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Highways England are reportedly introducing a trial to see the effect on pollution of reducing Motorway speed limits to 60 MPH.

The report originally in the Times is repeated in many more accessible places such as here

Interesting quote, laying the blame squarely on ICE and SUVs.

‘Ultimately the air-quality challenge will be solved “at the tailpipe” by vehicle manufacturers and changes in vehicle use.
People may recall that the original speed limit on Motorways were introduced on a temporary basis to cut emissions in 1973.

As usual there is no mention of reducing the speed of lorries who generally drive at the limit rather than 5% below because of inaccurate speedometers in cars.
 

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Seems odd and strangely incompatible with the desire to move away from petrol diesel by 2035 or 2032 if they can speed things up. In theory by 2030 pollution levels should have dropped dramatically as people move to EVs in anticipation of 2032/2035. Will they then increase the road speed again? I'm an optimist so it doesn't make sense to put in place a measure that might need to be revered.i. 10 years.
 

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Good God, I hope they don't reduce HGV speed, it takes a bloody age to get anywhere as it is. In fact they've just (in the last 5 years) increased our speed on A roads from 40 to 50mph. Our limiters run at 90km/h which is 56mph, as you probably know, so if punter-traffic was limited to 60 you would still be easily able to overtake and get past, assuming that is you were prepared to drive at an actual 60.
With my EV hat on, it would be quite nice if the emissions related speed limits were only applied to vehicles with an exhaust pipe. With my HGV operators hat on, I'd say that the mandatory speed limiter fitted to HGVs is a real driver aid - once you accept that it is impossible to circumvent, it's quite a relaxing speed to drive at.
 

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God no. It's bad enough now trying to get anywhere at a decent speed as it is. As an EV driver why the bloody hell should I have to dawdle along for emission related speed limits? There is one of the A55, shouldn't apply to any EVs. Make those producing the emissions slow down.

Irony is it will probably make pollution worse as it will take even longer for vehicles to get through an area :rolleyes:
 

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To reduce emissions it would be a good idea to limit all lanes except the right lane to 60mph and make the right lane of a motorway full EV only, with a limit of 80mph. Overhead gantries would show the limits and use with cameras and ANPR to monitor it. This would also have the added benefit of probably persuading a significant rise in EV uptake in areas where there are congestion.
 

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I don't know the mathematics of these types of ideas, but lowering the speed limit means the trip will take longer and the engine obviously will be running for longer.
 

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It might actually increase average travel speeds.

It is everyone trying to drive at varying excessive speeds that causes traffic flow discontinuities and ultimately 'phantom obstructions'. If one adds in all those incidents too, one's average trip speed might actually increase.

This is because of the traffic density that far exceeds the levels that the motorways were designed for.

I recall a long period of motorway traffic works on my commute, it had been 70 (normal) and always congested, then dropped to 50 (but all lanes) and the traffic flowed freely. Once they removed the limit, immediately got traffic congestion again and journey time went back up again.

This is the idea of the variable speed limits.

The opportunity to 'tune' the system would be good, like higher speeds for BEVs, certain times of day (air 'pollution' is no issue at night if it can disperse before rush hour/daylight), etc..
 

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I don't know the mathematics of these types of ideas, but lowering the speed limit means the trip will take longer and the engine obviously will be running for longer.
Yes but it will be more efficient at those lower speeds. Big difference in emissions between 50 and 70. Don't think its linear. Mpg drops dramatically between 70 and 80 but not between 50 and 60 for instance.
 

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God no. It's bad enough now trying to get anywhere at a decent speed as it is. As an EV driver why the bloody hell should I have to dawdle along for emission related speed limits? There is one of the A55, shouldn't apply to any EVs. Make those producing the emissions slow down.

Irony is it will probably make pollution worse as it will take even longer for vehicles to get through an area :rolleyes:
I live within 5 miles of my quickest junction onto the A55 in North Wales and now there is now at least two sections of this route that has speed restrictions of 50 Mph imposed to reduce the level emissions.
Both of these areas have average speed camera’s monitoring them.
One section even has three lanes and drivers, once seeing this make for the outside lane in the belief it is a national 70 Mph speed limit due to the three lanes !.
Do they not wonder why the rest of the traffic is travelling at a much slower speed than them ?.
Strangely enough, the camera in the car picks up on the newer 50 Mph restriction sign okay, but when leaving the zone it still believes we should still be travelling at 50 Mph and bongs and flashes to indicate that we are travelling to fast.
What I see constantly, when travelling at the permitted speed of 50 Mph, lorries are wanting to push you along and travelling WAY to close and not maintaining a safe distance to stop !.
They don’t want to overtake, but don’t want to slow down either.
They want to edge the very limit of the 50 Mph limit and you are in there way.
On a down hill section, they are almost in the back seat of the car !.
Very disconcerting when we have both grand children in the car.
Purely on a technicality, can you be prosecuted for travelling above the speed limit in a section of road that has had its speed limit reduced primarily on the grounds of increased emissions, in a car that is producing NO emissions at all ?.
I bet somebody could try contesting the law with an expensive barrister or two.
Food for thought ?.
 

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It might actually increase average travel speeds.

It is everyone trying to drive at varying excessive speeds that causes traffic flow discontinuities and ultimately 'phantom obstructions'. If one adds in all those incidents too, one's average trip speed might actually increase.

This is because of the traffic density that far exceeds the levels that the motorways were designed for.

I recall a long period of motorway traffic works on my commute, it had been 70 (normal) and always congested, then dropped to 50 (but all lanes) and the traffic flowed freely. Once they removed the limit, immediately got traffic congestion again and journey time went back up again.

This is the idea of the variable speed limits.

The opportunity to 'tune' the system would be good, like higher speeds for BEVs, certain times of day (air 'pollution' is no issue at night if it can disperse before rush hour/daylight), etc..
I used to drive round the M25 regularly. The improvement in traffic flow when the variable speed limits were introduced was really obvious.
 

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I like the idea of the fast lane for EV only And bus lane access.

OT: A colleague tells me that the car manufacturers are making nothing on EVs and they're really expensive.


Sent from my iPhone using Tapatalk
 

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Obviously with "empty" motorways like M6 north of Lakes being able to barrel along at 80 reduces travelling time but I suspect @donald is absolutely right with busier roads flowing better at lower speeds.

It's like laminar vs turbulent flow in fluid dynamics with the cars being the particles.
 

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EVs and ICEs are much more energy efficient at 60mph compared to 70 or above.

In reality for many journeys the difference in travel time will be a few minutes. Surely no issue for patient EV drivers who are happy to sit at a charger for 45 minutes. Maybe someone has some real numbers to do the maths:

Scenario: long journey of which 50 miles the roads are clear enough to actually allow travel at 70 mph = 43 mins
now at 60mph = 50 mins, diff 7 mins

Using made up m/kwh numbers - at 70mph efficiency is 3miles/kwh, at 60mph efficiency is 3.5miles/kwh, over 50 miles this would save 3kwh

Time saved charging at a 50kwh rapid = 4 mins.

:cool:
 

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Over lockdown, every single town and village in my area has gone from 30 to 20mph pretty much overnight. Even some 60 to 40/50mph. Can't see major routes ever going above 70mph. The trend is pretty clear.
 
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Discussion Starter #18
With my HGV operators hat on, I'd say that the mandatory speed limiter fitted to HGVs is a real driver aid - once you accept that it is impossible to circumvent, it's quite a relaxing speed to drive at.
Near me are a couple of relatively steep sections of motorway. When travelling at a real 60 (verified by Sat Nav and 67 indicated) on cruise control down the hills I am overtaken by the majority of lorries and all coaches. I've no idea of how that's possible with the mandatory speed limiter, but it happens every time I commute. :unsure:
 

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Coasting.
The tacho warns of overspeed and it is recorded but i have never heard of drivers being picked up on it as an infringement.
 

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People may recall that the original speed limit on Motorways were introduced on a temporary basis to cut emissions in 1973
That is not true, the speed limit on motorways was reduced to 70mph as a trial in 1965 to reduce accidents. The trial was then extended and made permanent in 1967.

In 1973 the national speed limit was reduced to 50mph on all roads, the 70mph limit was restored on motorways in March '74.

Speeds on single and dual carriageways were restored to 70 later in '74 but then single carriageways were reduced again in '76
 
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