British metric road signs: An overdue changeover

As part of the metrication programme, British road signs were originally intended to be converted to use the SI international metric system in 1973. However in 1970 the newly elected government put road signs metrication on hold, where it has remained ever since. Currently the information on British road signs is mostly imperial, with only limited usage of metric units.

Weight limits (to be precise mass limits) are metric and measured in tonnes, albeit rather confusingly with “T” used for tonnes. "T" is the correct symbol for teslas, and the correct symbol for tonnes is “t”, as used in both school and in science/engineering.

Another instance of the irregular usage of symbols is “m” being incorrectly used to denote miles on many signs (including motorway exit and service signs), whereas we are taught at school that “m” is the symbol for metres.

It is only the information on the signs which are imperial. Everything else about the road networks is metric, because road construction, sign manufacturing and positioning, are all done using metric measurements. The emergency marker system on motorways is all metric as well. Distances are surveyed and measured in metric (including using the all-metric Ordnance Survey map as well), but regulations force contractors to convert to imperial. Presumably the original height restrictions are also worked out in metric, yet have to be converted to imperial every time.

All these unnecessary extra calculations must surely waste contractors’ time, and who knows how much extra this adds to costs? As well as this, there is a danger of conversion errors, which could compromise safety in extreme cases.

In fact, not using metric is at best wasteful, inconvenient and costly, and at worst dangerous. There have been instances of bridge strikes due to not using metric on restriction signs at all. Drivers both sides of the Northern Ireland-Republic of Ireland land border have to constantly switch between km/h and mph. People educated in metric, including myself, are forced to use imperial units despite having never encountered it at school. And visitors from the rest of Europe coming in their own vehicles, who will have metric only speedometers and odometers, have to follow imperial speed limits and must be bewildered. Even the Highway Code itself shows stopping distances in metres and visibility in metres for example, and yet metres are not authorised on distance signs.

And what about the vehicle manufacturers? The insistence on retaining mph and miles means that the UK has dual-unit speedometers (mph primary, km/h secondary - both currently required by UK law), and odometers in miles. Only the USA also requires such speedometers and odometers as well, and presumably Myanmar and Liberia as well. The rest of the world has km/h only speedometers, and km odometers. Does anyone think that vehicle manufacturers are going to meet the UK and US requirements for free? Of course not. For vehicle manufacturers, maintaining two lines of production - metric and imperial - surely costs them money, with the costs passed on to you and me, the consumer.

Vehicle manufacturers work exclusively in metric so provide vehicle dimensions in millimetres (easily converted to metres) in the vehicle owner manuals, so why are metric only height, weight, and length restrictions not allowed?

All the problems above can be solved simply by converting the road signs to metric, and this mean that Britons can use metric for all purposes, think in metric, use what they learn at school reinforcing what was learnt at school, and everyone will benefit from much clearer and easier to read road signs. The easier and quicker the road signs are to read, the better it is for safety.

The UK Metric Association (UKMA) published the Metric Signs Ahead report in 2006 which called for such a metrication of road signs, and estimated the conversion costs to be £80 million over five years, including a rapid changeover for speed limit signs, ideally overnight. The estimated £80 million was nothing compared to the roads budget at the time of £7 billion (which in itself is far too little but that is another issue entirely). This call for metric road signs was reported in the news, including on the BBC and the Guardian.

Unfortunately the UK Department for Transport (DfT) gave a hostile response to Metric Signs Ahead claiming they had “absolutely no plans” for metric road signs, and later presented a ridiculously over-inflated estimate of between £680 million and £760 million. UKMA's response to this serious over-estimate is included here.

The DfT have changed their excuse for not metricating road sign information from “too confusing for older drivers” (used in the 1980s and 1990s) to “too costly” (used since 2006). This would be news to Australia, Canada, South Africa, India, and Ireland. All these countries managed to change their road signs to metric at a reasonable cost, without waiting until the public was majority metric educated, and without any reports of casualties. Australia managed to change over without any problems even with vast majority of cars in Australia having all-imperial speedometers and odometers before the changeover. The lessons learnt from these experiences to can be applied to achieve a smooth changeover in the UK.

Recently, a UK traffic signs review has been launched by the DfT. The DfT have produced a draft report (a draft action plan) which does mention a TSRGD (Traffic Signs Regulations and General Directions) consultation coming up in September 2009. Unfortunately in this draft report there is not a single mention of going metric, and also fails to address the fact that there are too many long winded wordy signs (when simple graphical signs would have sufficed), and the fact that many signs are language specific. Indeed the UKMA's response to the DfT's draft report mentions these points and calls the draft report a draft inaction plan.

The UKMA have produced a Traffic Signs 2.0 leaflet in response. I wholeheartedly agree with the suggestions for improvement mentioned in this leaflet, and it is clear from the images that the recommended metric only signs are infinitely more language independent, easy on the eye, often smaller and therefore cheaper to maintain.

With a well managed and rapid changeover the UK can also change over problem-free, safely, economically, and people of all ages will be able to adapt quickly with the right support and the right amount of publicity at the right time. The UK needs metric road signs now, and the government needs to start planning for this now. The UK will benefit enormously.