A Driving Instructor's Blog

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Note: As of 17 October 2019 – it’s Autumn, people. Yellow leaves is normal!

Our Silver Birch in June 2017I originally wrote this article back in 2014. At that time, our tree began to produce a lot of yellow leaves in mid-June, and after a lot of research I managed to figure out the cause and remedy – and that’s what this article was originally about.

However, 2018 was the hottest year on record. The heat lasted for months, and it introduced another problem (which may or may not have been a factor back in 2014 without me realising it) that affected pretty much every tree in the country. Heat stress.

The article becomes popular each year, but things kicked off much earlier in the season in 2019. I suspect that this was down to a combination of the mild end to a dry Winter, which jump-started Spring, and the lingering effects of the 2018 drought.

Yet another problem in 2019, possibly another knock-on effect from the previous summer and mild winter, was green fly. In Spring and early Summer they were merrily chowing down on the new leaves on my tree. I bought some Ladybird larvae and released them into the canopy, and they seemed to do the trick.

To summarise everything I have discovered about premature yellowing and leaf drop in Silver Birches over the last few years, it can occur for the following reasons:

  • nutrient deficiency
  • iron deficiency
  • lack of water and heat stress
  • manganese deficiency

And I now know that it’s easy to get all of them at once (note that manganese deficiency is something I found out about recently and have been experimenting with during 2019).

When the yellowing first occurred back in 2014, we were worried. Googling for an answer was next to useless, since most of the technical advice was North American, focusing on the Bronze Birch Borer (a beetle that feeds on white birches), or the perils of trying to grow trees in either a desert or a swamp. And that was only from the experts – the general public was quite prepared to believe that it was an alien conspiracy, and was more than prepared to defend that view. Our trees had none of the beetle infestation symptoms other than leaf drop, and although the British never shut up about the bloody weather, we were not growing ours in anything other than normally-drained British garden soil.

After a lot of research, and after sifting out the utter crap, I discovered that yellowing/leaf drop is usually caused by deficiencies of nutrients and/or iron in the soil. In 2018, with the hot summer to contend with, I further discovered that lack of moisture and/or high temperatures can produce the same symptoms – it’s called heat stress, and I’ll discuss it later (I wrote a separate article about it in August 2018).

Note that the problems described are not confined to Silver Birches. All trees and plants can be affected by nutrient deficiencies or heat stress, though you may need a different fertiliser to address the nutrient issues.

The problem we had in 2014 was characterised by bright, canary yellow leaves – just like in the Autumn, though not as widespread throughout the canopy – which began falling off the tree. I can’t honestly remember where I found this now, but somewhere in the hundreds and hundreds of forum pages and obscure “ask the expert” sites rattling on about the bloody Birch Borer I came across a single one-line comment mentioning two easily-applied ideas that made absolute sense, and which could be implemented without calling in David Attenborough and Rentokil. Fertiliser and Iron Treatments

Nitrogen (nutrient) deficiency is resolved using ericaceous fertiliser (for lime-hating plants, which is what birch trees are). It is available from various manufacturers, such as Miracle-Gro, and can be bought from most decent garden centres and from many online retailers (including eBay and Amazon, where I usually get mine). It only costs about £5 for a box of the granules (you often get multi-pack deals), and there’s enough in one box to manage a small-medium sized tree for at least half a season (note that for larger trees, you might have to use a lot more of it). You can also get liquid varieties, which I’ve switched to since 2018 because of my new irrigator toy; and slow-release granules, which work for up to three months, and which are great for those treating small areas (I use them in my containers of Blueberries).

Normal fertiliser is no good for birches – it has to be the ericaceous stuff – and you just dissolve it in water and spread it around the tree. The slow-release granules are just sprinkled on the ground and watered in (I just wish they’d make the damned things in camouflage green, instead of the “hey, look at me all over the lawn” multicoloured mix they actually are).

Leaves suffering from chlorosisLeaves that look like those in the images here are suffering from iron deficiencyknown as chlorosis.

Leaves are green because they contain chlorophyll. Simplifying the subject, chlorophyll allows plants to convert light energy into sugars they can use via the process called photosynthesis. Chlorophyll is green – hence the colour leaves usually are – and it contains iron, so if there isn’t enough iron you get less chlorophyll (hence the yellow colour). The plants compensate for the subsequent lack of food by shedding leaves and going towards a shutdown state. That’s what you can see here.

Chlorosis is resolved using sequestered (or chelated) iron, such as Maxicrop, shown above. It’s a seaweed extract, so perfectly natural, and it comes as a liquid. You can mix it in with your fertiliser and water it in at the same time. I’ve recently discovered a source of Maxicrop in commercial 10L containers, which is more cost-effective than buying it in 1L bottles. It stains like hell, so be careful not to drop the concentrated liquid on pathways and decking.

Close-up of leaves suffering from chlorosisAnother symptom of soil nutrient deficiency is that new leaves may be small and misshapen, instead of the classic Birch leaf shape. Some of ours were like that in that first season.

Back in 2014, after a single application of fertiliser treatment, leaf drop stopped almost immediately once the already-dead leaves had fallen. The tree even threw out some catkins, which had been absent up until then. In subsequent years, I started feeding every few weeks from March with both fertiliser and iron and we had no leaf drop at all until 2018. In May 2017 our tree looked like the photo at the top of this article, and here’s a close-up of the leaves from that year. Does that look healthy, or what?

Close-up of our tree's leaves in June 2017An additional iron treatment for the longer term is to water-in iron (ferrous) sulphate periodically. This replaces iron in the soil, too, but it also acidifies the ground over time, which is beneficial for ericaceous plants. It’s also very good for your lawn – iron sulphate is a moss-killer and a grass-greener (it’s sold for these purposes, and I use it several times a year to kill moss in the lawn).

Why does nutrient deficiency occur? Well, bear in mind that when trees and plants die back in winter in the wild, the leaves they shed decompose and return nutrients to the soil as they do so. In urban gardens, though, leaves are usually swept up and taken to the tip to keep the garden looking tidy. That means the soil becomes depleted of those nutrients over time and you get problems like this. It’s fairly obvious looking at it now, but I was like everyone else in thinking that when you planted a tree you just forgot about it and let it grow. It turns out you need to look after them almost as much as you would a tomato plant or an ornamental cactus.

You have to keep the treatments going at least once a month between March and September, and you have to follow the same routine each year (or at least over alternate years). If you don’t, the problem will come back at some point.

Now we come to the extremely hot summer of 2018. Around the end of June, I once again noticed a few sprays of yellow appearing. I briefly wondered what was going on, but I guessed right away it might be linked to the prolonged high temperatures and low rainfall we’d experienced up until then. After Googling it I concluded my tree was, indeed, suffering from heat stress. The solution to this is to get water down to the roots – it’s called deep watering – but that’s easier said than done.

One way of doing it is to use deep watering spikes. These are tapered tubes that are hammered into the ground around the tree, and into which water is fed slowly so that it gets to the roots deep down. I didn’t have time for that in 2018 (with the ground as dry as it was, it’d have been like trying to hammer a nail into plate steel), so I went for the longer-term sprinkler method. Every night, I set the sprinkler going and watered for a couple of hours in each of several zones to ensure even saturation (we didn’t have any hosepipe restrictions, and I wouldn’t have continued if we had). This allowed water to seep down deep into the soil, and it fixed the problem in less than a week (it also turned a completely brown lawn into a lush green carpet).

With hindsight, all trees in 2018 had much thinner canopies than usual – as I mentioned earlier, heat stress isn’t just confined to birches. The leaves on my own trees were smaller than they were in previous years, but about a week after starting deep watering the birch produced some new shoots and the leaves that appeared were much larger. And some very fat catkins also appeared.

As a result of the heat stress problem, and still needing to keep the other treatments going, I have now invested in a combined watering/fertilising system, which I have written about separately. I can highly recommend that device – the Access Irrigation Static Dilutor.

I’m updating this in late August 2019, and our birch has been fine and is still completely green.

Can you rescue leaves which have turned yellow?

No, probably not. The important thing is that by feeding and watering the tree you can stop any further yellowing – and believe me, the first time you do it the effects will be quite noticeable within a short time.

I would imagine that chlorosis could be reversed if it is caught early, since pale leaves are not necessarily dead – they’re just iron-deficient. In that case, you might be able to save some partially-yellowed leaves by applying the chelated iron treatment. As an example, in early June 2018 (before the heatwave really kicked in) I noticed my neighbour’s usually-dark green Cherry Tree leaves were very pale and many yellow ones were falling. I told her about the iron treatment and she bought a bottle. The leaves on that tree turned dark green within a few days and no more yellow ones were produced.

Do you have to keep treating the trees?

Yes. If you don’t, the problem just comes back once the tree has used up what you’ve fed it, especially if you bin the leaves again the following autumn. Huge trees will suck up all the nutrients and water, and if you’re raking up and binning the leaves each year (or if the soil is dry and there are no prolonged periods of rain) nothing gets returned to the soil.

Treat your trees from March until September. Feed at least once a month (even two to three times during the earlier months) – and water regularly in hot weather anyway, as they do need moisture.

How often should you feed?

I do it once or twice a month.

Can heat and drought cause them to lose leaves?

Yes. If they are stressed you may get them dropping leaves, and if not treated the leaves can even go brown and die on the tree (I saw a lot of Silver Birch trees on road verges like that in 2018). It’s a good idea to water them deeply during hot, dry periods. Once or twice a week should be enough, though more frequently won’t hurt if the dry period is prolonged.

As I explained above, the hot weather we experienced in summer 2018 caused my tree to produce some sprays of yellow leaves. I commenced deep-watering from June, as well as feeding regularly. This was the first time heat/drought had been an obvious problem, so it caught me out a little. However, after a week of deep-watering leaf-yellowing stopped completely, and the tree was healthy throughout the rest of the heatwave (as was the lawn, which was parched brown, but ended up lush green).

Remember that after a period of drought (or prolonged dry weather) it needs an extended period of rain to wet the soil again, especially deep down. A few heavy downpours won’t do it, and you will still need to help things along.

Will a Birch recover from drought?

It depends on whether the drought killed it or not. A reader wrote to me in 2018, mentioning that his tree had lost its leaves, and I advised that the only thing he could do right then was to feed and water – and hope for the best. He wrote to me in 2019 to tell me the tree had started to rock in the wind, and that a tree surgeon had subsequently declared it dead, and had had to remove it. Apparently, the roots were rotten.

There’s no way of knowing if it was just the drought that did the damage. The tree may have been weakened by not feeding and watering over previous years, and the drought was just the final nail in the coffin. But the 2018 heatwave certainly caused problems.

Birches were showing profuse growth of leaves and catkins (mine was) as early as mid-April in 2019. If yours is still struggling, then it doesn’t look good. The 2018 heatwave did a lot of damage, and since not many people do the feeding ritual that I have covered in this article, trees may already have been struggling. That said, mine has certainly recovered, although I did catch on very early and stopped it becoming a major issue.

All I can say is: water (if it’s not raining much) and feed.

Is there any other way to deal with the problem?

You have to get nutrients and iron back into the soil. And you need water in order for the roots to be able to access those nutrients. Yes, you could use your own mulch or bought compost, but obviously this is not so attractive in a normal garden (removing it is what got you here in the first place). It would also take longer to have an effect. But it would still work, given time.

When do Birch trees normally start to shed their leaves?

The short – and very obvious – answer is: in the Autumn. It can vary a little up and down the country (just as Spring tends to start earlier the further south you are), but in the Midlands they usually start to show sprays of yellow from late September to early October. It often seems triggered by a noticeable drop in night time temperatures. The leaves will begin to fall from that point – very lightly at first, then increasing as the yellowing spreads.

Why do birch trees drop leaves so early?

They don’t. They drop them in Autumn, like all other trees which shed their leaves each year. If yours is turning early, you may have a problem – probably one which can easily be sorted by reading through this article.

How do you apply these treatments?

You make up the required solution as directed on the pack, then water it into the area specified. I have now invested in a combined watering/fertilising system, which I have written about separately. However, you can use a watering can and hosepipe/sprinkler as necessary. Note that if the ground is dry, a watering can won’t get the nutrients down to the roots, so a heavy watering is essential.

I do this up to twice a month between March and September. In 2018, I was deep watering every night during the heatwave.

How much should I use?

Like I said, the mix ratio is on the pack. Make sure you scale things up, though. The pack might well say use a capful or a spoonful in 4.5L of water, but this is for a small area of border and the plants therein. If you’re feeding a large tree, it may well be that you need to use a half a pack of the stuff dissolved and spread over 100m².

Why are fallen leaves sticky?

You’ve got greenfly! Specifically, the birch aphid, Euceraphis betulae. They feed on the European Birch, Betula pendula, and they increase in number during warm and dry weather – which is what we have right now (and did have for most of the winter). Aphids secrete honeydew as they feed, and that’s the sticky stuff you’re seeing. Apparently, you can get different species of greenfly that feed on specific trees.

Someone found the blog on this search term in late May 2019. Right now, my tree is very healthy, and is putting out a lot of new growth – but I have noticed something is eating the young leaves. When I looked closer, I saw a lot of greenfly. You will also get a few leaves falling with this problem.

You can kill them with a soap/water mixture, though no one has ever been able to tell me precisely how you apply that to a 20 metre high tree. And the same goes for any chemical method relying on direct contact.

An alternative solution is to introduce predatory insects – something that eats aphids. The best one is the Ladybird, and you can buy them online. There are other predatory insects you can buy, too.

My tree is losing branches and twigs

If the tree is weak then it is understandable that twigs and small branches might fall off. Once they’re stronger this will stop. In any case, if it is windy, a few dead twigs are bound to fall off. It’s just nature.

Early in the year, another likely problem is crows (the winged variety). From March (February in 2019) they will be nest-building, and they are very, very selective in their choice of twigs for the purpose. We get them nesting near us, and they will tear off a hundred twigs and drop them until they get the one they want. It’s nature, so we don’t worry.

Why do Silver Birches drop so many twigs?

As I said above: crows (and similar birds). As of February/March 2019 they were actively nest building (it’s usually March, but the warm end to winter has kicked them off early).

They will carefully select the twig they want, but the sods will tear off loads more before they find it. I watched one on a dead Birch tree when I dropped a pupil off after a lesson, and he (or she) had broken off a huge twig – almost a branch – and was trying to get into a position to fly out of the branches with it.

Also note that high winds might knock a few loose twigs down.

When do birches start to show leaves?

In spring, obviously, but the precise date varies depending on both the tree and the weather. In 2019, they were about a month earlier than 2018 in the UK.

Someone found the blog in mid-April 2019 on this search term, and I suspect it is because their own tree hadn’t yet shown any leaves. I refer again to the hot summer of 2018, and the effects of heat stress. I’m sure that many trees – not just birches – were killed by the drought, but people wouldn’t realise until the following Spring. In 2019, my own tree was in almost full leaf by mid-April, and certainly by May, with lots of catkins.

My tree is taking a long time to show any leaves

I’m not an expert, but if this happened to me – and knowing what I know now – I’d start feeding it pronto. Of course, it might just be slow – some trees do seem to lag behind others – but a good feed can’t do any harm. Mine was in full leaf by May 2019, whereas neighbours’ trees were still in the process of producing leaves. In hindsight, and following my observations throughout the year, the heatwave seemed to have stressed trees to the extent that their canopies were sparser than usual (leaves were smaller), and this may have been what you were experiencing.

In the worst case, your tree might not be in good condition at all, but you’d have to call the experts in for that.

I’ve got catkins but no leaves

Someone found the site in April 2018 with that query. You’ll probably find that in a couple of weeks you’ll have lots of leaves. As I have said in this article, I start feeding mine from March onwards. Leaves start sprouting a week or two earlier than my neighbours’ trees, and the foliage on mine is usually much denser. The catkins often come before the leaves.

I strongly recommend feeding them regularly as a matter of course – and watering if the ground is dry.

Are the leaves changing early this year?

This was a generic search term used to find the blog in mid-July 2017. The short answer is no, they are not – not in July, anyway.

In hot and dry weather, many trees can become “distressed” and start to shed leaves. Silver birches are affected by this. Also, greenfly infestations can cause leaves to die and fall. If a lot of leaves are turning yellow on the tree then you have a problem – quite possibly one of those which are the main subject of this article. However, a few leaves falling is probably nothing much to worry about.

Do Weeping Silver Birches lose their leaves in Autumn?

Yes.

When do Silver Birch leaves go all brown?

They don’t. The leaves should go yellow and fall off in the autumn.

I had quite a few visitors from this search term in 2018, and when I looked it up it seems that extreme cases of chlorosis and heat stress can result in leaves turning brown (see this supplementary article). It could also be a disease or infestation which you could treat, but the tree itself might also be dead – especially if it has been having any of the problems I mentioned above over previous years. Best to call in the experts.

Could the 2018 heatwave still cause problems in 2019?

It’s possible. Remember that we’ve had a relatively dry winter, too, so there may not be much moisture for the trees to draw upon. If they were weakened by the hot weather in 2018, and there’s still not much moisture in the ground come Spring, it could mean that they are still struggling at a time when they really need a lot of energy to put out new growth.

The hot summer of 2018 almost certainly killed off a few trees, so it is safe to assume it must have stressed the hell out of many others. That was why many started shedding leaves early – they were going into shutdown to protect themselves.

My tree is doing fine, because I water and feed it regularly. So there’s a clue to what you need to do.

Does this advice only apply to Silver Birch trees?

No. Chlorosis can affect many plants, and lack of nutrients is going to be a universal issue. You might need a different fertiliser to address any nutrient problem, but iron will likely fix chlorosis. Lack of water can kill virtually any plant.

Recently, someone found the blog as a result of premature leaf drop in their Betula utilis. This is the Himalayan Birch, famed for its peeling paper-like bark, and it is a member of the same family as the Silver Birch. In the Himalayas, it often grows among Rhododendron plants (look at that fertiliser again – are you seeing the connection, here?), so the advice given above would work for the Himalayan Birch, too. And it also worked for my neighbour’s Cherry Tree, as I mentioned earlier.

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I wrote this back in 2012, but someone contacted me about it so I’ve updated it.


At the time I wrote the original article, a debate was raging on one of the forums concerning reference points – using parts of the car to reference your position in relation to other objects, like the kerb.Slide Rule

Some instructors insist on putting little sticky dots or other marks all over the car. Indeed, when I did my Part 3 exam I rented a car from another instructor, and his was festooned with the things. Red ones, yellow ones, blue ones. They were everywhere. It was like sitting inside a psychedelic three-dimensional slide rule.

The problem with this method – and it IS a huge problem which those who use it are usually ignorant of – is that everyone sits in a different place in the car. A short person sits a long way forward, and a tall person sits a long way back. Everyone else is somewhere in between. And any given pupil might easily be in a different position on each lesson because of how the rake of the seat is set. So a sticky dot which lines up with, say, the kerb for a short driver is going to be miles off the mark for a taller one – and it might not work on the next lesson if they’ve got the seat adjusted differently. The sticky dot only works for one size of person under a specific set of conditions.

To make matters worse, if you point out a sticky dot to someone and ask them where the kerb is in relation to it, the first thing they usually do is start moving their head around. It’s just the same when you are teaching them to adjust the mirrors – you tell them to adjust the rear view mirror so they can see the back window – and they lean over. Or, you say to them “sit normally”, and they immediately adopt the most UN-normal pose they can think of.

But just as ignorant are those instructors who pooh-pooh reference points entirely, and insist they never use them. Hopefully, they just mean that they don’t use sticky dots, because it is a basic animal instinct to use some sort of position-based reference to avoid walking into walls or falling out of trees.

This is exactly what a pupil has to learn when you’re doing, say, a reverse into  a parking bay. Whatever method you use for that, the pupil has to be able to determine where they are in relation to the bay and make corrections as necessary. If you stop the car for them and ask them to look at the lines (in the mirror or through the door windows), there is a reference point there waiting to be discovered. Some will find it, others need a bit of extra assistance, and you might ask them to position the car so that the line lines up with, say, the door handle inside, or perhaps the window button. Wherever it is, that reference is likely to be different for each pupil. It cannot be covered by a sticky dot that works for everyone.

Much of the problem stems from the fact that instructors seem to have purchased Coaching For Dummies, but have only got as far as the table of contents. They think that all an ADI has to do is sit in the car and ask questions, and the pupil will learn how to drive by themselves. The sticky dots come about as a result of those learners (the majority, in fact) needing more guidance, but the instructor not knowing what to do.

What are the reference points for ADIs and instructors?

Someone found the blog on precisely that term! Quite simply, there aren’t any universal reference points! They’re different for everyone, and for every car, and if you get bogged down with fixed points you run the risk of becoming a very bad instructor.

As an example, if you’re doing the reverse bay park with a pupil and you want them to be able to position the car relative to the target bay somehow (depending on your method), stop the car when YOU know it’s in the right place and ask them “where is the line?” Get them to relate it to the mirror or the inside door handle or something. Now they have their own way of referencing the car’s position relative to the kerb. If they need more help, tell them what they need to look for, and get them to perfect the positioning.

Should you use sticky dots or tape on your Part 3?

If you do, be careful. When the Part 3 involved role play, I know that some examiners went to town tying the candidate in knots with this way of teaching. It was easy for them to do that because of the drawbacks I mentioned above.

I don’t know how they’d view it now, but you need to make damned sure that whatever you are doing works reliably – and sticky dots often don’t.

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Asda Cashback Plus credit cardI’ve never used a fuel card, and for a good reason. I’ve been approached many times over the years (damned Yellow Pages) by companies offering me one, but the simple fact is that I have never been convinced that any savings are great enough, real enough, or reliable enough. Not for me, at any rate.

You see, when you look at what fuel card providers say, it’s always something like “save an average of 3p per litre against the national average forecourt price”. It’s that bit in bold which is the fly in the ointment. Fuel in Nottingham is – as long as you stay away from city centre garages – well below the national average in terms of cost per litre. At the time of writing, a litre of diesel costs me 125p, and yet the national average is apparently 132p. I would only ever “save” money if I sought out one of the joker garages around this way who charge this much, which would be stupid if I can already buy it at full price elsewhere for 7p less.

But what if there was a way to get a discount even on the lowest fuel prices? Well, there is – and it works all the time, no matter what the advertised price on the forecourt is, and it works anywhere.

I shop regularly in Asda, and my average weekly spend on groceries there is around £150. I also buy my fuel from Asda (it is the same quality as the equivalent basic grade from anywhere else), and my average spend on that is also around £150. A total of £300.

A few years ago, I came across Asda’s Cashback Credit Card Plus. It offered 2% cashback on virtually all purchases from Asda – crucially, including fuel. And although I had once vowed never to have another credit card as long as I lived, I was now in a position to be able to pay off an entire credit card bill each month without blinking, and since it would actually save me money I decided to try it. It works like this.

My weekly fuel spend attracts a cashback figure of £3. The quantity of fuel involved is about 120 litres at 125p per litre, so that equates to a discount of 2.5p per litre. But since I also spend the same amount on groceries, I get another £3 cashback with that, which means another 2.5p discount if I apply it to my fuel (whichever way you look at it, it’s money in my pocket). It equates to a saving of about £300 a year.

Cashback is redeemed by way of a voucher. Each time you use your card, cashback is added to your account, and when you’re ready you just choose an amount from your cashback balance and print off a voucher. You can’t use the voucher to pay for fuel directly, but since I already shop in Asda I just use it there. Obviously, you have to factor it in appropriately when you complete your tax return, but that doesn’t stop it being a saving on fuel costs.

Although the 2% cashback is only on Asda purchases, you also get 0.2% cashback on all other purchases made using your card. I know that 0.2% might not seem much, but buying a TV or something similarly expensive attracts up to another £5, and another 5p per litre discount for a week. As long as you clear your account each month, there’s no interest. Basically, the more you use your credit card for, the more cashback you get.

Unfortunately, the Cashback Plus card is not currently available to new applicants (since June 2019), but there is still the basic Asda credit card, which gives 1% cashback (and 0.2% on non-Asda purchases). This is still better than most cashback (and fuel card) deals out there right now if you are in an area which has below average fuel prices.

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Hatice Sadir - a normal (but dishonest) womanThere was a story in the media recently about someone who attempted to cheat on the theory test by having a bluetooth device under a headscarf.

As usual, ADIs across the web forums and social media know more about the story than anyone else – even though they only just read it in the newspapers – and it has prompted the usual “ban the burkha” mob to mount their soapboxes once again now that Brexit has given them the necessary bravado.

The woman in question, Hatice Sadir, was Turkish. She spoke very little English, and had failed a test a few weeks previously. It appears that she paid someone £300 for a two-way bluetooth device including specially designed headscarf. She booked a test with voiceover through headphones, and this was therefore audible to whoever was on the other end of her two-way link, and they told her the answers as the questions were read out.

Test centre staff recognised her from her previous visit. They noted that she hadn’t worn a headscarf the first time and were suspicious at that, and the fact she finished the test very quickly – which they found unusual for someone with language difficulties.

You will note from the photograph of Sadir, apparently outside the court, that she appears very westernised. She has a tattoo on her arm in the fashionable mode. The fact that she is (probably) Muslim is irrelevant. However, in their versions of the story, The Sun and the Daily Mail have identified the “headscarf” as a “hijab”, as is their modus operandi these days.

Sadir, a mother of three, was just a very stupid woman who was desperate to get a licence. Her (probable) religion has nothing to do with it. The only thing I find annoying is that she got a suspended 20 month prison sentence, when she refused to identify whoever it was who was providing the service she paid for. It ought to have been 20 months in custody just for that.

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Flip-flops - the most inappropriate driving shoesWith the weather we’ve had recently, there’s a good chance you’ll have had pupils turn up half naked for their lessons ready to sweat all over your seats (one of mine has been bringing a towel to sit on after I ribbed him about wetting the seat). Then, five minutes later, they’re moaning about being too cold because you have the aircon turned on (assuming you’re not a tight-arse who refuses to use it).

One issue which comes up regularly throughout the year, though, is what they have on their feet.

At the most basic level, a new driver has got to learn how to control the pedals, and especially the clutch. To do that, they’ve got to be able to feel it – which they can’t if they’re wearing big, clunky shoes. Running shoes are probably the worst for this, because they’re specifically designed to absorb shock (and therefore any light touch on the pedals), but any kind of shoe with a platform is going to make clutch control harder. This is especially true if the pupil hasn’t driven before, and even more so if they’re one of the types who is going to have problems in this area anyway.

I had a pupil a few years ago who was one of the jumpy kind. One day I picked her up directly from work, which meant she had ‘forgotten’ her driving shoes. She was wearing platformed Doc Martens – literally, with a four inch chunky heel and bulldozer tread underneath. I abandoned the lesson after less than ten minutes before someone was killed, and drove her home. In a similar vein, I remember once seeing a woman get out of a Mini Cooper wearing massive goth boots with wedge soles that were at least three inches thick (below the knee, she was a ringer for Karloff’s Frankenstein). You cannot drive safely in those. Period.

I always advise pupils to wear flat soled shoes with a thin profile. Anything thick is going to make life difficult, and it drives me crazy when one turns up for their very first lesson in designer running shoes, with the extra thick sole and a concealed wedge heel.

Speaking personally, I absolutely hate it when they want to drive barefoot. My reasoning behind this is that I know from direct experience that you can stub your toe or even cut your foot on the pedals if you hit them in the wrong place at the wrong time, and it bloody hurts. Car manufacturers don’t seem to put much effort into ensuring the undersides of the pedals free from burrs or sharp edges. Furthermore, there is no way most people can brake as hard barefoot as they could in shoes. And if it’s more than half an hour since the car was last valeted, the floor mat will have grit on it, and the last thing you want is to have to execute an emergency stop in your bare feet only to discover something sharp stuck on your sole.

Having said that, I had one pass recently who drove barefoot. I let her do it (after telling her off the first time for trying to stow her shoes in the footwell) after I’d done my usual test in this situation: the Emergency Stop. If they can execute an Emergency Stop barefoot to the standard I expect, then they can drive like that if they want (though I still don’t like it). And she could. However, at the same time she had referred a friend to me who was in the same Halls of Residence, and she couldn’t. One day a few months ago, she came out to a lesson wearing huge furry slip-on slippers (‘why’ was a long story which I’m not sure I fully understand even now). She immediately knew they were not good for driving and asked if she could drive barefoot.

I said that I didn’t mind (because her friend did it), but I was concerned about how well she would be able to operate the brake in bare feet. I asked her to brake firmly while we were stationary and to tell me how it felt. She said it hurt, and she didn’t think she’d be able to brake hard if she needed to on the lesson. Problem solved, and we rescheduled – with the additional light-hearted warning not to come out with the wrong shoes again.

I can think of loads of examples where pupils had previously worn sensible shoes, then come to lessons wearing different though not necessarily inappropriate ones, and had a stinker – just because the shoes are different! Small differences can have a huge effect on some people.

Pupils with larger feet also need to be careful. Anything much above size 9 or 10 doesn’t work well if their shoes have long toe caps, because they’re likely to start catching on the cowling above the pedals. Winkle pickers are a no-no if you have large feet in many normal cars, and since they often have absolutely no grip (just a thin, shiny sole), the risk of the wearer’s foot slipping is also greater.

Very wide- and loose-fitting shoes – Ugg boots spring to mind – are also potentially dangerous, because if you try to slam on the brakes there’s a good chance you’ll make contact with the brake and gas pedals at the same time. And it does happen – it happens sometimes even with small-footed people wearing sensible shoes, so throwing Uggs into the mix is just asking for trouble. The same is true when someone insists on wearing some sort of hobnailed boot two sizes too big as a fashion statement – they’re too bloody wide.

Probably the most dangerous shoes for driving, though, are backless types. Mules, backless sandals, and flip-flops. It’s not necessarily anything to do with the heel thickness – though it can be if they’re platformed – but the fact that they can slip off. I mean, think about it. You can potter about as much as you like in summer wearing flip-flops or mules, but try to run and it’s 50-50 whether they will stay on, and 50-50 whether you end up flat on your face on the pavement or road. They present the same risks in the car if you have to move your foot suddenly to brake – with the additional chance that they will fall under the pedal and prevent you from depressing it fully. They could even get tangled up sufficiently to prevent you being able to brake at all. And don’t dismiss that out of hand – I once had a loop in a shoe lace double bow get itself completely over the clutch pedal (God knows how) so I couldn’t take my foot away or lift it high enough to declutch, and when I slipped the shoe off it swung under the pedal and stopped me declutching fully anyway. Shit happens, as the saying goes.

Strap-on sandals are not so bad, though the open toe arrangement still means you can catch your foot more easily if the sandals are particularly large and oversized (which many are these days).

And it goes without saying that trying to drive in high heels is just plain stupid. The heel messes up how you have to operate the pedals, and you cannot get anything like the same force if you really needed it. Many high heels have shiny soles with little grip, which makes matters even worse.

It isn’t illegal to drive barefoot, nor are any specific types of footwear banned or even mentioned in the Highway Code. The only reference is in Rule 97 (partial quote):

Before setting off. You should ensure that

  • clothing and footwear do not prevent you using the controls in the correct manner

However, DVSA has been quoted separately as follows:

Wear sensible clothing for driving, especially on a long journey. Suitable shoes are particularly important. We also would not recommend driving barefoot because you don’t have the same braking force with bare feet as you do with shoes.

My comments above are based purely on my own experience and knowledge, and they agree completely with this DVSA advice. And so do various other organisations.

I wear flip-flops and never had a problem

This stupid argument makes me angry – especially when it is coming from ADIs.

Everyone knows that if you have a set of expensive crystal glass goblets you shouldn’t drop them. If you do, they’re likely to smash. However, someone somewhere will undoubtedly have dropped one by accident one time, and it will have bounced on the carpet or the arm of a chair, and survived. This does not mean it is OK to drop or mishandle delicate glass goblets. It just means you were bloody lucky.

As I said above, if you try and run in flip-flops or mules, they’re easily likely to come off or send you sprawling (possibly both). The chances of that happening are roughly the same as they are of you getting away with it. If personal injury is one of the possible outcomes, then those odds are not good. If death for you or a passer-by were a possible outcome, they’re catastrophically bad.

I drive in high heels and don’t have a problem

There is no way you can drive as safely in high heels as you can with sensible flat soles. Period. It is a simple scientific fact based on the change to the way you have to apply leverage to the pedals when a high heel is extending and deforming your foot length. Having to brake hard in an emergency situation is going to be a lottery if there is the chance of your four inch heel making contact with the floor before you’ve got the brake on hard enough, or if it snags on the mat.

Remember the example I gave above, of the woman in the goth boots? Three inches of plastic increasing her leg length by 10% and suppressing all feeling of the pedals? Driving in high heels is no different – possibly worse – and anyone who suggests otherwise is a complete idiot, even if they have “always done it”. That’s the risk you’re takin each time you drive in heels.

Pupils will drive in those shoes when they pass

That’s their problem. Your job is to try and educate them in what’s right and what’s stupid while they are with you – not to encourage them in dangerous practices.

I advise all of mine to keep a pair of driving shoes in the car when they pass and not to risk it with heels. Beyond that, it’s up to them.

It’s not against the Law to wear flip-flops

Well, you’d probably still be arguing the toss even if it was. But the fact that it isn’t specifically against the Law doesn’t mean it is the sensible or right thing to do. That it isn’t specifically against the Law means that you doing it is your problem as you struggle with simple common sense. But if you’re encouraging others to do it, then you have become the problem.

But you let people drive barefoot

And I don’t like it. I only give in if they can prove to me that they can do an Emergency Stop properly. As it is, I can count on the fingers of one hand the number who have done it out of many hundreds I have taught. Quite frankly, I wish they would make it illegal to drive barefoot or in inappropriate shoes.

What shoes do your wear?

Deck shoes. I suggest to my male pupils they drive in something similar if they have any issues on lessons. I suggest to the females that ballet pumps with a firm sole are worth a try.

Why shouldn’t you put your shoes or bag in the footwell?

If you brake, whatever is down there will move forward. The only place for it to go is under the pedals. So if a kid on a bike rides out in front of you and your bag has moved under the brake or clutch, one of you will be in hospital (or worse) and the other will be up on a careless driving charge (or worse) and about 99% of the way towards becoming an ex-ADI.

Putting your shoes or bag in the footwell isn’t a problem

I have a tidy bag on the back seat of my car for a good reason. On more than one occasion during my driving lifetime, sharp braking has resulted in a bottle or book sliding under the seat and straight under the pedals. The design of the car footwell and the universal laws of physics guarantee that loose objects will end up there if you brake hard. Shit happens.

Storing anything in the footwell is dangerous. I regularly get people wanting to put their shoes, handbags, and even an umbrella down there. I simply won’t let them. Because I know from experience how dangerous it is.

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Another mass shooting in the USA. And just when you think that, this time, someone must start to take gun control seriously over there, you see this:

Texas Attorney General Ken Paxton, however, said gun control would probably not have stopped the attack.

He added that if a “crazy” gunman launches such an attack, there is no way that law enforcement officers could be there to stop it.

“The best way is to be prepared to defend yourself,” he told CBS News.

Look, you right wing, NRA-affiliated prat, if he couldn’t have obtained the gun in the first place just by showing his ID (and reports suggest he didn’t even have to do that because he bought it online), this almost certainly wouldn’t have happened – like with most of the mass shootings your country is famous for. How the f**k does anyone over there have the ‘right to bear’ an assault rifle? It’s designed to kill people. Period.

It is lack of gun control that has led to it, and lack of gun control which continues to fuel it.

And what Paxton has said is doubly stupid given that the situation is still ‘live’, and no one could possibly know enough about the shooter to determine his motives at this time, and thus conclude so absolutely that his actions weren’t preventable. Gun control would have likely prevented at least some of the 251 people who have already died in mass shootings in the US this year.

We don’t have mass shootings in the UK to anything like the level they do in the USA. Over here, it needs a special kind of psychopath with an especially deep sexual inadequacy to get hold of a gun and kill a lot of people all at once. In America, you can get a gun with your corn flakes, and if it then turns out you’re also inadequate, you’re already tooled up for what comes next.

And I woke up this morning to discover that as well as the 20 dead in El Paso, another 9 have been killed in a separate incident a few hours later in Ohio. The jackass this time was carrying a high-capacity assault rifle and extra magazines.

Gun control is the only answer. Not the full answer – but a damn sight better one than what they have right now.

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Driving Test SuccessI recently saw an ADI claim that theory test apps are no good because they “only cover 5%” of the possible questions. It’s yet more complete bollocks from so-called “professionals”, and is only true – and even then, only partially – if you (or your pupil) is an idiot.

The only app I recommend to all my pupils is Driving Test Success (DTS), which is published by Focus Multimedia. I have no affiliation with Focus whatsoever – though an agent of theirs did once contact me offering such a relationship, but I never heard from him again. The full version of DTS contains all the official DVSA revision materials, and unless they are telling lies, that means exactly what it says. They also do a free “taster” version, and that only contains about a third of the total questions in the official question bank (that’s about 30%, and not 5%).

Most of my pupils buy DTS if they haven’t already got something else – some will already have the DVSA one, which is perfectly OK, and which also contains all the relevant revision material. They all pass if they use either of these.

The important word in all this is “buy”. If you wanted to get hold of the raw bank of official questions from DVSA and use it or distribute it in any way, you’d have to pay. I know, because I have looked into it myself. You can register and get the question bank for free to play around with, but the moment you start giving anyone access to it you have to pay a licence fee per unit/user to the  to DVSA. If you wanted the Hazard Perception (HPT) clips, it’d cost you £800 up front just for those. You have to be approved to get the raw materials in the first place, and I asked if licensing charges would still apply if I only gave access to my own pupils. They said it would. So any official revision software would incur those same costs for the publisher.

Several years ago, I had advised a pupil to get DTS for his phone. I specifically said to get the one that cost £4.99, and not to download the free one, because it was just a trial version that didn’t have all the questions in it (at the time, it may well have contained only around 5% of the full question bank). He subsequently kept failing his theory test, and I was pulling my hair out as to why – I asked him about his school lessons, possible dyslexia and stuff, everything. He assured me there were no issues, and that he was getting 100% every time he did a mock test. After he failed for about the sixth time with a score that you could have bettered by guessing, something clicked, and I asked “how much did that app cost you?” He replied “oh, nothing. It was free”. I think my reply was something along the lines of “you prat! I told you that was a trial version”.

It turned out he’d been answering the same incomplete sample of questions over and over again (he said he wondered why he kept seeing the same ones). It was no wonder he was getting 100%. Once he bought the full version – with all the questions in it – he passed the next time.

ADIs who make stupid claims about apps only containing 5% of the questions must be of a similar mentality to that pupil. They expect free versions to be the full monty, and stupidly assume that when they aren’t then this must be true of all apps whether paid for or not. God only knows how they qualify as ADIs if they are so dumb. I figured out what “trial” meant the first time I saw it – particularly when there was the paid-for version sitting right next to it in the Android market, prompting the immediate question: why?

The only thing you need in order to pass the Theory Test is the DTS Bundle. It costs £4.99, and includes the Hazard Perception (HPT) clips. The official DVSA one is also fine and costs the same, though I haven’t used it in a long while.

There are some free ones which claim to contain all the questions, though those I’ve seen don’t have the HPT included. They contain advertising and “in-app purchases”. As I say, someone somewhere has to pay.

Frankly, for the sake of £4.99, and the risk failing the £23 Theory Test a few times because you didn’t have the right revision resources, you should stop pissing about and just buy it.

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Media manipulated test pass ratesA few days ago, the media was awash with reports about how the driving test pass rate had plummeted, and it was all because of the “new parallel parking manoeuvre” that had been introduced. It was a great opportunity for ADIs who have been against “it” from the start to give their two penn’orth.

Although the link above was from The Telegraph, the Daily Mail ran the same illiterate crap, and several others followed. Comic news site, Yahoo, even went so far as to blame the same “new” manoeuvre on a separate FOI request, which revealed one candidate took 21 tests in a single year.

It seems that in the world of newspapers, someone who has just been given their first job in journalism does one of these FOIs every year. I think it must be some sort of induction test to make sure they can fill in an online form properly. And every year, without fail, there is someone somewhere who has taken an ungodly number of tests before passing (and some of them still haven’t passed, even then). It is a separate statistic which is independent of how easy or hard the test is. It merely shows that just as some people are crap journalists, there are others who are crap drivers and perhaps ought never to be allowed to drive. Ever. But it is separate.

The really laughable part is the reference to this “new parallel parking manoeuvre” – all the more laughable since there are ADIs who have allowed themselves to be associated with the claims. Because there IS no new parallel parking manoeuvre! Even some joker representing a querulous organisation which, in a previous incarnation, specialised in stirring things, ranted about how “dangerous” it is without clarifying the glaring naming error (perhaps because he didn’t know himself).

What there actually is is a piss-easy manoeuvre which involves checking your mirrors and looking ahead to make sure it’s clear, pulling over on the right-hand side of the road, then reversing back a couple of car lengths without ending up on the pavement or on the other side of the road again, and finally driving off and going back over on to the correct side safely. It’s the kind of thing any 17 year old is going to be doing 5 minutes after he passes when he sees one of his mates on the other side of the road.

The manoeuvre is referred to as “pulling up on the right”, “stopping on the right”, or similar phrases. And it is not a “parallel parking manoeuvre”.

It’s only dangerous if people haven’t been taught to do it properly. Mine have to do it on busy roads in Long Eaton and with oncoming/passing/parked lorries on a busy industrial estate in Colwick, and the only problem I’ve had was when someone decided for reasons not even known to himself to turn the wheel on to half lock as he reversed and veered outwards (and since he didn’t notice until I showed it to him on the dashcam, it was probably best he was caught early anyway). A disproportionate number of tests seem to include it, and I thought they’d pull back on it after the original introduction – where virtually every test did it – but they haven’t.

The media has claimed that the pass rate has plummeted. They base this ridiculous statement on something like the graph at the top of this article – which shows the national pass rate for the last three years. I have carefully adjusted the axes to make it look as bad as possible, just like pretty much every journalist does when they’re talking about numbers. Yet it is only a little over 1% decline over three years. If you ignore the fact that life has been going on for more than the last three years, it looks like the pass rate is on a downward slope into oblivion – even if it would take over 40 years to get to zero at the rate it is going.

However, if you look at pass rates since the introduction of the driving test in 1935, a completely different story emerges.Official pass rates since 1935

I cut these data down to one approximately every 5 years up until 2007, and from there on the data are yearly. Because of that, and also because I started the y-axis at 20% instead of 0%, they look a bit more dramatic than they are (i.e. the right half of the graph covers 19 years, whereas the left half covers 65 years – imagine the 1935-2000 part stretched out to three times wider).

Something odd happened between 1975 and 1990, and between 1990 and 2000 (a rise followed by a fall). But since 2000 the pass rate has been virtually flat – hovering between 44% and 47%. It is currently at about 46%, and there are no blips or drops worth a mention (i.e. any changes to the test have neither improved or worsened pass rates to any significant extent).

As I said, the top graph shows what you can do if you don’t represent data properly, and the message that comes across if you’re an ADI or journalist who doesn’t understand data is both confused and wrong.

The only time the pass rate has been significantly higher than it is now was in a different era. No internet, no smartphones, dial phones wired to the house, two postal deliveries a day (one of them before you got up), bottled milk on the doorstep, outside toilets, bin men who actually carried bins overflowing with filth and tipped them in the back of a truck, anything up to 1,000 times fewer cars on the road, no motorways, no roundabouts, and so on. DVSA does itself no favours harping on about training standards being the issue when the pass rate is hovering around 45%. It’s just the norm, and has been for almost 20 years – and up to more than 50 years if you allow a few percent extra variance.

One thing is certain. The pass rate has not fallen (or risen) significantly for the last 20 years. And the proper graph clearly shows its not likely to change much in the next 20 either – unless some idiot forces it to. I try not to say bad things about them, but I’m sure DVSA is disappointed that the 2019 data point isn’t joined by an almost vertical line up at 90%, and will likely blame this on poor training again.

Oh, I almost forgot to mention. The reason I wrote this is that DVSA has had to send out an email correcting the false media stories.

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The Chillmax AirEarly in July, I saw this thing advertised on TV. Then, the same evening, I was shopping in Asda and saw it on display. I am an idiot for things like this, and bought it on impulse so I could test whether it worked or not.

As a chemist, I know full well that if you want to cool a large space down effectively you’re going to need something that uses a special refrigerant. From a practical perspective – where people are going to be in that space, and you need to cool for long periods – that’s going to mean some sort of motor-driven compressor, a closed radiator filled with the refrigerant, a big fan to suck air in and blow it across the radiator, and a wide exhaust pipe through the wall or window to get rid of the “removed heat”. Oh, and probably some sort of collection bucket for the condensed water it takes out, because proper air conditioners dehumidify the air they cool.

The Chillmax Air is much simpler. Anyone who has used a normal fan will know that you only feel “cooler” if you’re sweating. That’s because the fan evaporates your sweat, and that evaporation is accompanied by a small cooling effect – it’s called “evaporative cooling”. Conversely, if the surrounding air is very humid, then no matter how powerful your fan is, you will feel little or no cooling because sweat can only evaporate if the air has capacity to hold additional moisture (I’ll explain that a bit more later).  This same evaporative cooling effect can even be used to freeze water – albeit in very small amounts (and if you’re lucky) – when you force diethyl ether (the stuff they used to use as an anaesthetic) to evaporate quickly. The evaporative cooling effect of different liquids varies greatly, and ether will cool down to a very low temperature if you do it properly. However, ether is both highly flammable and toxic, so apart from demonstrating it in the school lab (where I remember it from, along with the massive headache it gave me), it doesn’t have much practical application these days (though early refrigerators used it, which was spectacularly dangerous).

The Chillmax Air uses the evaporative cooling effect of water. The unit consists of a reservoir at the top, which you fill with normal tap water, and this drips down on to a radiator unit which has ten sideways-stacked fibre panels in it through which a fan blows air. The water evaporates from the fibre panels, and the evaporatively cooled air comes out through the front grille. According to the marketing spiel on the TV ad, you’d be forgiven for thinking you’re going to get frostbite if you sit too close. I knew this wasn’t going to happen – but I wanted to know just how effective the Chillmax Air was.

When I set it up and turned it on, the first thing I noticed was that the fan is quite powerful, so you get a good flow of air directed at you – but note that that it’s only about 5″ in diameter, so it can’t beat a proper desk fan for air flow. The next thing I noticed was that the air did seem a little cooler compared with what my desk fan was blowing at me. It also felt different in another way, which I’ll also come to later. But the big question was how much cooler was the exhaust air?

I fired up my trusty data logger and left it in front of my desk fan for 30 minutes for the control data. Then I moved it and suspended it in front of the Chillmax for the same period of time. This is what it recorded (red line is the switch over point).Chillmax Air - temperature recording

The ambient temperature where I ran the test was about 26ºC (it rose by about half a degree because I had entered the room, turned on the TV and my PC, and so on). The Chillmax brought this down by about 2.5ºC (the blip at the end is where it had just run out of water and was starting to warm up again, and I estimate that it might have dropped another degree at most).

So, the Chillmax definitely cools the air that passes through it, albeit by a small amount. Let’s work on the assumption that it would be able to get the same 2.5-3.5ºC drop no matter what the ambient temperature was. It’s for you to decide if that’s worth the investment, but be aware that if the ambient temperature is 38ºC, pulling it down to 35ºC still means it’s damned hot.

But there’s a little more to it than that. I mentioned that the exhaust from the Chillmax felt different to what my fan was throwing at me, and not just cooler. If I was going to try and put a word to it, I’d say it felt softer. I already knew what it was, but my data logger shows it in numbers.

This is the data for relative humidity recorded at the same time as the temperature measurement, above (red line is the switch over).Chillmax Air - relative humidity recording

As I’ve already explained, the Chillmax works by evaporating water on fibrous panels by forcing air across them. So where does the water go once it has evaporated? Quite simply, it comes out as a vapour in the cooled air. Well, most of it does. Some of it actually condensed on to my data logger and began to drip during my test. I have since discovered that it also condenses on the front grille and can drip periodically, so you need to be careful if you put it on a shelf with, say, your laptop underneath. This is especially true if you’ve set the grille (which is adjustable) to aim slightly downwards, which you probably would do if it was above eye level. And the fan is quite powerful enough to project the drips forward when they drop.

The ambient humidity in the room where I did the test was about 43%RH. The Chillmax sent that up to nearly 58%RH. The drop at the end is where the water ran out, and it is likely that it would have settled around 60%RH. And that was why the air coming out of it feels softer – it’s more humid than the air being sucked in. When you turn the Chillmax on, you can actually see the vapour in the right light – it’s basically fog.

It’s this raised humidity of the cooled air which really brings into question whether the Chillmax is worth the investment. Most people will know that you can have a hot summer day in the high 20s where it is comfortable and pleasant, and another – perhaps slightly cooler – one which is really sticky and sweaty. That’s because of the humidity, or water vapour in the air.

The amount of water vapour that air can hold varies with the temperature. At very low temperatures, air might only be able to hold a few milligrammes of water per kg, but at higher temperatures this can go up to nearly 100g per kg of air. People generally refer to this as “the humidity”, but the important measurement – and the one people are probably referring to without realising it – is the relative humidity (RH). This is the amount of water in the air expressed as a percentage of the maximum amount it could hold. When the RH hits 100% (more or less the dew point, though there’s a bit more to it than that) at any temperature, then any additional water will condense out immediately. It’s why your car windscreen fogs up in winter as soon as you get inside, because the air is already close to 100%RH and your breath and perspiration immediately causes the dew point to be exceeded. But even below the dew point, you can still get some condensation if there are nuclei which promote it (such as data loggers and the grille on the front of the Chillmax). But the most important detail in all this is that at higher temperatures, high RH is uncomfortable.

The real issue with evaporative cooling comes with changes of temperature when it is already humid. If it is 30ºC outside and 90%RH, dropping the temperature by 3ºC will send the RH up automatically – possibly hitting the dew point there and then. But if you are adding another 500g of water (which is how much the Chillmax holds when you fill it up), and as my data logger showed, you’re pushing the RH up by at least another 10%. On a hot and sticky day, and with the air unable to hold any more moisture, you’re likely to notice dampness when using the Chillmax (I noticed it even in this test). And as I have already mentioned, when the RH is high evaporative cooling from your sweat is less effective, so you would actually feel more uncomfortable even though the air is a few degrees cooler.

Proper air conditioners remove water from the air they cool – so much so that the best ones have humidifiers in them to stop the cooled air from being too dry. In my car, for example, if I have the A/C on the lowest temperature setting my lips start to feel sore because they’re losing moisture, and other people say that it dries their hair out. Proper A/C units use a special refrigerant the same as you get in fridges and freezers, and they cool the inlet air so much that the RH goes beyond the dew point and most of the water condenses out – that’s why you get a pool of water under your car if you stop with the air conditioning turned on in humid weather (or have problems with them icing up if they’re badly drained). It’s also why it is nice and comfy inside an air-conditioned car (apart from your lips) when it’s hot and sweaty outside, even if you have your A/C set at a normal temperature rather than deep-freeze mode most people use. Dry air feels crisp, whereas moist air feels… well, softer. Almost like a sauna if it’s hot enough. The Chillmax does the opposite of normal A/Cs, and adds moisture.

Aesthetically speaking, the Chillmax is a cube – more or less – about 15cm along each side. There are two buttons on the top rear, one which changes the fan speed to one of three settings (or off), with a blue LED for each, and another button that turns the night light on or off. There’s a flap on the top front through which you add the water. The radiator system is a plastic-framed insert which you access by pulling the front grille out. It slots in and out easily. You can’t replace the fibre inserts in the radiator (well, I think you could if you could get hold of them), but you can buy the whole radiator assembly from JML for £15. My only major gripe is the power cable. The jack plug that goes into the Chillmax is quite stubby and doesn’t go into the socket very far, so it is easy to dislodge it. However, the cable itself is quite long, and the  mains plug is a moulded UK type.

JML claims the Chillmax can run for up to 10 hours per fill, but this is undoubtedly on the lowest of the three fan speeds. At top speed, it runs out in less than three hours. To be fair to it, you do still get a noticeable cooling effect on the lowest speed, and since the water lasts longer then, less of it will be getting pumped into the air at any one time, and that might offset what I said about humidity very slightly – but it’s still being pumped out.  JML sells the humidification as a positive without relating it to the comfort relationship between temperature and RH, but note what I said above. If you want to cool down in humid weather, it probably isn’t just the temperature that needs to come down, certainly not a mere 3ºC drop, and definitely not if that means pushing high humidity even higher.

Update #1: I have now tested it in what I considered to be hot and sticky conditions – the kind of weather that means you’re sweating even when sitting still.

Here’s the temperature log (red line again shows the switch over between desk fan and Chillmax.Chillmax - temperature log in hot and sticky conditions

The Chillmax still achieved a similar temperature drop to the initial test. However, the air did not actually feel any cooler blowing on my face. If anything, it was more uncomfortable, though this is a subjective comment. The graph for Relative Humidity below explains why.

Chillmax - RH log in hot and sticky conditionsThe ambient RH was similar to last time, but the Chillmax sent it up to about 70% (a larger jump than in the first test). This is why there was no noticeable improvement in comfort – the small temperature drop was cancelled out by making the air much more humid (i.e. sticky).

You might find the Chillmax useful. It’s quite a smart little device – it’s not a Rolls Royce build, but it’s not badly made for what it is – and not that noisy (but you can hear the fan on the top speed). It certainly cools the air. A little, at any rate. Unfortunately, the increase in humidity that goes along with that cooling definitely seems to cancel it out out at higher temperatures.

Update #2: I tried it in the latest heatwave (33ºC outside on 23 July) and you can’t feel any cooling effect at all.

Update #3: Right! That’s it! That “latest heatwave” maxed at 38°C indoors on 25 July, and even now – 1am on 26 July – it’s 36°C at 50%RH and I feel The Devil biting my ass. The last thing I want is to send the RH up to 90% using the Chillmax to get the temperature down to only 33°C. God knows how I’m going to sleep tonight. So I have a proper air conditioner arriving tomorrow – watch out for a review of that.

Does it really work?

Well, it does cool the air by a few degrees, but it also sends the humidity up. So if it is already humid and sticky, the cooling effect is completely cancelled out by the extra stickiness. You might get away with that if your windows are open and there’s a through-draught in your house (or personal space), but if it’s also very hot you may not see any benefit at all.

It definitely doesn’t do what you might think it does from those TV ads. It would be fine if it just cooled, but the fact that it also humidifies is the main problem you’re likely to experience.

From my own use of it, I would say that it is a better humidifier than it is a cooler – especially when it is very hot, which is the last thing you want.

Will it cool more if I use ice water?

No. Evaporative coolers are not influenced significantly by the temperature of the water used in them. The temperature of the air that comes out depends on the temperature (and humidity) of the air going in, and the science of evaporation.

Can I use it to cool my PC?

Someone found this article on the search term “jml chillmax air for pc cooling”. If they mean what I think they mean, no, there is absolutely no way you want to be blowing damp air into your PC.

They might have meant powering it from a PC. The mains adapter is rated 5.0V at 1.8A, so assuming the Chillmax does draw 1.8A (and it probably doesn’t, as this is the maximum rating of the adapter) then your PC couldn’t supply that current from a USB port. USB ports are rated at 0.5A or 0.9A depending on the type. Dedicated charging USB ports can handle up to 1.5A, and although that’s a close call (the fan in the Chillmax looks like a computer fan), personally I wouldn’t risk trying to power it from a PC.

Can you get larger versions?

You can certainly get larger evaporative coolers. The working principle is that the larger the surface area of water, and the greater the airflow over that water, then the greater will be the possible drop in temperature at the front end. However, cooling effectiveness is influenced greatly by the RH of the air going in.

If the air is very dry, then a large evaporative cooler might be able to drop inlet air at 30ºC down by as much as 10ºC. However, if the inlet air is very humid, the temperature drop could be as little as 1ºC. In the UK, the realistic temperature drop you could expect on a non-humid day for a large cooler would be around 5-6ºC, but on a sticky day you’d only get about a 3ºC drop.

Suppliers of these devices say that they need good ventilation or extraction, and I would imagine that’s so the humid air can escape. If you’re evaporating more water to get better cooling on larger devices, you’re also producing a lot more water vapour.

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Audi embedded in houseA DVSA alert came through yesterday informing us that they’re investigating the possibility of introducing graduated driver licences (or something along those lines). Again.

First of all, let’s look at the facts surrounding this news (i.e. what’s actually in it, and not what the media headlines are saying).

  1. They’re only exploring the possibility. It won’t happen anytime soon.
  2. There will be a consultation before – and if – any changes are made.
  3. They are talking about new drivers’ “first few months on the road”.
  4. They don’t know exactly what – if anything – will be introduced.
  5. “New drivers” means everyone, and not just 17 year olds.
  6. Any changes would be for future new drivers.
  7. The impetus for this comes from the Government, and not DVSA per se.

Don’t forget that it took over 40 years to get learners able to go on the motorway, and even in my time as an ADI there were numerous “nearly” moments within different governments. Even the final kickstart took over two years to implement.

So why is the issue of graduated licences coming up once again?

Data show that 20% of new drivers have a significant accident within the first 12 months of passing their test, and it is that statistic which is being addressed. However, if we look at separate data, which has been reported many times previously, there is an enormous blip in the accident statistics where the following points are identified from individual cases of those involved:

  • 17-25 year old
  • male
  • rural road
  • on a bend
  • at night
  • more than one occupant in the same age group
  • excessive speed involved
  • no other vehicle involved

If you translate this data, it basically means young show-offs with little experience driving too fast for their skill set, distracted by their mates, and whipping the wheel round to take a bend they only saw as they entered it, then spinning off into a tree or field. Frequently, at least one passenger is fatally injured. Although males feature highly in these figures, females are still represented, where the distraction is often slightly different but equally stupid. This whole scenario is why insurance is so high for that age group.

It comes down to inexperience. Inexperience of driving, and inexperience of self-preservation. And whether you like it or not, it applies to more 17 year olds than it does 40 year olds – a) because there’s more of them, and b) 17 year olds are more likely to exhibit behaviours which compound their inexperience. The whole issue is about actual accidents and actual deaths. It’s not some random game to moan about because you think your son or daughter is an angel and shouldn’t be treated in a manner that you consider to be unfair.

I’ve mentioned this before, but many years ago I had what was then my best ever pupil. He was a smart lad, from a wealthy (-ish) family, high-achiever at school, pleasant (as was the whole family), and a quick learner. He was an excellent driver when he passed his test first time after only 23 hours of lessons. And he promised me he’d drive safely.

His mum wanted him to do Pass Plus, because she was concerned at his lack of experience – a sentiment I readily agreed with because he’d passed so quickly. Six weeks later – during which time he’d been driving in the beaten-up little Fiesta his mum had bought him – I was amazed at how far he’d drifted away from what I’d taught him. He was cornering too fast and taking chances when crossing the path of other traffic. I pulled him back during the Pass Plus and left him with some words of wisdom once it was completed.

Sometime after, I began teaching his then girlfriend, who his mum had referred to me. The girlfriend told me that he had already damaged his car by hitting a kerb cornering too fast (he hadn’t told me that), and that when he was out with his mates he would drive very fast, sometimes over 70mph in 30mph zones (he didn’t tell me that, either). I was concerned for her, but she said he’d never do it with her or with his mum in the car, because his mum would kill him if she knew. And I can promise you that he was in no way unique. Some of those I’ve taught since have made it absolutely clear how they’re going to drive when they pass. And they do.

And that’s why something has to be done. Far too many young people behave like this as a matter of course. They know full well they are in the wrong (which is why they hide it), but they do it nonetheless because it gives them street cred with the other monkeys in the jungle, and is the next best thing to sex for a 17 year old. Being inexperienced doesn’t enter the equation as far as they’re concerned. It’s no use pretending that your little darling doesn’t do it, because he or she almost certainly does to some extent. I even saw an ADI making this claim. Quite frankly, if a teenager is in rebellion mode – as many are – being the offspring of an ADI might even increase the likelihood of them behaving like prats.

So although I think DVSA isn’t addressing the root of the problem, it is at least trying to deal with the possible outcomes of that problem. Any restrictions placed on new drivers would at least give them time to gain some experience before they’re let off the leash, and the testosterone (or oestrogen) is able to kick in fully.

Not all young people are dangerous

Potentially, yes they are. They are inexperienced, and that alone is enough to lead to errors of judgment. Bad behaviour just compounds it.

When I was younger, going skiing every year was risky and fun, and resulted in a broken collar bone the first time I did it through going too fast when I was still crap. I discovered that snow-ploughing at speed (i.e. as fast as possible) over moguls on a glacier in Verbier with almost no surface snow down a black run is actually not as good an idea as I had originally thought. At the time, having the entire lift system shut down so mountain rescue could get me off the glacier and to the hospital, then being temporarily disabled and off work for a few weeks when I got back was a badge of honour. These days (and as soon as the following year, in fact), I would see it as bloody dangerous and wouldn’t be that stupid again – even though I’m a much better skier. Being unable to drive and off work now would be a royal pain in the ass, and enormously embarrassing. That’s what maturity and experience does to you.

It’s unfair to penalise only young people

They’re not. They are talking of penalising all new drivers. The fact that younger drivers would be most affected is a statistical thing, as is the fact that 20% of new drivers have a significant accident in their first year of driving.

I see older drivers driving more dangerously

That’s a separate issue. The one being addressed here is lack of experience.

My son (or daughter) doesn’t drive like that

This makes me laugh. Yes they bloody well do! Inexperience, by definition, applies to all new drivers. Furthermore, unless you are with them every time they drive, you haven’t got a clue what they get up to. I’ve lost count of the times some prat (often with “P” plates on) has pulled out in front of me or cut me up, and the only reason there hasn’t been an accident is because of my anticipation and reactions (both as a driver, and as an ADI using the dual controls). Those drivers could easily be your son or daughter. You have no knowledge of it and no control over it whatsoever. In my opinion, coming out with this statement is one of the contributing factors as to why there is a problem in the first place (along with letting them have an Audi or BMW as their first car).

Actually, that’s another thing. The only reason anyone buys an Audi (or BMW) is to drive fast, so a new driver who gets one is not going to be sticking to the speed limit or driving cautiously. The only time you’re likely to be stuck behind one being driven slowly is when the driver is texting or pissing about with the stereo. The rest of the time, they’ll be trying to get in front. You can argue as much as you want about that, but it is a simple fact. I see it every day.

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