Slow down

[vetran]

https://www.telegraph.co.uk/news/202...ls-no-10-told/

Cut motorway speed limit to 64mph to drive net zero goals, No 10 told


Plus, Philip Dunne calls on the Government for a ‘war effort’ on energy efficiency and reducing Britain’s dependence on oil

actually they have been trialling it for years

https://nationalhighways.co.uk/our-w...-limit-trials/

Apparently driving at 70 is 25% less efficient than driving at 64 which does seem to be odd.

[d000hg]

Well the US did that for decades though I forget if that was really about practicality or just politics?

Given that air resistance is proportional to speed squared you do see big savings for small changes in speed, another one I heard recently which seems unintuitive:

“We started with a car travelling at 30mph,” she told us. “We saw it drive towards us, and then perform an emergency stop. Using accurate police speed measuring equipment, we saw it do the same thing at 31mph , noting that it was still travelling at at 8mph when it passed the point where – at 30 – it would have stopped.

[Paddy]

https://www.telegraph.co.uk/news/202...ls-no-10-told/



actually they have been trialling it for years

https://nationalhighways.co.uk/our-w...-limit-trials/

Apparently driving at 70 is 25% less efficient than driving at 64 which does seem to be odd.

UK Motorways are also too conjected. Perhaps a 60mph limit from 6am to 8pm and 70mph outside these times.

[d000hg]

Getting to drive at a steady 70 is a dream for many. Constantly getting up to 70 then slowing and accelerating can't be good - and also leads to more jams with non-constant speeds (some chaos theory maths or something).

Though if you drive really close to the car in front you get a peloton effect and can save loads of cash.

[Zigenare]

https://www.telegraph.co.uk/news/202...ls-no-10-told/



actually they have been trialling it for years

https://nationalhighways.co.uk/our-w...-limit-trials/

Apparently driving at 70 is 25% less efficient than driving at 64 which does seem to be odd.

This makes interesting reading...

https://www.gov.uk/government/statis...avel-times-cgn

[vetran]

Well the US did that for decades though I forget if that was really about practicality or just politics?

Given that air resistance is proportional to speed squared you do see big savings for small changes in speed, another one I heard recently which seems unintuitive:

actually quite a good visualisation but 31 is 1/30th more yet 8 mph is 8/30ths.

https://www.ukroed.org.uk/stopping-d...new-look-nsac/

which sort of disagrees with the stopping distance calculation.

https://www.f1autocentres.co.uk/news...ping-distances

at 30 its 9 metres and at 40 its 12 metres.

so to drop 1 extra mile leaves you doing 8 miles an hour at 9 metres yet stopping from 40 would cost 3 metres more than stopping from 30.

Travelling at 30 it takes less than a second to travel 12 metres the same for 31 mph.

https://www.timecalculator.net/speed...ime-calculator

Unless they were using electronic means to trigger the emergency stop the thinking time variation would be sufficient to skew the results.

[vetran]

On the M40 I regularly get 70mph Same on the M4 after Reading to Bristol. M1 not so much.

Now if they stopped lorries taking 2 miles to overtake that might help.

Tailgating cameras are needed on all motorways, the majority of accidents are rear end shunts normally with a German car at the back.

[malvolio]

On the M40 I regularly get 70mph Same on the M4 after Reading to Bristol. M1 not so much.

Now if they stopped lorries taking 2 miles to overtake that might help.

Tailgating cameras are needed on all motorways, the majority of accidents are rear end shunts normally with a German car at the back.

There's a sticker on the back of my motorhome - "If you can read this you're driving an Audi"

[d000hg]

On the M40 I regularly get 70mph Same on the M4 after Reading to Bristol. M1 not so much.

Now if they stopped lorries taking 2 miles to overtake that might help.

Tailgating cameras are needed on all motorways, the majority of accidents are rear end shunts normally with a German car at the back.

I wondered if lorries overtake deliberately to take turns giving each other the aero benefit, but Google suggests it's nothing as interesting. I wonder how much of an effect it is. When we have car/lorry 'trains' who can follow each other incredibly closely, it would presumably be non-negligible.

[DoctorStrangelove]

Stopping distance:

https://www.random-science-tools.com...g-distance.htm

Drag vs speed:

https://mechanixillustrated.technica...-aerodynamics/

And the dear old 55mph blanket speed limit of yore that went along with 145 bhp out of 5 litre V8s back in the 1970s.