be made metric in 1973 but on 9 December 1970 the Minister for Transport Industries announced in Parliament that this would not be done and that the Government had no alternative date in mind.

(Hansard, 1970, quoted in the White Paper on Metrication of the Department of Trade and Industry, 1972, paragraph 107).

Since then, there has been little progress toward the objective of converting road signs. In 1989 the UK Government secured a derogation permitting the UK to “fix a date” for this conversion, but there was no indication of what that date might be nor even of when the date would be fixed. Indeed, in response to the publication of “Metric signs ahead” in 2006, the DfT made it clear that it had no plans carry out its obligation, which a spokesperson described as “a waste of taxpayers’ money”.

In 2007, the DfT requested the European Commission to propose the complete removal of the obligation to fix a date for converting road signs to metric. The Commission duly obliged, partly on grounds of “subsidiarity”, and the resulting amendment to the Directive was finally agreed in 2009. Contrary to popular myth, there has never in fact been any pressure from the European Union for the UK to convert its road signs, and the amendment has made little practical difference.

Needless to say, this change in EU law in no way detracts from the case for converting the UK’s road signs.

Height and width restriction signs

In September 2009, despite its implacable opposition to general metric conversion, the DfT proposed that within 4 years imperial-only height and width restriction signs (roundels) should no longer be permitted and should be replaced by dual metric/imperial signs. Similarly, imperial warning signs (red triangles) should only be used in conjunction with an accompanying metric sign (The difference between the rules for roundels and triangles is that the triangular shape prevents both metric and imperial units appearing on the same sign).

Some time after the 2010 general election, the DfT dropped plans to make metric units mandatory on restriction signs and to require imperial warning signs to be accompanied by metric warning signs. The regulations that made imperial units mandatory and metric units optional for warning and restriction signs remained unchanged until the TSRGD 2016 came into force on 22 April 2016. On that date, metric units became mandatory for all new height and width restriction signs.

roundel signs
When imperial-only roundel signs (left) are replaced, the dual metric/imperial roundel signs (right) must be used.

When imperial-only warning signs (left) are replaced, the dual metric/imperial warning signs (right) must be used.

Although this move was welcome as far as it went, the DfT had made it clear that it was “a specific solution to a specific problem” (i.e. disproportionate numbers of bridge strikes by foreign lorries) and was not part of any long-term conversion plan. It should also be pointed out that the UN-sponsored Vienna Convention on Road Signs and Signals (an international treaty to which the UK is a signatory) specifies exclusively metres on height, width and length restriction signs.

DfT objections to metric conversion

The DfT’s objections to conversion are longstanding but have changed over the years. The original postponement of the 1973 target was clearly the result of a successful campaign by politicians opposed to metrication generally, but the then Minister was careful not to rule out conversion at some time in the future, and the 1972 White Paper commented that “The change of speed and distance signs to metric units will need to be considered in detail, but not for some years.”

Since then, the objections have been, variously, that

  • Drivers who have not received metric education at school would be confused by a change to metric units (Parliamentary Written Answer, 11 July 2002, Hansard, Col 1116w) Subsequently, it was suggested that conversion might be considered when a majority of drivers had received metric education.
    [Comment: This point has almost certainly already been reached. This is because metric units have been mandatory in state schools since 1974, and therefore all drivers who were born after 1964 will have received their secondary education using metric units. In any case, evidence from other countries’ changeovers demonstrates that such “confusion” is not a significant problem.]
  • Dual signage (i.e. metric and imperial on the same or adjacent signs) would be confusing – and therefore dangerous in a safety-critical environment (quoted from a letter from the Permanent Secretary, 2003).
    [Comment: 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”].
  • As the two previous arguments had lost any validity they might have had, in 2006 the DfT produced a new argument: Cost. They claimed that the cost of conversion, estimated at £680 – 760 million (ca. £1400/sign) would be disproportionate to the benefits for transport and is not a priority for scarce resources.

With regard to the costs argument, several points should be made:

  • Although there are clear benefits for transport, the overwhelming benefit would be to society as a whole, as functioning adults would no longer have to be familiar with two systems of measurement. By insisting on maintaining a separate, stand-alone system for road signs, the DfT bears much of the responsibility for perpetuating the UK’s measurement confusion.
  • The costs have been grossly exaggerated – possibly deliberately. It is palpably absurd to claim that the average cost of amending or replacing road signs is £1400/sign. The DfT is guilty of “shroud waving” in order to protect its budget.
  • 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.
  • All other sectors of the economy have already absorbed the costs of change within their own budgets. Manufacturing industries have retooled their factories, retailers have invested in new scales and retrained their staff, schools have redesigned syllabuses and purchased new textbooks – yet the DfT has continually sought to postpone the inevitable – thereby actually increasing the eventual cost (as any additional new imperial signs will have to be amended or replaced).

This failure to even begin to plan for metric conversion of road signage is particularly serious and indeed wasteful since, if such a plan existed, any new imperial signage could be installed in a way that minimised future conversion costs. An example of the DfT’s wasteful approach is the installation on motorways of electronic variable speed limit signs that are not capable (without amendment) of showing the three digits that could be needed to display higher speed limits (e.g. 100 km/h).

Digital speed limit sign

This variable speed limit sign cannot accommodate more than two digits without modification – hence can only show speed limits up to 90 km/h

Digital speed warning sign

Even worse are the LED speed limit signs activated by drivers, which are not capable of amendment, as in the example above.

UKMA therefore calls upon the UK Government without further delay to announce the date when the UK’s road signage (and hence speed limits) will be converted to metric units. (This date should be as soon as reasonably possible, taking into account the time required to pass the necessary legislation and physically replace or amend the imperial signage. Based on other countries’ experience, it is believed that this date could be within three to five years of the announcement.

As indicated above, UKMA considers that the conversion of distance signage could (as in Ireland) be spread over an extended time period, but we do not favour a long transitional period during which both imperial and metric signs are in place. We are particularly opposed to the erection of new distance signs displaying both units on the same sign as we feel that such signs would become permanent and drivers would have no incentive to adjust to metric units. Whether the changeover should be by totally new signs or by amending existing signs is a matter for detailed consideration.

Distance signs
Many existing signs can be easily amended with overlays or riveted plates

The changeover arrangements should also include the use of the correct international symbols, including “km/h” to denote “kilometres per hour”. In particular, the erection of further signs giving “m” as an abbreviation for “mile” should be prohibited with immediate effect.

The changeover programme will also need to include legislation to revise speed limits, revision of various Regulations, including the Traffic Signs Regulations and General Directions (TSRGD) and the Road Vehicles (Construction and Use) Regulations to require legible “km/h” on speedometers, together with an intensive campaign of driver education shortly before and during the changeover.