Multiple conversions for same social distances

If you thought social distancing was simple, think again. Ronnie Cohen draws attention some examples of confusing conversions. When will we learn to think metric and not convert?

I have recently noticed something odd about the imperial conversions given for the two metre social distance signs. I have seen three different conversions in different locations, then I thought if I were familiar with metres and had never heard of the imperial foot, I would be none the wiser. Here are the different conversions I have seen:


Shop Window Sign

NHS Floor Sticker

Shoe Shop Sticker
Different conversions for two metre social distance notices

The first sign gives a conversion of 6 feet, 8% less than 2 metres. The second sign gives a conversion of 6 feet 6 inches, which is by far the closest conversion for two metres and is just 1% smaller. The third sign’s conversion is 22% larger than two metres. This is wildly inaccurate. I saw the latter in a shoe shop in Brent Cross Shopping Centre in London. I also saw the following notice in the same shoe shop:

In fact, a distance of 1.5 metres is equivalent to approximately 5 feet, not 6 feet.

There is a widespread perception that giving conversions is helpful. If different conversions are given for the same lengths, the general public will surely wonder which one is correct. It does not help our understanding of measurements. If the measures are wildly inaccurate, they are unhelpful and misleading. Such conversions are worse than useless. I know that social distancing guidelines are meant to be approximate. If you wanted to give the most precise measurement, you would give a conversion of 6 feet 6 inches but that involves using a combination of feet and inches. If you want to give a conversion to the nearest number of whole feet, you would give a conversion of 7 feet, which is 7% larger than two metres. However, I have not seen that anywhere.

It is encouraging that a lot of social distance signs and posters just use metres. We can avoid all these conversion issues if everyone was consistent and just used metres. Why don’t we just dispense with conversions and just use metres for all social distancing information?

11 thoughts on “Multiple conversions for same social distances”

  1. @Ronnie
    Is there any way to talk to the shop owners and find out what their thinking is behind using signs or stickers with Imperial “conversions” in addition to the distance in meters? Could be enlightening, I would imagine.

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  2. This reader could be forgiven for thinking that after almost half a century of metric education in schools, it would not be necessary to tell anyone what a distance of two metres looks like. But the general public still have to handle imperial units for distance on traffic signs, so are effectively expected to be able to work with both metric and imperial at the same time. It really is time to start thinking about upgrading road signs to show the units that are actually taught, then all these conversions would be a thing of the past.

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  3. metricnow,
    How many traffic signs does the average person encounter daily? So, even if the sign says yards, we know they are really metres? So how many people who see yards just think of them as metres anyway? Even when driving, most people spend most of their driving life going to the same places on a regular basis to where they can go from place to place and completely ignore the signs. I don’t think the signs in miles are as effective as some may think in preventing people from learning metric.
    One pays more attention to distances they they are running/jogging or walking distances for health reasons, and they distances are always metric.

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  4. Daniel, Totally agree with you there. In practice a sign with the word ‘miles’ on is not that common, I see more pedestrian signs in metres ‘m’ and ‘km’.
    It is not the signs themselves that are the problem, it is the spin off from them being perceived as the ‘only’ way to mention long distances, the media revel in it. Either the media needs to change or the road signs, no signs of either changing in my lifetime.

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  5. Daniel:
    I take your point that most/many people drive the same routes all the time, or mostly, and perhaps don’t pay much attention to the road signs. I’m not sure that everyone really thinks yards are metres, though. If that were the case, why aren’t metres allowed on road signs? As far as miles not being an impediment are concerned, I think they are. You learn metres and kilometres, not metres and miles. Metres and kilometres go hand in hand and both would need to be shown on road signs. As you know, I’m sure, all highway engineering is done in metric. The only imperial is the numbers on the (metric-dimensioned) road signs themselves.

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  6. @Ezra

    I have not thought about talking to shop owners about the dual social distance signs. I wonder why so many people think that the conversions are necessary. Government advice on social distancing was given without conversions, using only metres.

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  7. Actually, 2 m is closer to 6 ft 7 in, but the conversion 6 ft 6 in is more than accurate enough. What I find reassuring is that the metric distancing is correct in almost all cases. I suspect that the one in the shoe shop showing the distancing as 1·5 m is of American origin, where the official distancing is 6 ft.
     
    I agree with others; we don’t need conversions to Imperial. And some shop keepers need to go back to school.

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  8. If one were using the “pied metrique”, the equivalence of six feet and two metres would be correct, but the “pied metrique” was only used in France between 1812 and 1840.
    The statement that two metres is about eight feet is correct if we are talking about human feet as opposed to imperial feet! Generally men’s feet are a little over 250 mm while women’s feet are under 250 mm.
    One of the reasons for the metric system was to do away with the different foot lengths. Those who are interested should visit https://en.wikipedia.org/wiki/Foot_(unit) where about 70 different feet are cataloged, ranging from the 272.8 mm foot (voet) used in Utrecht to the 357.2 foot (pied de terre) used in rural Bordeaux.

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  9. When we are talking about conversions I want to bring up a method, viz. dimensional analysis, and especially the factor-label method for converting units. It is touted as being very easy and convenient but I can not see it this way. Here is a Wikipedia article about dimensional analysis: https://en.wikipedia.org/wiki/Dimensional_analysis
    Then I found a video on You Tube for nurses on how to convert units using this method. https://www.youtube.com/watch?v=0N6SmKVWZdI
    The first problem: convert 6 US fl.oz to mL. The fl. oz. is rounded to 30 mL here. To me that is simply multiply 6 by 30, getting 180 mL
    The second problem: how to convert 4000 micrograms to mg. Simply move the decimal point three places to the left.
    Dimensional analysis, however, makes you write everything down in a formula and cancel out units. You can see it for yourself in the video.
    More problems in the video are: convert 5 g to micrograms; 50 mL to US fl. oz; 96 kg to pounds; 20 teaspoons to mL; 2000 mL to litres and 5 L to teaspoons; all solved by dimentional analysis.. Converting 2000 mL to litres using that method is particularly absurd to me.
    This is is not for me and secondly I have always avoided conversions as much as possible. I even think that having to convert metric to metric using dimensional analysis could fan anti-metric sentiments.

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  10. An excerpt from the White Paper on Metrication from 1972 is posted here:
    https://www.reddit.com/r/Metric/comments/q9mz37/a_british_government_white_paper_on_metrication/
    There is a link to download the entire PDF.
    However, what is interesting is that even in the White Paper, the attitude was not clear but wishy-washy. Even in 1972, there was no intent to convert road signs.
    8. The present system for showing speed limits and other road signs is unlikely to be changed for a long time to come.
    107. The most expensive operation within the field of public administration will be the conversion of all road signs showing miles (or mph) to kilometres (or kph). The cost of conversion of all road speed signs is likely to be about £2m and of all road signs indicating distance appreciably more. Unlike the changing of distance signs, where phasing is practicable, the change of speed limit signs must be done as one major operation. 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 (26). The change of speed and distance signs to metric units will need to be considered in detail, but not for some years.
    It is no wonder that metrication is not complete almost 50 years after this paper was published. It was never intended to be. Metrication was intended to fail and I’m sure to every opponent’s surprise the metric system is still here going strong 50 years later, even though the last pre-metric group is trying to bring about a total reversion before they go to the grave.
    A total reversion would have been impossible if road signs had converted. Weather reporting, shop scales, petrol pumps, etc are easy to switch back, in many cases just the flip of a switch or the change of a code, but if the road signs had changed, reversion would have been impossible. But, I feel strongly that there are enough pro-metric forces in the shadows that are going to hold the proverbial carrot in front of their nose and make them think reversion is just around the corner, when in reality everyone will just wait until the old Luddites move on before the metrication is completed.

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  11. To be honest it doesn’t matter if the distance measurements were in Metres then having the conversation into feet, most people who use metres understand them, and those who need conversion into feet are probably closer to being six feet under than six feet distance..

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