Braking

A reasonable length of time ago I started to learn how to teach mathematics the year was 1995/6. During that academic year I received my second placement at a school in Kingston Upon Thames. I was living in Ealing at the time and my first school was The Featherstone High School in Southall and it was a couple of stops away by train. However, to get from Ealing to Kingston was not the easiest of journeys and meant about an hour on public transport. So, I decided to get a motorbike. That teacher training year was a surprise to me for two main reasons:

• I discovered that I really loved teaching and decided to stay in that profession. My plans up to then had been to join the RAF as an educational officer.
• I bought a motorbike, which I consider instant death traps, and I loved it.

So, I took my motorbike test in 1996 I think. I couldn’t remember the braking distances for different speeds and so one of my my flatmates, Greg, came up with the formula:

Using this formula gives you the braking distance in feet when x is in miles per hour. Effectively it splits into two parts; the x is the thinking distance which is roughly one foot for each mile per hour and the x^2 is essentially the kinetic energy factor. I actually used this formula to work out the answer to the question in my motorbike driving test and got it correct although the tester was somewhat surprised I was using feet rather than metres even though both were acceptable in those days.

This distance is an estimate and cars nowadays will be able to stop in much shorter distances. The more you pay for your car the shorter the distance to stop [ish]]. Basically it’s one hundred metres to stop from 70 mph. That’s quite a distance and would probably surprise most people to see it laid out. It’s the length of a running track straight. When I try to visualise distances in the hundreds of metres I visualise a running track opening out to a straight line and then going across the school field. Humans are generally rubbish at estimating distances because it’s not something we do that often. Distance estimation is important in application of fire when shooting and you need to estimate distances quickly using visual clues to make sure you aim at the correct stop to hit the target. Bullets fall down to Earth, accelerating at 1g.

Now we get to the main point of this communication. In my experience over the last two months people are either:

• Stupid
• Unable to estimate distances
• Unable to understand risk
• Unable to follow instructions
• Think they are indestructible

None of those things is mutually exclusive so maybe it’s all of them. My evidence is purely anecdotal and comes from my experiences of going to the supermarket. I have been to work thrice since the UK lockdown started and the few people there have been good at keeping their distances. My place of work is still open to the children of key workers and there have been some in allowing sections of this country to still function. The only other place I have mixed with the public is at the supermarket. I haven’t really ever had food shopping delivered and decided I wouldn’t start now and take a slot from someone else who needed it. Going to the supermarket is something I normally enjoy. I don’t know why but I like seeing the shop. If you think that is strange then I really love supermarkets abroad, I think they are such an insight into the people and I will happily walk up and down every aisle to see what’s there.

My normal supermarket is a Sainsbury’s nearby. In fact I’ve been using them for a while since my Nectar points balance went negative due to their errors. I’m not sure of the economic implications of a negative Nectar balance but I decided to shop there for a while. The first time I went to the supermarket they had set up a queuing system with lines on the floor where people could stand. I am not convinced these lines are two metres apart because two metres is probably further than you think but they are apart and so I’m not going there to measure them. That first time queuing someone was chatting to the person behind me and had to be asked to move away. I mean, I thought the instructions were pretty clear. Two metres is two metres. It’s more than the height of a standard house door. If you stand there with your arms outstretched you shouldn’t be able to tough another person’s hands with their arms outstretched.

Inside the store my experience was mostly positive. People seemed to be mostly keeping their distance. Most aisles are around two metres in width and so if you go down the sides you are probably a good distance away. I did find that some people weren’t following the instructions and while I waited at “pinch points” other people would go between me and the person I was waiting for. This, I think, is mostly to do with people not having patience or any altruism. I tried to do the right thing by keeping my distance but some people weren’t doing their best. This was a little frustrating. Mostly I found the experience OK and I don’t think I was too worried by the other shoppers, by and large it was OK.

A few weeks into the lockdown in the UK I went to a local Tesco store because I needed to buy some clothes. The Tesco has a larger selection of clothing and I honestly didn’t want to go to the Asda at the top of the hill because I was being snobbish. The queuing system outside the Tesco worked well but once inside I found there were problems. Tesco have placed arrows on the floor to try and make their customers move in the same direction and allow more people to browse particular products. That seems perfectly sensible but when a good proportion of the customers decided NOT to follow the one way system – WHICH IS THERE FOR THEIR SAFETY AND HEALTH – then the system fails. I was a good boy and followed the rules in place. That evening I found that a lot of customers either didn’t see the arrows or just ignored them. Too many people passed too close to me. My observances are:

• People wearing face masks and gloves seem more likely to pass close.
• Younger adults don’t give a shit.
• Tesco don’t enforce the system – but how could they?
• Kids don’t know better so that’s fine – don’t take kids shopping unless your situation requires it.

I hated the time I spent in this supermarket. It was frustrating and increased my stress levels to very high. I just wanted to get my stuff and get out. I really don’t understand why people won’t follow guidelines in place to keep them safe. I’m pretty sure they haven’t understood the risk assessment of these activities. Let’s look at these problems I saw:

Face masks and gloves – the evidence is that face masks don’t protect you from the virus. What face masks do is reduce the chance of you passing on the virus if you have it. Now, if you have symptoms you shouldn’t be outside at all. But, you could be asymptomatic, or you could be at the infectious stage just before you get symptoms. Wearing a face mask gives you a false sense of security and so you put yourself into more risky situations. I saw this is Tesco, I saw people wearing rushing around and getting close to people and they were the ones wearing face masks. Gloves won’t do shit. Gloves, again, give you a false sense of security and make it more likely that you will touch stuff. The best thing you can do is wash your hands before you go out and then wash your hands as soon as you get back. Do your best to not touch your face in the times inbetween.

Younger people – they have that sense of invulnerability that I once felt and I get it. They are going to do the things they want to do. But it could be that they are a massive vector for the virus because they are more likely to be asymptomatic. In a recent exercise walk around a lake I saw a group of around twenty youths all together. I understand and no one is really going to be able to tell them what to do.

Tesco decided to implement a one way system. I have spent a while thinking about this and my stress levels at Sainsbury’s are less because they don’t have a one way system. Therefore there isn’t a system for people to follow and so I don’t get annoyed when they don’t follow it. I still get annoyed by people passing too close but there isn’t the added issue of those people also blatantly ignoring the safety arrows of directionality.

I haven’t seen many young kids when I’ve been out and about. I understand that there are family situations that would make it hard for people to leave kids at home and I am sympathetic to them. You can only tell youngsters to do so much. This, of all the transgressions, seems the one that’s OK.

I go to Tesco rarely. This is to minimise my annoyance at people not following the system. I don’t wear a mask and I don’t wear gloves. In my head I model the water suspended droplets flowing around people as they move around and I try to avoid those areas. I hold my breath at certain times and I try to minimise the risk to myself. I don’t know if I’ve had the disease and I don’t know if I would be immune. I hope I have had it. I would like to be in the position to know that I don’t have to worry about getting it. I would like to be able to do my work and help others knowing it is unlikely I can pass it on and also unlikely I can catch it again. These are all things I do not know. The most important thing for people to do now is to reduce their own risk of getting the disease or passing it on. Until there is a vaccine available everyone is likely to get this at some point. Everyone is going to get ill and there are going to me many more deaths. What we need to do is minimise the risks to all and keep the health services going by spreading out the infection rate.

A couple more things to mention; the virus is called SARS-CoV-2, that’s the official name, the disease you get from the virus is called COVID-19. The virus belongs to the common cold virus family and not the flu virus family – they are very different shapes. The R value that the media are going on about is really the R₀ value. That’s pronounced R Nought or R Zero. I think the media have been a little lazy on this one but that could be just me. There are other R values and it’s important to talk about the one you mean. This one is the only one being talked about in the media so maybe I should be softer on this issue.