Road signage mess

One of the most visible signs of Britain’s measurement mess is road signage. This page illustrates some of the most striking problems.

Traffic signs are out of step with industry and education

Britain’s industry was one of the key drivers behind the government announcing its changeover to metric in 1965. With very few exceptions industry uses metric and motor manufacturers are no exception. The vast majority of vehicle handbooks give dimensions in metric.

However, Britain’s anachronistic traffic sign regulations require the use of feet and inches with optional metric for vehicle dimension signs installed before 22 April 2016, the date when the new Traffic Sign Regulations and General Directions (TSRGD) came into force. This mess is illustrated by the picture below showing a typical London street scene.

Back of bus

Look at some of the details:

18 metre length warning sign

Manufacturer’s data for this Citaro “bendy bus” is metric. Not surprisingly this is reflected in the warning sign.

40ft length restriction

A new version of Britain’s Traffic Sign Regulations and General Directions (TSRGD) came into force on 22 April 2016, which require two length vehicle dimension signs to be shown alongside each other, one in imperial units (feet and inches) and the other in metric units (metres). However, solitary imperial vehicle dimension signs can remain in place untill they become life-expired or until they are replaced. Whereas the motor industry works in metres, the Regulations insist on mandatory height and width vehicle dimension signs showing both metric and imperial units and on metric and imperial length vehicle dimension signs to be shown alongside each other.

Learning Pays Billboard

An ironic reminder of the lack of joined-up government policy is given in Newham College’s advertisement at the back of the bus. The government has required metric to be taught in schools since 1974 – yet the same governments have largely forbidden metric units from road signs. Why can’t children practise what they have learned?

Unnecessarily cluttered signage

In a few cases (width and height prohibitions and warnings), current regulations that came into force on 22 April 2016 state that both metric and imperial units must be shown on the same signs (imperial-only width and height prohibition and warning signs can remain in place until they become life-expired or replaced). The result frequently is cluttered signage.

cluttered sign

This cluttered sign uses no less than four units:

  • feet and inches are used to show imperial height
  • metres are used to show metric height
  • yards are used to indicate distance to the bridge.

A purely metric sign could be as simple as


with only one unit required – metres – instead of four. (There is no real need to explain that it is a low bridge – what else would it be? It simply adds to clutter). The revised sign is much easier to read and cost savings could also result since a much smaller sign would be used.