Visualizing catalyst activity in Fluid Catalytic Cracking
EMBARQ report points to need to reduce Vehicle Miles Traveled per capita in the US to meet emission and oil consumption targets; “sustainable VMT”

UK DfT to launch consultation on increasing highway speed limit to 80 mph

UK Transport Secretary Philip Hammond has announced a consultation on increasing the motorway speed limit in England and Wales to 80 mph (129 km/h). Hammond said the current limit of 70 mph (113 km/h) is out of date and that the higher limit would give the economy a boost.

The proposal was immediately criticized by environmental and safety campaigners who said it would lead to higher carbon emissions and more road accidents.

Hammond stated that the current limit was out of date due to “huge advances in safety and motoring technology” and that England and Wales’ roads should be the arteries of a healthy economy, stating: “Increasing the motorway speed limit to 80 mph would generate economic benefits of hundreds of millions of pounds through shorter journey times”. The consultation will begin later this year, with a view to raising the speed limit in 2013.

In a recent Parliamentary answer to a House of Lord’s Question, Lord Shutt of Greetland said on behalf of the Government that CO2 emissions increase by around 14% for a vehicle driving at a steady 80 mph compared with a steady 70 mph.



On clean electrified vehicles should be allowed to travel at 80+ mph.

Keith Ruddell

The petroleum industry profits must be down.


How can certain pressure groups of an "alternative persuation" criticise the proposals to raise the 80 mph speed limit on the grounds of increased fuel use when they're quite happy for authorites to introduce designer congestion measures elsewhere which has worse effects?

I'm talking about the politically-led (not safety in most cases) new realist 'right-on' tactics of reducing road space, installing extra traffic lights, unsightly acres of white lining and hatching, chicanes, humps, bollards and so on which make streets less attractive for walking and cycling, let alone driving. Such measures have so far had the effect of REDUCING traffic whilst INCREASING congestion in main cities and hence increasing overall fuel consumption.

Add the proposals to carpet urban areas with 20 mph speed limits, which will ALSO INCREASE fuel consumption. I can understand the logic behind 20mph zones on residential streets and I agree with them if they are needed on safety grounds. But a politically-correct blanket based approch is hypocritical given the effects on fuel consumption.

The 80 mph limit is appropriate for the more quieter stretches of motorways. Why? This is based on the 85th percentile speed - the speed at which most traffic will travel, assuming that NO limit was in place. In other words 85% of the traffic is likely to travel no more than 80 mph, as it's the natural speed for a motorway. This is why most other European countrys have 80 mph limits. Plus 80 mph will be a limit, not a target, giving drivers the freedom still to decide whether to drive at 55, 65, 70 or even 80 mph. When traffic does builds up, it tends to find a more natural slower speed. For me I tend to pick a much lower speed on busy stretches to smooth out the flow and avoid some of the typical braking waves and phantom jams that can happen on busy / overloaded stretches.

Thomas Lankester

I am not interested in pressure group attitudes or linking different measures into some agenda package that they are supposed to have.

But the basic physics is that the force of aerodynamic drag increases as the square of the velocity (e.g. In this case it translates into a 30% increase in the drag force by increasing from 70-80mph. That is not something I am going to support from a UK balance of payments, energy independence or CO2 emissions perceptive. I believe that this was the reasoning behind the 50mph national speed limit imposed during the '70s oil crisis.

The point about the 85 percentile of drivers wanting to travel at 80mph is also based on current driving experience, EU speed limits and vehicle capabilities. When motorways first came in the 85 percentile speed was a lot lower and in future it is likely to rise, if allowed. It is the Field of Dreams effect - 'If you build it, they will come'.

That drivers wishing to travel at lower speeds will legally have the freedom to do so is, surely, a specious argument. In practice, if the speed differential between lanes is too great then it gets harder to change lane and the chance of getting 'boxed in' and intimidated increases.

On big open empty motorways that is not a problem but from my experiences on the M3, M4, M20, M26, M40, M25, M23, M5 - that's a bit of a dream!

RE 20mph limits increasing fuel consumption:
I thought that this was due to the operation of the ICE which operates most efficiently at constant revs. Is this really true for EVs though?


Erm Thomas:

You said: "On big open empty motorways that is not a problem but from my experiences on the M3, M4, M20, M26, M40, M25, M23, M5 - that's a bit of a dream!"

and I said before then:

The 80 mph limit is appropriate for the more quieter stretches of motorways

So we agree don't we?

In any case, most traffic already travels at 80. As I also said the increase in drag and it's impact on fuel consumption can be mitigated to some degree by better taller gearing, and the smoother revving, as you [put it of the ICE engine on motorways because. I think people deserve some freedom of choice - if you want to go faster it will cost you more. This logic already exists for people who choose to live in bigger houses (higher bills more CO2) So perhaps we should all get people to live in shoeboxes and tax single people who live in properties that have more than 1 bedroom?

Thomas Lankester

'The 80 mph limit is appropriate for the more quieter stretches of motorways

So we agree don't we?'

No. My points were:
a) good luck with that!
b) if the Motorway stretch is so little used, then not many people will 'benefit', so why bother?

You cannot mitigate the laws of physics. Drag goes up as the square of velocity. We could reduce the drag coefficient of vehicles but then we could do that anyway without a speed limit increase.

Freedom of choice is always in a balance against social responsibility - how much is one person's freedom impinging on others. With the 80mph proposal negatively affecting UK oil imports, CO2 emissions and road safety, at a time of national financial and carbon emissions austerity, the personal freedom to save a few minutes seems whole unjustified.

'So perhaps we should all get people to live in shoeboxes and tax single people who live in properties that have more than 1 bedroom?'
Isn't that what the council tax does? A G band property owner pays more for having a bit of rubbish removed than someone with the same rubbish bin in a band A studio flat. Personal carbon budgets would be fairer.

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