How to improve Highway Code 2022

The Highway Code was updated on 29 January 2022. It introduced a hierarchy of road users based on vulnerability and aimed to give priority to the most vulnerable road users. Ronnie Cohen comments.

Last year, the Department for Transport ran a public consultation on changes to the Highway Code. I responded to the consultation and gave them my suggestions for improvements, especially in the use of measurements. Most of them were not adopted. However, the one about dropping conversions to feet was partially adopted. They dropped a few imperial conversions for very short distances. I welcome that. This was undoubtedly influenced by the official social distancing advice being given in metres only. Here I give my own opinions about making improvements to latest version of the Highway Code.

In the Highway Code 2022, they do not give conversions for metres for the shortest distances except for some conversions of body height and some other places where metres appear alone. In a lot of places, the supplement metre measurements with feet. They can be consistent and drop all conversions to feet.

For stopping and thinking distances, they also use car lengths as well as metres and feet. The DfT states that the average car length is 4 metres. Drop the feet and car lengths. Instead of car lengths, they can tell drivers to use the 100 metre distance between marker posts on major roads as a reference for comparing stopping and thinking distances. Unlike car lengths, the distance between one marker post and the next is always the same.

In Rule 92, the Highway Code states “You MUST be able to read a vehicle number plate, in good daylight, from a distance of 20 metres (or 20.5 metres where the old style number plate is used).”. Drop the rule in brackets. Why exactly 20.5 metres and not 20? Are drivers expected to get a measuring tape to measure a distance of exactly 20.5 metres? Surely, any eyesight test with a number plate will be read at an estimated distance of 20 metres.

In Rule 95, the DfT uses an archaic spelling for micrograms. Why? Replace “microgrammes” with “micrograms”.

In several places, the DfT uses the common “cc” for cubic centimetres. They should replace all instances of “cc” with “cm³”. This is the correct symbol for cubic centimetres.

In Rule 253, we see “50 cc (4 kW)”, giving the misleading impression that kilowatts are a conversion for cubic centimetres. The watt (where kilowatts are derived) is the unit of power whereas cubic centimetres express volumes.

Rule 270 is about emergency areas. In this section, an image is shown with an SOS sign and a distance of 300 yards. If that were given in metres, a driver could divide this figure by 100 to work out how many marker posts to pass to reach an emergency phone. Obviously, this would require changes to the road sign regulations to make this legal.

In Rule 277, drivers are given some instructions so they know what to do in an emergency. One of them relates to marker posts and driver location signs. This one tells drivers to “quote the numbers and letters on marker posts or driver location signs which are located along the edge of the road”.

Why doesn’t the DfT explain what these numbers and letters mean? Location information is useful to drivers and is there for their benefit. The AA and Wikipedia do a much better job than the DfT to explain what they mean. In DfT publications intended for the general public, they fail to explain what the information means on marker posts and driver location signs. Is it because the DfT doesn’t want drivers to know that they show kilometres? Is this the DfT’s dirty little secret that the general public is not supposed to know? Could it be that it would undermine their public opposition to the use of metric units on British road signs? No wonder there is such widespread ignorance about them.

Here is a quote from the Direction Signs section:

“‘Countdown’ markers at exit from motorway (each bar represents 100 yards to the exit). Green-backed markers may be used on primary routes and white-backed markers with black bars on other routes. At approaches to concealed level crossings white-backed markers with red bars may be used. Although these will be erected at equal distances the bars do not represent 100 yard intervals.”

Why is there inconsistency in the placement of marker posts (at intervals of 100 metres), ‘countdown’ markers at exit from motorway (at intervals of 100 yards) and white-backed markers with red bars near level crossings (at unspecified intervals)?

The changes I recommend to the Highway Code 2022 are constrained by the need for the Code to reflect the road regulations. The measurement mess in the Code reflects the mess of mixed units on British road signs. If we want to further progress, we need to make more progress on metricating British road signs.

The new version of the Highway Code was published online on 29 January 2022. A printed version is due to be published in April 2022. You can find the online version at

7 thoughts on “How to improve Highway Code 2022”

  1. A lot of this is inaccurate (CC is not is not CM3 ie 3 cubit feet , 3to power of 3 is 9 cubit feet,(50cc is 4 KW) what nonsense ,KW is electrical power and does not apply to engines. Someone should go back to school!


  2. If anyone needs to go back to school it is imperialyes. Everything said is wrong. CC is an abbreviation for cubic centimetres but abbreviations are not used in SI, symbols are and the correct symbol is cm³. None of this relates to feet at all.

    The watt is the unit of all power, not just electrical, but includes mechanical, chemical, thermal, etc as well. All power is measured in watts. Engines are designed and engineered in watts. Mechanical power in watts is equal to exactly the speed in radians per second times the torque in joules per radian or Newton-metres per radian.

    It’s not surprising that imperial supporters lack scientific and engineering knowledge.

    Liked by 3 people

  3. Imperial rubbish
    All engine powers are in kW these days, 1 HP = 746 Watts or thereabouts depending on the actual HP used, and has done so for probably more that a century. I understand that all motor cycle power references are in Watts (kW) on the DVLA V5 registration forms, and correctly so.
    No idea where that cubic feet comes from, I know Americans use cubic inches for engine cubic capacity, but cubic feet are a little on the large side. The cubit was a biblical unit of measure, not used a lot these days.
    Old fogies such as myself do lapse back into cc instead of cm³ at times as with centigrade instead of Celsius, but at least they are reasonably valid variations.

    Liked by 2 people

  4. The Highway Code uses the assumption that a car’s length is 4 metres. I checked a few figures – the current (sixth generation) Ford Fiesta hatchback has a length of between 3.95 and 4,07 metres while its saloon counterpart has a length of between 4,29 and 4,41 metres.

    Liked by 2 people

  5. For the record, one watt is the power (or rate of energy transfer) that is equal to one joule per second; one joule is the energy required to move a mass of one kilogram a distance of one metre against a force of one newton and one newton is the force required to accelerate a mass of one kilogram by one metre per second squared.


  6. There’s never been a need to give bracketed distances in feet for track events in athletics (e.g. Usain Bolt, 100 metres (328 feet) Olympic champion). So, it looks very odd to see this being done in the Highway Code:

    e.g. “Rule 226
    You MUST use headlights when visibility is seriously reduced, generally when you cannot see for more than 100 metres (328 feet).”

    Also, on road signs in the UK, short distances are shown in yards, not feet. So, in the Highway Code, why does the Driver and Vehicle Standards Agency feel the need to convert distances in metres to units that no one in the UK uses for such purposes?

    Liked by 1 person

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