It occurred to me today, having finally got the aircon fixed, that
aircon introduces another dimensions into MPG calculations.

It is generally reckoned that a car with windows closed has less drag
than one with them open, but adding aircon adds a *constant* power
drain, irrespective of car speed.

Which means for best MPG you want to travel *faster* with aircon, than
without it. In order to shorten journey times and hence energy loss per
mile from the aircon.

--
“A leader is best When people barely know he exists. Of a good leader,
who talks little,When his work is done, his aim fulfilled,They will say,
“We did this ourselves.”

― Lao Tzu, Tao Te Ching

On 16/09/2023 22:20, The Natural Philosopher wrote:
> It occurred to me today, having finally got the aircon fixed, that
> aircon introduces another dimensions into MPG calculations.
>
> It is generally reckoned that a car with windows closed has less drag
> than one with them open, but adding aircon adds a *constant* power
> drain, irrespective of car speed.
>
> Which means for best MPG you want to travel *faster* with aircon, than
> without it. In order to shorten journey times and hence energy loss per
> mile from the aircon.
>
>
>
I'm afraid that there's rather a serious flaw in that argument. Whereas
the aircon itself may use less energy by that method, the engine is
likely to use *more*. The faster you go, the higher the tractive effort
required to overcome the drag. Remember that aerodynamic drag is
proportional to the square of the speed. Since work done (= energy
consumed) = force x distance, the energy consumed per mile will increase
with speed, as the drag increases.

This, in turn, leads to more fuel consumed per mile - i.e. lower MPG.
This may be partially offset if, by going faster, you can run the engine
at a more efficient point on its fuel map - but the overall effect is
still going to be less MPG the faster you go.

The best way of saving fuel is to travel for long distances at a
constant speed without a lot of starting and stopping or accelerating or
braking. My car achieves far better MPG at a steady 70mph on a motorway
that it does around town at a far lower average speed. *But* just to
emphasise the point made above, it does far better still at a constant
60pmh - all with the aircon on all the time.
--
Cheers,
Roger

On 16/09/2023 23:09, Roger Mills wrote:
.. *But* just to
> emphasise the point made above, it does far better still at a constant
> 60pmh - all with the aircon on all the time.

On many UK motorways travelling at a constant 60 usually means a HGV in
front of you, A HGV up your arse and a HGV beside you for the miles it
takes it to overtake at 60.05 mph. :)

--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

On 16/09/2023 22:20, The Natural Philosopher wrote:
> It occurred to me today, having finally got the aircon fixed, that
> aircon introduces another dimensions into MPG calculations.
>
> It is generally reckoned that a car with windows closed has less drag
> than one with them open, but adding aircon adds a *constant* power
> drain, irrespective of car speed.
>
> Which means for best MPG you want to travel *faster* with aircon, than
> without it. In order to shorten journey times and hence energy loss per
> mile from the aircon.

The general rule of thumb used to be - below 40mph, open windows are
more efficient than aircon and above 40mph it is the other way around.

On 16/09/2023 23:57, SteveW wrote:
> On 16/09/2023 22:20, The Natural Philosopher wrote:
>> It occurred to me today, having finally got the aircon fixed, that
>> aircon introduces another dimensions into MPG calculations.
>>
>> It is generally reckoned that a car with windows closed has less drag
>> than one with them open, but adding aircon adds a *constant* power
>> drain, irrespective of car speed.
>>
>> Which means for best MPG you want to travel *faster* with aircon, than
>> without it. In order to shorten journey times and hence energy loss per
>> mile from the aircon.
>
> The general rule of thumb used to be - below 40mph, open windows are
> more efficient than aircon and above 40mph it is the other way around.

*More* efficient than what? Cooling the car's interior? If that's what
you mean, surely it's the other way round. The faster the air flow, the
cooler it will appear to be. You lose heat by evaporative cooling, so
the faster air flow will remove sweat more quickly.

One question though - is it better to have the aircon recirculating the
cooled internal air, or better to have fresh air being cooled all the
time? I guess it depends on the outside temperature and how quickly the
car's interior suffers from any "greenhouse" effect and perceived
"stuffiness" with closed windows. I always have fresh air coming in
(although in the past when stuck behind a smoking, stinking diesel I
would close the outside vents).

--

Jeff

In message <kmmnd0Fce40U1@mid.individual.net>, Roger Mills
<mills37.fslife@gmail.com> writes
snip
>
>The best way of saving fuel is to travel for long distances at a
>constant speed without a lot of starting and stopping or accelerating
>or braking. My car achieves far better MPG at a steady 70mph on a
>motorway that it does around town at a far lower average speed. *But*
>just to emphasise the point made above, it does far better still at a
>constant 60pmh - all with the aircon on all the time.

Momentary idle thought.. presumably lines of traffic travelling at
similar speeds will create local air flows not linked to wind
speed/direction.

--
Tim Lamb

On 16/09/2023 23:20, alan_m wrote:
> On 16/09/2023 23:09, Roger Mills wrote:
> . *But* just to
>> emphasise the point made above, it does far better still at a constant
>> 60pmh - all with the aircon on all the time.
>
>
> On many UK motorways travelling at a constant 60 usually means a HGV in
> front of you, A HGV up your arse and a HGV beside you for the miles it
> takes it to overtake at 60.05 mph. :)
>
On a UK motorway HGVs are mechanically limited to *56mph* (90km/h).

The fact that it looks like 60mph to you is because 99.999% o9f all
speedometers read about 7% too high.

The process of one overtaking the other I call the "Commercial Two-Step"

(quick quick slow slow)

--
Microsoft : the best reason to go to Linux that ever existed.

On 16/09/2023 23:57, SteveW wrote:
> On 16/09/2023 22:20, The Natural Philosopher wrote:
>> It occurred to me today, having finally got the aircon fixed, that
>> aircon introduces another dimensions into MPG calculations.
>>
>> It is generally reckoned that a car with windows closed has less drag
>> than one with them open, but adding aircon adds a *constant* power
>> drain, irrespective of car speed.
>>
>> Which means for best MPG you want to travel *faster* with aircon, than
>> without it. In order to shorten journey times and hence energy loss
>> per mile from the aircon.
>
> The general rule of thumb used to be - below 40mph, open windows are
> more efficient than aircon and above 40mph it is the other way around.
>
That sounds about right for a 20 year old car...

I wonder if it holds today.

Anyone else remember air brakes aka 'quarter lights'

--
Microsoft : the best reason to go to Linux that ever existed.

On Sun, 17 Sep 2023 09:38:09 +0100, Tim Lamb wrote:

> In message <kmmnd0Fce40U1@mid.individual.net>, Roger Mills
> <mills37.fslife@gmail.com> writes snip
>>
>>The best way of saving fuel is to travel for long distances at a
>>constant speed without a lot of starting and stopping or accelerating or
>>braking. My car achieves far better MPG at a steady 70mph on a motorway
>>that it does around town at a far lower average speed. *But*
>>just to emphasise the point made above, it does far better still at a
>>constant 60pmh - all with the aircon on all the time.
>
> Momentary idle thought.. presumably lines of traffic travelling at
> similar speeds will create local air flows not linked to wind
> speed/direction.

If you really want to save fuel, you'd slipstream an HGV ... needs balls
of steel though.

On 17/09/2023 08:01, Jeff Layman wrote:
> One question though - is it better to have the aircon recirculating the
> cooled internal air, or better to have fresh air being cooled all the
> time? I guess it depends on the outside temperature and how quickly the
> car's interior suffers from any "greenhouse" effect and perceived
> "stuffiness" with closed windows. I always have fresh air coming in
> (although in the past when stuck behind a smoking, stinking diesel I
> would close the outside vents).

I think I would only recirculate when there was a need for massive
temperature change, quickly.

The build up of water vapour rapidly leads to high humidity which to an
extent reduces perceived cooling in hot weather and induces misting up
in cold weather...One of the less appreciated uses of aircon is to dry
extremely damp air by refrigerating it, and then heating it again.

--
How fortunate for governments that the people they administer don't think.

Adolf Hitler

On 17/09/2023 09:38, Tim Lamb wrote:
> In message <kmmnd0Fce40U1@mid.individual.net>, Roger Mills
> <mills37.fslife@gmail.com> writes
> snip
>>
>> The best way of saving fuel is to travel for long distances at a
>> constant speed without a lot of starting and stopping or accelerating
>> or braking. My car achieves far better MPG at a steady 70mph on a
>> motorway that it does around town at a far lower average speed. *But*
>> just to emphasise the point made above, it does far better still at a
>> constant 60pmh - all with the aircon on all the time.
>
> Momentary idle thought.. presumably lines of traffic travelling at
> similar speeds will create local air flows not linked to wind
> speed/direction.
>
Oh for sure. My first vehicle was a Bedford CA MkII van. Barely capable
of 70mph. Slipstreaming the big HGVs allowed me to tale my foot half off
the accelerator.
I will never forget my surprise when I first fitted a full set of radial
tyres, too.

Another 10% on mpg.

--
"Strange as it seems, no amount of learning can cure stupidity, and
higher education positively fortifies it."

- Stephen Vizinczey

The Natural Philosopher <tnp@invalid.invalid> wrote:
> It occurred to me today, having finally got the aircon fixed, that
> aircon introduces another dimensions into MPG calculations.
>
> It is generally reckoned that a car with windows closed has less drag
> than one with them open, but adding aircon adds a *constant* power
> drain, irrespective of car speed.

The aircon is not a constant load, at least on modern cars. The compressor
has a clutch or other mechanism that varies the amount of load it puts on
the engine belt, so it only takes the power it needs to maintain the cabin
temperature. On hybrids and EVs it's an electric compressor that achieves
the same thing.

Agreed it's not related to speed, merely to cooling load.

> Which means for best MPG you want to travel *faster* with aircon, than
> without it. In order to shorten journey times and hence energy loss per
> mile from the aircon.

A car a/c compressor consumes about 2 kW. An engine is ballpark 80-150kW.
So it doesn't take much increased speed (air resistance) to completely
negate any load from the compressor. Likewise from this it's not hard to
imagine that opening the windows could easily create more than 2kW of drag.

Theo

On 17/09/2023 09:52, Jethro_uk wrote:
> On Sun, 17 Sep 2023 09:38:09 +0100, Tim Lamb wrote:
>
>> In message <kmmnd0Fce40U1@mid.individual.net>, Roger Mills
>> <mills37.fslife@gmail.com> writes snip
>>>
>>> The best way of saving fuel is to travel for long distances at a
>>> constant speed without a lot of starting and stopping or accelerating or
>>> braking. My car achieves far better MPG at a steady 70mph on a motorway
>>> that it does around town at a far lower average speed. *But*
>>> just to emphasise the point made above, it does far better still at a
>>> constant 60pmh - all with the aircon on all the time.
>>
>> Momentary idle thought.. presumably lines of traffic travelling at
>> similar speeds will create local air flows not linked to wind
>> speed/direction.
>
> If you really want to save fuel, you'd slipstream an HGV ... needs balls
> of steel though.

And brakes at least better than the HGVs...and lightning fast reflexes.
Basically you can drive a reaction time away from the HGV.

Any loss of concentration could be a disaster though.

I used to do it back in the day, but these days I leave the longest
possible gap to traffic ahead.

--
"Socialist governments traditionally do make a financial mess. They
always run out of other people's money. It's quite a characteristic of them"

Margaret Thatcher

> I used to do it back in the day, but these days I leave the longest
> possible gap to traffic ahead.
>

I do that, but people keep pulling into it. Sigh.

On 17/09/2023 10:13, Theo wrote:
> The Natural Philosopher <tnp@invalid.invalid> wrote:
>> It occurred to me today, having finally got the aircon fixed, that
>> aircon introduces another dimensions into MPG calculations.
>>
>> It is generally reckoned that a car with windows closed has less drag
>> than one with them open, but adding aircon adds a *constant* power
>> drain, irrespective of car speed.
>
> The aircon is not a constant load, at least on modern cars. The compressor
> has a clutch or other mechanism that varies the amount of load it puts on
> the engine belt, so it only takes the power it needs to maintain the cabin
> temperature. On hybrids and EVs it's an electric compressor that achieves
> the same thing.
>
Nit picking. That's like saying that the average power input to a
heating system is not constant as your boiler switches on and off.

What I meant by constant was persistent and (on average) time invariant.

> Agreed it's not related to speed, merely to cooling load.
>
>> Which means for best MPG you want to travel *faster* with aircon, than
>> without it. In order to shorten journey times and hence energy loss per
>> mile from the aircon.
>
> A car a/c compressor consumes about 2 kW.

But not constantly eh?

An engine is ballpark 80-150kW.

Mine is up to 200kW

But not all the time. At cruise, most cars are running at at most about
20kW, and many a lot less.

2kW is a 10% change in mpg

> So it doesn't take much increased speed (air resistance) to completely
> negate any load from the compressor.

Again, no numbers, just wet finger waving.

Her are a few numbers someone else prepared earlier:

"I might be being dim, but for an approximation, can you take a car's
BHP and maximum speed (assuming no limiter) and work back from there?
Power required = velocity ^ 3.

Obviously your results are only good for a car of that weight and aero.

For example: my car can supposedly do 137mph with 165bhp (I should be so
lucky on either count), so were that idea valid and my maths correct,
it'd need a mere 22bhp to do 70mph. "

That sorta gybes with my recollection of many old cars that were around
40bhp that could do around 60mph with shit aerodynamics and cross ply tyres.

In fact a shade better. Ford popular 100E was 36bhp from a side valve
engine and had a top speed of 69.9mph

3-4KW on top of that for aircon would have made a 10% difference to mpg.

And if it was cruising at say half throttle at its comfortable 55mph
sort of speed at around 18bhp, adding another 3kW would reduce its mpg
by ~16%.

Likewise from this it's not hard to
> imagine that opening the windows could easily create more than 2kW of drag.
>

> Theo

--
“Puritanism: The haunting fear that someone, somewhere, may be happy.”

H.L. Mencken, A Mencken Chrestomathy

The Natural Philosopher wrote:

> On 16/09/2023 23:20, alan_m wrote:
>> On 16/09/2023 23:09, Roger Mills wrote:
>> . *But* just to
>>> emphasise the point made above, it does far better still at a constant
>>> 60pmh - all with the aircon on all the time.
>>
>> On many UK motorways travelling at a constant 60 usually means a HGV in
>> front of you, A HGV up your arse and a HGV beside you for the miles it
>> takes it to overtake at 60.05 mph. :)
>>
> On a UK motorway HGVs are mechanically limited to *56mph* (90km/h).
>
> The fact that it looks like 60mph to you is because 99.999% o9f all
> speedometers read about 7% too high.
>
> The process of one overtaking the other I call the "Commercial Two-Step"
>
> (quick quick slow slow)

I presume many have found a way around the limiters then? Many travel well
in excess of that speed.

--
Bob
Tetbury, Gloucestershire, England

Santa Claus has the right idea. Visit people only once a year. - Victor
Borge

On 17/09/2023 10:28, GB wrote:
>
>> I used to do it back in the day, but these days I leave the longest
>> possible gap to traffic ahead.
>>
>
> I do that, but people keep pulling into it. Sigh.
>
>
Indeed they do, and I am sure they thank you for it

One of the most dangerous things that happens is a nose to tail train of
cars all too nervous or underpowered to overtake the car at the front of
the queue, and you are neither, but you can only do it in two hops, but
the guy with the gap deliberately closes it when he sees you coming.

That's one of the reasons I like to run with an excess of horsepower.
50-100mph in a couple of seconds gets you past a LOT of nervous Sunday
drivers without the need to cut back in.

And it also means that you can be a quarter of a mile back with far
better visibilitu and still be past in a flash, if it's you at the queue
head.

--
There is something fascinating about science. One gets such wholesale
returns of conjecture out of such a trifling investment of fact.

Mark Twain

GB wrote:

>> I used to do it back in the day, but these days I leave the longest
>> possible gap to traffic ahead.
>>
>
> I do that, but people keep pulling into it. Sigh.

Annoying, innit. It's a bit like the sections of motorway marked with
arrows and "keep two arrows apart" signs - fat chance. Mind you, that's not
such a daft idea - if everyone suddenly backed off 2 arrows distance, the
end car in the queue might well have to engage reverse to cope.
--
Bob
Tetbury, Gloucestershire, England

Be nice to your children - they pick the nursing home.

On Sun, 17 Sep 2023 10:14:45 +0100, The Natural Philosopher wrote:

> On 17/09/2023 09:52, Jethro_uk wrote:
>> On Sun, 17 Sep 2023 09:38:09 +0100, Tim Lamb wrote:
>>
>>> In message <kmmnd0Fce40U1@mid.individual.net>, Roger Mills
>>> <mills37.fslife@gmail.com> writes snip
>>>>
>>>> The best way of saving fuel is to travel for long distances at a
>>>> constant speed without a lot of starting and stopping or accelerating
>>>> or braking. My car achieves far better MPG at a steady 70mph on a
>>>> motorway that it does around town at a far lower average speed. *But*
>>>> just to emphasise the point made above, it does far better still at a
>>>> constant 60pmh - all with the aircon on all the time.
>>>
>>> Momentary idle thought.. presumably lines of traffic travelling at
>>> similar speeds will create local air flows not linked to wind
>>> speed/direction.
>>
>> If you really want to save fuel, you'd slipstream an HGV ... needs
>> balls of steel though.
>
> And brakes at least better than the HGVs...and lightning fast reflexes.
> Basically you can drive a reaction time away from the HGV.
>
> Any loss of concentration could be a disaster though.
>
> I used to do it back in the day, but these days I leave the longest
> possible gap to traffic ahead.

That's one of the things a semi autonomous car could do ...

The Natural Philosopher wrote:

> On 17/09/2023 08:01, Jeff Layman wrote:
>> One question though - is it better to have the aircon recirculating the
>> cooled internal air, or better to have fresh air being cooled all the
>> time? I guess it depends on the outside temperature and how quickly the
>> car's interior suffers from any "greenhouse" effect and perceived
>> "stuffiness" with closed windows. I always have fresh air coming in
>> (although in the past when stuck behind a smoking, stinking diesel I
>> would close the outside vents).
>
> I think I would only recirculate when there was a need for massive
> temperature change, quickly.
>

In a stationary car is the only safe way - you would get quickly anoxic and
become a danger to yourself and everyone else if you kept it on recirculate
whilst driving along for some time.

> The build up of water vapour rapidly leads to high humidity which to an
> extent reduces perceived cooling in hot weather and induces misting up
> in cold weather...One of the less appreciated uses of aircon is to dry
> extremely damp air by refrigerating it, and then heating it again.

It is only the recent fuel price increases that have persuaded me to ever
turn mine off, and then not very often. A nice cool, ventilated car is
about the biggest contribution to safety on the roads that one can make. As
you remark, demisting on a damp winter's morning takes a fraction of the
time with the aircon left on. I often wish some of the morons who drive off
with one tiny hole in the condensation on their windscreens knew that.
However, I suspect that comes under the old rule that education cannot cure
stupidity.

--
Bob
Tetbury, Gloucestershire, England

Be careful about reading health books. You may die of a misprint. - Mark
Twain

On 17/09/2023 10:13, Theo wrote:
mile from the aircon.
>
> A car a/c compressor consumes about 2 kW.

Why does it consume so much? In a house, a 2kW air conditioner will
easily cool a room of 40 - 50m^3 without problem. A car's interior will
be a tenth of that, so is a car's a/c just inefficient?

--

Jeff

The Natural Philosopher wrote:

> On 16/09/2023 23:57, SteveW wrote:
>> On 16/09/2023 22:20, The Natural Philosopher wrote:
>>> It occurred to me today, having finally got the aircon fixed, that
>>> aircon introduces another dimensions into MPG calculations.
>>>
>>> It is generally reckoned that a car with windows closed has less drag
>>> than one with them open, but adding aircon adds a *constant* power
>>> drain, irrespective of car speed.
>>>
>>> Which means for best MPG you want to travel *faster* with aircon, than
>>> without it. In order to shorten journey times and hence energy loss
>>> per mile from the aircon.
>>
>> The general rule of thumb used to be - below 40mph, open windows are
>> more efficient than aircon and above 40mph it is the other way around.
>>
> That sounds about right for a 20 year old car...
>
> I wonder if it holds today.
>
> Anyone else remember air brakes aka 'quarter lights'

For those of us stupid enough to drive whilst smoking (mea culpa) they were
a godsend. I only partially excuse myself on the grounds that a) everyone
did it and b) the roads were relatively empty then.

--
Bob
Tetbury, Gloucestershire, England

Doctor: I don't like the looks of your wife at all.
Husband: Me neither doc, but she's a great cook and really good with the
kids.

On 17/09/2023 10:47, The Natural Philosopher wrote:

> That's one of the reasons I like to run with an excess of horsepower.
> 50-100mph in a couple of seconds

Taking you more literally than you intended, I don't think there are
many production cars that could manage that - a McLaren F1 does 60-100
in 3.1s, for example.

On 17/09/2023 10:57, Bob Henson wrote:
> The Natural Philosopher wrote:
>
>> On 17/09/2023 08:01, Jeff Layman wrote:
>>> One question though - is it better to have the aircon recirculating the
>>> cooled internal air, or better to have fresh air being cooled all the
>>> time? I guess it depends on the outside temperature and how quickly the
>>> car's interior suffers from any "greenhouse" effect and perceived
>>> "stuffiness" with closed windows. I always have fresh air coming in
>>> (although in the past when stuck behind a smoking, stinking diesel I
>>> would close the outside vents).
>>
>> I think I would only recirculate when there was a need for massive
>> temperature change, quickly.
>>
>
> In a stationary car is the only safe way - you would get quickly anoxic and
> become a danger to yourself and everyone else if you kept it on recirculate
> whilst driving along for some time.
>
>> The build up of water vapour rapidly leads to high humidity which to an
>> extent reduces perceived cooling in hot weather and induces misting up
>> in cold weather...One of the less appreciated uses of aircon is to dry
>> extremely damp air by refrigerating it, and then heating it again.
>
> It is only the recent fuel price increases that have persuaded me to ever
> turn mine off, and then not very often. A nice cool, ventilated car is
> about the biggest contribution to safety on the roads that one can make. As
> you remark, demisting on a damp winter's morning takes a fraction of the
> time with the aircon left on. I often wish some of the morons who drive off
> with one tiny hole in the condensation on their windscreens knew that.
> However, I suspect that comes under the old rule that education cannot cure
> stupidity.

About 35 years ago I was driving a hire car in Hawaii, and getting used
to the aircon. The outside temp was around 30°, so I had it on pretty
high. Rather unexpectedly, the windscreen started steaming up, so I
turned the car ventilation airflow to the maximum demisting position.
The demisting got worse very quickly, so I tried wiping the windscreen
with my hand. It made absolutely no difference, and then the penny
dropped. I turned the windscreen wipers on and the screen became
instantly clear. The aircon was so cold that it had cooled the
windscreen glass down, and with the high humidity outside the
condensation was on that side of the screen!

--

Jeff

On 17/09/2023 10:44, Bob Henson wrote:
> The Natural Philosopher wrote:
>
>> On 16/09/2023 23:20, alan_m wrote:
>>> On 16/09/2023 23:09, Roger Mills wrote:
>>> . *But* just to
>>>> emphasise the point made above, it does far better still at a constant
>>>> 60pmh - all with the aircon on all the time.
>>>
>>> On many UK motorways travelling at a constant 60 usually means a HGV in
>>> front of you, A HGV up your arse and a HGV beside you for the miles it
>>> takes it to overtake at 60.05 mph. :)
>>>
>> On a UK motorway HGVs are mechanically limited to *56mph* (90km/h).
>>
>> The fact that it looks like 60mph to you is because 99.999% o9f all
>> speedometers read about 7% too high.
>>
>> The process of one overtaking the other I call the "Commercial Two-Step"
>>
>> (quick quick slow slow)
>
> I presume many have found a way around the limiters then? Many travel well
> in excess of that speed.

Not the class to which that diktat applies. It is literally more than
their job is worth with tachographs etc.

I know for a fact that coaches are not so limited.

Another factoid that not many people know is that goods vehicles (LCVs)o
are limited to 50mph on single lane roads. Not 60mph.

And 60mph on motorways. So that is basically 'vans not derived from a car'

None of them I have ever seen keep to either.

Which is why the HGVs are mechanically limited
A government report...

"4. On dual carriageways the actual average speed at which HGVs, such as
articulated lorries, travel in free flow conditions (when they are not held
up by other traffic or obstructions such as junctions, hills or bends) is 53
mph1. More than 80% of HGVs to which the 50 mph applies currently
exceed it in free-flow conditions2.

5. The average speed observed on motorways for these HGVs in free flow
conditions is also 53 mph, even though the legal speed limit for larger
HGVs on motorways is 60 mph. Free flow traffic data shows that 99% of
articulated lorries travel within 60mph. *A major reason for this is that
their speeds are limited by a speed limiter to 56 mph (90km/h) as
required by EU legislation.*'

The report basically says that the '10mph slower for commercial
vehicles' is disregarded by 93% of drivers, and the only thing that
works is EU mandated speed limiters.

Another advantage of Brexit would be to allow commercial traffic to
disable these on UK roads, thereby getting rid of the agonising road
blocks they cause.

--
"I am inclined to tell the truth and dislike people who lie consistently.
This makes me unfit for the company of people of a Left persuasion, and
all women"