Eight years after the Traffic Signs Regulations and General Directions (TSRGD) were updated to require all new vehicle restriction signs to show vehicle width and height restrictions in both metric and imperial units, the Department for Transport’s Traffic Signs Manual (TSM) has still not been fully updated to take account of the fact that new imperial-only vehicle restriction signs are no longer authorised.

Whilst most other chapters of the Traffic Signs Manual have been updated since 2016, Chapter 8 Part 1 has not been updated since 2009. It includes diagrams for both imperial-only width and imperial-only height restriction signs for use in road works and temporary situations – signs which were legal back in 2009, but have not been authorised for new sign installations since 2016.

Vehicle restriction signs included in the current TSM – Chapter 8 Part 1, page 98

The Traffic Signs Manual contains guidance for traffic authorities on the use of traffic signs and road markings. By failing to fully update it in a timely manner, the Department for Transport stands open to the accusation that they have been promoting the use of unauthorised imperial-only road signs for the last 8 years.

click on the image to access the pdf

The diagram for weight restriction signs is also obsolete as it includes the now unauthorised upper case “T” symbol to represent tonne. The diagram for this sign was corrected to show the lower case “t” in the 2011 amendment to the TSRGD.

629A 629.2A 622.1A

Vehicle restriction signs in the current TSRGD

Whilst diagrams in publications for the general public, such as The Highway Code and Know Your Traffic Signs, were updated long ago, it is inexplicable that guidance for authorities that install road signs should not also have been updated.

UKMA would be interested to hear from readers of any cases that they might be aware of in their area where imperial-only restriction signs have been installed since 2016, and would encourage writing to the relevant highway authority asking for such signs to be replaced with legal dual-unit signs in order to avoid possible legal ramifications.

Mondopoint is a footwear sizing system based on the foot length and linear width of the foot and is measured in millimetres. It is part of ISO standard 9407:2019, which describes the specification for Mondopoint system of sizing and marking. 1 It has the potential to replace various mutually incompatible shoe sizing systems used in different countries. Most of these systems use arbitrary numbers that do not relate to anything obvious. Even worse, different sizing systems are often used for men, women and children.

Several shoe size conversion websites exist to convert between the various shoe sizing systems used in different parts of the world. The shoesizes.co and convertyourshoesize.com websites list most of the major shoe sizing systems in use. 2 3 They include the British, American, European, Australian, Japanese, Chinese and Russian shoe sizing systems. The numeric sizing systems tend to use separate ranges for men and women. So, men’s and women’s shoe sizes tend to be different for the same foot length in numeric sizing systems.

The Europeans use the Paris Point system with sizes increasing by ⅔ cm for each size. The British and Americans use the Barleycorn system with sizes increasing by ⅓ inch for each size. 4 One feature that complicates matters is that men’s, women’s and children’s shoe sizes can have a different zero point, so a particular foot length corresponds to different shoe sizes in these categories. Interestingly, the Chinese have two shoe sizing systems. 5 The old Chinese national standard uses numeric sizing, which is similar to European sizing, which is still common in China. The new Chinese national standard uses a length-based measurement based on millimetres. The Koreans also use millimetre-based measurements for shoe sizes. The Japanese tend to use length-based shoe sizes based on centimetres.

Mondopoint is based on the metric system and is a world standard. It is based solely on foot length and this system also includes foot width. Therefore, a Mondopoint value of 290/120 for a pair of shoes indicates a foot length of 290 millimetres and a foot width of 120 millimetres. The “mondo” part of the name is derived from the Latin word for world. Variants of this word are found in several European languages that are descended from Latin.

It would be much easier if all countries adopted Mondopoint for shoe sizes and abandoned arbitrary numeric sizing systems. Mondopoint is already in official use in Russia, China, Japan, Taiwan and South Korea and is also used by NATO and the military, and now widely used in the sports sector. 6 This would make the countless shoe size conversion charts and calculators unnecessary. Unlike arbitrary numbers in shoe sizing systems used in much of the world, numbers in Mondopoint are transparent – they mean millimetres. In the Mondopoint system, you can measure your feet with any metric measuring tape or ruler to find out your shoe size, unlike the arbitrary shoe sizing systems in current use.

Sources

1. https://www.iso.org/obp/ui/en/#iso:std:71594:en
2. http://www.shoesizes.co/
3. https://www.convertyourshoesize.com/
4. https://goodcalculators.com/shoe-size-converter/
5. https://www.sopicks.com/blog/international-shoe-size-conversion-chart
6. https://www.calconi.com/en/shoe_sizes/guide/mondopoint_shoe_sizes.php

Further Reading

• https://en.wikipedia.org/wiki/Shoe_size
• https://size-charts.com/topics/understanding-shoe-sizing/

HM Government looked at the case for and against the use of dual unit road signs as an intermediate step in the metrication of road signs in the second half of the 1960’s. Three different methods for dual unit sign conversion were evaluated and some technical issues related to dual unit signs were discussed. The findings and illustrations from the National Archive papers are presented here.

Method 1

A separate new sign indicating the speed limit in km/h can be mounted below the existing mph sign without any units as shown in the following diagram:

Illustration for Method 1

This method would be applicable to both terminal and repeater signs. After a suitable period of time had elapsed, the top sign could be dismounted and removed for scrap and the bottom sign could be moved up into position.

Three advantages were given for Method 1:

1. During the changeover period, it would be clear that where one sign only was displayed, it meant mph and where two were displayed, the metric equivalent was shown below.
2. No other additional plates would be required.
3. Symbols would be very legible being the same height.

Two disadvantages were given for Method 2:

1. Very expensive because all new signs would be required, and the only credit would be the scrap value of existing signs – some of which may be fairly new.
2. At least three operations at the site of each sign would be required, i.e. (a) mount 50 sign below 30 (b) remove the 30 sign and (c) shift 50 sign to new position.

Method 2

An insert showing km/h could be made, either below the sign or within the sign. These two options in Method 2 were classified as 2(A) for a separate insert below the sign and 2(B) for an insert within the sign. In both cases, the insert could be made to fit existing signs showing the new figure in km/h.

Method 2(A)

A plate would be required below showing km/h to let motorists know the sign had been altered. Repeater signs could be treated in the same way. An example of Method 2(A) is shown here:

Illustration for Method 2(A)

The advantage for Method 2(A) is that it is cheaper than Method 1 in materials. It requires a smaller, lighter disc and fittings would be required for one small plate only.

The disadvantages for Method 2(A) were:

1. It requires three operations for each sign. These operations are fitting the new figure insert, fitting a supplementary plate and removing the supplementary plate.
2. The cost of the supplementary plate is a complete loss except subsequent value for scrap.

Method 2(B)

The other option for the insert is to put in inside the sign as shown here:

Illustration for Method 2(B)

The advantages of Method 2(B) are:

1. It is cheaper than Methods 1 and 2(A).
2. Only two operations are required. They are to fit the figure insert and subsequently to delete or remove the km/h symbol.

The disadvantage of Method 2(B) is that the km/h symbol might not be completely legible and might fail to indicate that the sign had been changed, especially on repeater signs.

Method 3

Method 3 inserts the km/h figure into the same sign as the mph figure. It was suggested that mph is the top figure and km/h is the bottom figure to indicate that it “was 30 mph and is now 50 km/h”. The specific numbers are just examples. It is possible for the numbers to be reversed but numbers are read from top to bottom. Subsequently, the plate could be salvaged and fitted with a sign face indicating the figure in km/h only. An example of such a dual sign with both figures on the same plate is shown below.

Illustration for Method 3

The advantage of Method 3 is that there should be no doubt at all that the sign has been altered.

The disadvantages of Method 3 are:

1. The figures are smaller than normal.
2. It is slightly dearer than Method 2(B).
3. The method will not be really applicable to repeaters because the figure sizes in that case would be too small. Method 1 or Method 2 would need to be adopted for repeaters.
4. It involves three operations. They are fitting the new 30/50 plate, removing the 30/50 plate and fitting the new 50 plate.

Technical Details

Further technical details on what is involved in practice for the metric conversion were provided in a paper published in February 1969, which is shown here.

Questions were asked about the adoption of the 24-hour clock for waiting restriction plates and confusion arising from the use of ‘m’ for metres and miles.

Conclusion

HM Government concluded that all methods cost a lot in terms of labour and materials. Some methods are more expensive than over in terms of materials and the amount of work involved. The government favoured Method 2(B) as the cheapest option in each respect. Adding km/h would indicate that the sign has been changed and remove any doubt that the speed limit is in km/h and not mph. It can fill all the available space. In case there is not enough room, alternatives suggested were using distinctive colours for the figures or for the whole background within the red border. A recommendation was made to investigate Method 2(B) in much greater detail as a firm basis for future action.

The government was open-minded about using dual units as an intermediate step for the metrication of road signs and suggested further investigation to examine the merits of this approach.

The 1824 Weights and Measures Act introduced imperial standards based on physical objects with certain characteristics, such as the Imperial Standard Yard, and a single set of volume measures based on the new Imperial Gallon for dry and liquid measures to replace several that were in existence. To mark 200 years since the passing of the 1824 Weights and Measures Act, I look at the main features of the Act and ask whether it was a help or a hindrance on the path to metrication in the UK.

The Imperial Standard Yard was introduced and defined as the “Straight Line or Distance between the Centres of the said Two Points in the said Gold Studs in the said Brass Rod, the Brass being at the Temperature of Sixty-two Degrees by Fahrenheit’s Thermometer”. This referred to the straight brass rod in the custody of the clerk of the House of Commons. This yard served as the base unit in the imperial system whereby the other units of imperial length were defined as parts or multiples of the Imperial Standard Yard. Units of area were defined with reference to the yard or derived units of length.

The Standard Brass Weight of One Pound Troy Weight in the custody of the clerk of the House of Commons served as the base unit of weight from which the other imperial units of weight were defined. This weight was called the Imperial Standard Troy Pound. The definition used for recreating it, in case it is lost, destroyed, defaced or damaged in some other way, was “a Cubic Inch of distilled Water, weighed in Air by Brass Weights, at the Temperature of Sixty-two Degrees of Fahrenheit’s Thermometer, the Barometer being at Thirty Inches, is equal to 252 Grains and 458 thousandth parts of a Grain, of which, as aforesaid, the Imperial Standard Troy Pound contains 5760″.

The Act introduced the Imperial Standard Gallon as the standard measure of capacity for liquids and dry goods not measured by heaped measure. The Imperial Standard Gallon was defined as “Ten Pounds Avoirdupois Weight of distilled Water weighed in Air, at the Temperature of Sixty-two Degrees of Fahrenheit’s Thermometer, the Barometer being at Thirty Inches”. The other imperial measures of capacity were defined as parts or multiples of the Imperial Standard Gallon.

Let me explain the difference between the troy and the avoirdupois systems for readers who are unfamiliar with these different weights. A troy ounce is one-twelfth of a troy pound, a pennyweight is one-twentieth of a troy ounce, and a grain is one-twenty-fourth of a pennyweight. Hence, one troy pound is equal to 5760 grains. One avoirdupois pound is equal to 7000 grains. An avoirdupois ounce is one-sixteenth of an avoirdupois pound, and a dram is one-sixteenth of an avoirdupois ounce.

The Act defined the standard for heaped measure for coals, culm (waste coal), lime, fish, potatoes, fruit and all other goods and things commonly sold by heaped measure. The heaped measure was the bushel, defined in the Act as eight imperial standard gallons. The heaped measure contained 80 pounds avoirdupois of water, made round with a plain and even bottom, and being 19½ inches “from Outside to Outside of such standard measure as aforesaid”. The Act stated that such a bushel shall be heaped in the form of a cone at least six inches tall. Anything not sold by heaped measure must be sold by the imperial standard of weight or measure.

These defined measures came into force on 1 May 1825. Section 23 of the Act repealed numerous archaic Statutes, Ordinances and Acts that relate to weights and measures.

To some extent this Act gives the lie to the fantasy that Britain’s imperial measures are ancient. They were standardised no more than 40 years before the first of decision to metricate, even though that was to come to nothing for another hundred years.

Despite the Act’s attempt to set standards for the primary units and repeal arcane laws, it did not radically change the multiplicity of customary weights and measures used throughout the country. Indeed, it expressly states that “it shall [be] lawful [to] buy and sell goods and merchandize (sic) by any weights or measures established either by local custom or founded on special Agreement” provided their exact relation to the standard units defined by the Act was generally known.

The 1824 Act standardised and clearly defined many existing weights and measures throughout the UK and replaced various capacity measures with one (i.e. one imperial pint, one imperial gallon, etc). They became the standard weights and measures that were used across the British Empire. Meanwhile, France adopted the metric system in the late eighteenth century after the French Revolution. Other European countries followed suit during the nineteenth century. As the imperial system was the standard measurement system across the Empire, the British hesitated to adopt the metric system. These factors seem to be major obstacles to the adoption of the metric system. The British have had difficulties with metrication ever since. Why have the British been unable to fully adopt to the metric system unlike the rest of Europe?

You can find a full copy of the 1824 Weights at Measures Act at https://www.legislation.gov.uk/ukpga/1824/74/pdfs/ukpga_18240074_en.pdf.

On the history of metrication, see https://en.wikipedia.org/wiki/Metrication and https://ukma.org.uk/what-is-metric/uk-progress/uk-metric-timeline/.

Twenty years have passed since the UK Metric Association published “A Very British Mess” (VBM). To mark the twentieth anniversary of the publication of VBM, I look at what has changed since its publication in 2004.

Section 2.6 (a) on page 13 in VBM states, “British Standards utilise the watt as the unit of power. However, product documentation still frequently expresses power in horse power (HP) for engines or British thermal units per hour (BTU/h) for central heating boilers.”.

I have checked the specifications recently to see if these units are still used for engines and central heating boilers. Horsepower is still used for engine specifications, especially for vehicles. British thermal units have mostly disappeared for boiler specifications. Boiler specs now use the watt (and its derivatives, e.g. kilowatt) instead.

Section 3.3 (h) on page 18 in VBM states, “Many supermarkets advertise exclusively in imperial even though goods must be priced and weighed in metric at the checkout.”.

The use of imperial units by supermarkets in advertising and pricing has disappeared. Pricing and advertising by supermarkets are now exclusively metric though you may still see imperial units in product descriptions.

Page 22 of VBM shows a Mail on Sunday headline referring to a price increase on a gallon of petrol.

Gallons have disappeared from press reports on petrol prices. These days, litres are used exclusively in such reports.

Page 28 of VBM shows the price per lb for loose bananas.

Pricing per lb has disappeared in all the major supermarkets but is still common in small shops. Major supermarkets show prices exclusively in metric units today.

It is depressing that these are all the changes I could find compared to the situation described in VBM. Apart from these changes, the rest of the points made by VBM still apply today. These are my observations of the current situation today.

When a retailer weighs out his product in front of the customer, can the customer trust the scales? It is usually up to local government to certify the accuracy of such scales, though in recent years, certification of measuring devices within much of the world has been privatised with various countries’ national laboratories overseeing the certification process.

With the advent of digital weighing devices, the increased sensitivity of devices has become an issue as has the threat of multiplicity of differing local regulations. To promote international harmony, the International Organization of Legal Metrology (OIML) has introduced various recommendations which member states can adopt into their legal structures. The EU was in the forefront of adopting these recommendations and when the United Kingdom left the EU, these rules remained in place. The three recommendations that are of interest to non-automatic weighing devices (i.e. weighing devices that you see at food and vegetable markets, at the deli counter, in the doctor’s surgery, at the Post Office etc) are:

• R 52 – Hexagonal Weights – metrological and technical requirements
• R 76 – Non-automatic weighing instruments
• R 111 – Weights of classes E1, E2, F1, F3, M1, M1-2, M2, M2-3 and M3

Recommendation R 52 – Hexagonal Weights

Recommendation R 52 was the first of these recommendations to be published. It defined the physical sizes of cast-iron weights that are sometimes seen in markets. The recommended sizes are 100 g, 200 g, 500 g, 1 kg, 2 kg, 5 kg, 10 kg, 20 kg and 50 kg. Such weights are made of cast iron and have a hollow in their base. This hollow is partially filled with lead to bring it up to the required weight. Once this is done, the lead plug is stamped by an auditing organisation to certify its weight. The allowable tolerance is ±0.05% apart from the 100 g weight where a tolerance of ±0.1% is allowed.

(Source: https://commons.wikimedia.org/wiki/File:1kg_with_creditcard.JPG)

Typical hexagonal 2 kg weight with a credit card to show its relative size.

(Source: https://commons.wikimedia.org/wiki/File:2kg_auditmark.JPG)

The same 2 kg weight showing the assayer’s mark on the lead plug.

In view of recommendation R 111, there have been moves to deprecate this standard but a counter argument that these weights are easy to manufacture and are often still used in third world markets has prevailed.

Recommendation R 76 – Non-automatic weighing instruments

Recommendation R 76 covers almost all weighing devices that display the weight in question and covers anything between jeweller’s balances and industrial weighbridges.

The OIML originally categorised weighing devices in one of four classes defined by the allowable tolerance of the device, but in recent years have expanded Class III, when it is used for weights above 4 tonnes, has been split into two classes – Class III and Class III L.

All classes must meet the following criteria:

• For a weight to be valid on the device, it must be equal to or exceed the minimum number of divisions with each division usually being equal to one increment.
• The maximum range of the device must be equal to or exceed the value given in the column “Maximum number of divisions.”
• The device must be certified by an accredited certification agency, both when it is new and at regular intervals as specified in the manufacturer’s documentation.
• Other criteria also apply, which are discussed later.

Since the recommendation covers such a wide range of devices the recommendation uses the symbol “e” to represent the minimum increment on the scale. To put this into perspective, consider two different weighing devices that I own. One is a jeweller’s scale which has a capacity of 200 g in 0.01 g increments. The value of “e” for this device is 0.01 g and the maximum value is equivalent to 20 000 times the basic increment. My bathroom scales on the other hand have a different value for “e.” In the range 50 kg to 100 kg, the display is rounded to the nearest 0.2 kg, so on this device, “e” has a value of 0.2 kg thus at 100 kg, the display is 500 times the basic increment.

The classes are defined as follows:

ClassMinimum number of divisions at minimum weightMinimum number of divisions at maximum weightMaximum tolerance at maximum weightApplicationsI50 000Not specifiedNot specifiedHigh precision laboratory workII100 (Note 1) 3 000100 000±0.001%Laboratory work and transactions of high value goods (such as jewellery)III100 (Note 2) 50010 000±0.01%Most commercial and medical transactionsIII L2 000 (Note 3)10 000±0.01%Weighbridges etc (Weights above 4 tonnes)IIII1001 200±0.08%Portable devices used in medical clinics etc

Note 1: e <= 50 mg

Note 2: e <= 2 g

Note 3: e >= 2 kg

Outline definitions of the various classes of weighing devices

The recommendation runs to almost 100 pages as it covers a variety of weighing devices, both analogue and digital including yardarm balances, point of sale weighting devices, medical scales etc. The points that the recommendation covers include:

• Default temperature ranges of operation which varies by class. If the device is designed to operate in extreme heat or extreme cold, the ranges should be catalogued and certification tests planned accordingly.
• If a device has multiple ranges, then each range should be tested separately. For example, my bathroom scale has 0.1 kg increments for weights below 50 kg, 0.2 kg increments for weights between 50 and 100 kg and 0.5 kg increments for weights above 100 kg – this being typical of multiple-range devices.
• The default range of permitted power fluctuations is defined. Operational use must not be affected if the electrical power fluctuates within the specified limits. If the power fails or is outside limit, the device should either turn itself off or display an error message.
• Specification of printouts and displays.
• If the device has a dial and pointer the recommendation defines the spacing of graduation marks.
• The acceptable accuracy of weights used during certification and must be “e/3”.

The above list is a fraction of the criteria that are listed in the recommendation. The interested reader is referred to the recommendation itself.

Recommendation R 111 – Weights of varying classes

Recommendation R 111 covers three principal categories of weights – those used as references for the calibration of other weights, those use for the calibration of weighing devices and those used for everyday purposes in conjunction with a weighing device. The recommendation is limited to weights that are greater than or equal to 1 mg and less than or equal to 5 tonnes.

The standard defines nine classes of weights known as E1, E2, F1, F2, M1, M2, M3, M1-2 and M2-3 (in descending order of accuracy). Three classes of weights are defined for calibration purposes of weighing devices of Classes I, II and III respectively and the remainder are intended either for everyday use for scales of Classes I, II, III, III L and IIII or for calibration purposes of Class IIII devices.

Weights of Class E1 are designed to be calibrated against the national prototype kilogram and to serve as working copies for calibration of other weights. A certificate of traceability against the national prototype accompanies such Class E1 weights. For Class E1 weights of 100 g and above, the permitted tolerance of ±0.5 parts per million. At the other end of the scale, the tolerance weights of class M3 having a nominal weight of 100 g or more is 0.05%. Below 100 g, the tolerance level for all classes of weight is relaxed due to the difficulty of manufacturing of such weights.

Most of the recommendation is devoted to detailed rules concerning the physical construction of the weights, the environment in which they are to be used and the way in which tests are to be carried out. Of note is that the calibration of the weights assume that they will be used in air and that the buoyancy effects need to be considered. The recommendation states that the weight should be accurate when used in air with a density of 1.2 kg/m³ against a target object having a density of 8000 kg/m³. (The density of water is approximately 1000 kg/m³).

Other parts of the recommendation deal with the way in which the calibration is to be recorded, the requirement that the apparatus reaches thermal stability before performing the test and ensuring that magnetic fields are either absent, are negligible or that there is compensation for them.

The interested reader is referred to the recommendation for further details.

(Source: https://commons.wikimedia.org/wiki/File:Weights01.jpg)

Set of weights, range 10 mg – 100 g used for laboratory work.

References:

• R 52 Hexagonal Weights – https://www.oiml.org/en/files/pdf_r/r052-e04.pdf
• R 76 – Non-automatic weighing machines – https://www.oiml.org/en/files/pdf_r/r076-1-e06.pdf
• R 76 explained (plus US Customary extensions): https://adamequipment.com/content/post/what-are-scale-balance-accuracy-classes-divisions/
• R 111 Weights of Various Classes – https://www.oiml.org/en/publications/recommendations/en/files/pdf_r/r111-p-e04.pdf