60 MPH Limit on Motorways

[StanC]

Originally Posted by Dippydog

There have been several fuel "crises" the last I think was '74 or 5 when it was mooted that fuel rationing was a possibility-I still have the [unused as the rationing never took place]ration book issued for the MkIII Zephyr I owned at the time.I'd have thought pollution levels more a by product of traffic volume rather than speed?

Speed does affect pollution levels. Even with modern bodywork streamlining the energy expenditure in overcoming air resistance is roughly proportional to the square of a vehicle's speed. Cruising along on the level at a steady speed with no air resistance would take very little energy. In the real world there is air resistance, of course, and this accounts for much of the fuel consumption when cruising. Travelling at 70 mph creates a third more air resistance of travelling at 60 mph and almost double the air resistance of travelling at 50 mph. Hence, slowing the traffic results in individual vehicles having better fuel consumption, with correspondingly lower emissions.

Thank you for reminding me about the 1974 oil crisis. The same reasoning applied then - the 50 mph speed limit was intended to reduce the overall fuel consumption of the nation and conserve oil.

Stan.

[biggbn]

I would have no problem with lower limits whatsoever.

[DaveNP]

Overall I agree that lower speeds help reduce fuel consumption, as a truck driver I get through a lot of fuel but I do know that if I can set the cruise control to 50 or 53 instead of the flat out 56 I can improve the fuel economy from 10mpg to 12 or 13mpg, whilst I am driving a large basically rectangular heavy thing, that saving is down to drag and even a super slippy car design will benefit from reducing the top speed.
Where I do have a problem is areas like the M4 through Newport in South Wale where they impose a 'variable' 50 mph limit 24 hours a day with a message about pollution, the problem is that in the truck I then have to ride down the hill using the exhaust and service brakes to keep the speed down and then have to hit the accelerator to get up the next hill instead of letting the truck build up speed and inertia downhill to carry me some way up the next hill without using the accelerator.

(And yes I've still got the ration coupons for the Mini that was my first car, albeit my dad owned it at the time)

[GrantV50]

On short stretches, we should be looking at increasing to 100MPH. Modern cars are capable of this speed, and braking from this speed.

[Bashy]

Originally Posted by GrantV50

On short stretches, we should be looking at increasing to 100MPH. Modern cars are capable of this speed, and braking from this speed.

Whilst that maybe true, not all have decent brakes, take mine recently before I changed them, whilst pads and discs in the front were easily OK by a large margin, any heavy breaking resulted in little stopping power until they cooled somewhat, I'm not even confident they would have been proficient from 100mph.

Dont get me wrong, I would be all for an increase in speed, its just your argument for the proposal is flawed

[DaveNP]

And unfortunately the MOT standard for brakes hasn't kept pace with modern speed capabilities, in good condition modern brakes are much better than the MOT standard, but do we trust everyone to maintain their car beyond the minimum?

[Welton]

Originally Posted by DaveNP

if I can set the cruise control to 50 or 53 instead of the flat out 56 I can improve the fuel economy from 10mpg to 12 or 13mpg, whilst I am driving a large basically rectangular heavy thing, that saving is down to drag and even a super slippy car design will benefit from reducing the top speed.

Hi Dave, I'm the guy that slip-streams you every day on the M1, I'm getting record MPG's thanks but can you speed up a bit please?

[AndyJudge]

getting quite fed up with the constant persecution of the motorist & sticking lower limits on everyone to ease pollution etc.

Simple way to reduce pollution is to get cars off the roads by moving more freight by rail & making the use of public transport to move people cheaper & more convenient.

[biggbn]

Originally Posted by AndyJudge

getting quite fed up with the constant persecution of the motorist & sticking lower limits on everyone to ease pollution etc.

Simple way to reduce pollution is to get cars off the roads by moving more freight by rail & making the use of public transport to move people cheaper & more convenient.

or do both?

[DaveNP]

Originally Posted by Welton

Hi Dave, I'm the guy that slip-streams you every day on the M1, I'm getting record MPG's thanks but can you speed up a bit please?

LOL Despite the MK location I'm not on the M1 that often, but the tongue in cheek remark brings up the idea of slipstreaming, which actually is more efficient for both the slipstreamer and the on being slipstreamed, and then we get into the tech solution of forming virtual trains of trucks linked electronically, on the one hand it should save fuel, but I don't want to be in the cab in the middle.

Originally Posted by AndyJudge

...Simple way to reduce pollution is to get cars off the roads by moving more freight by rail & making the use of public transport to move people cheaper & more convenient.

In over 30 years in road transport the only times I've come across 'moving freight to rail' for journeys within the UK it has been a politically motivated thing and quickly becomes complicated, involving trucks running less than efficiently moving that freight to and from the railheads just to get environmental brownie points. Rail is great for long distance which is why they've recently started up a China to Europe railfreight service.