Pollution and dropping the speed limit.

[ThePinkOne]

I wouldn't be surprised that if you spoke to motorists they'd want the speed limit raising,they'd give any number of reasons for it,but at the bottom of it is they think speed equals shorter journey times when all it does is create 'plugs' of traffic that slow then accelerate causing more pollution without any time gain or even longer journey times.
IMHO speed limits need critical inspection on UK roads and their enforcement needs to be greater including average speed cameras especially on busy motorways and trunk roads such as in the OP.
As for councils I'm with Tykes' ,councils can make some incredibly stupid decisions if it means if it there's a few votes in it for them

It's not just local councils who are daft,the Cameron government when first it came to power spoke about raising the motorway limit to 80mph until it was pointed out to them by someone with a fully operative brain that such a move would actually increase traffic jams and cause a lot more pollution.

I think I read somewhere that on M-ways, you get maximum road capacity at 50mph, which probably explains the way the "smart" m-ways work- 60mph if not too busy, but down to 50mph as traffic volume increases. Although 50mph NEEDS average speed cameras, otherwise the HGVs will (a) dangerously tailgate any vehicle doing under 56mph, (b) you will still get the HGV "elephant races" with the Lane 2 tailgating that will go with that and (c) Mr Toad in the BMW/Audi (etc) will dangerously tailgate in the 3rd lane (so you can get 3 lanes of traffic where dangerous tailgating is the result if people obey the limit). I'm a fan of smart m-ways and speed-restricted sections, but ONLY if they have enough camera enforcement to make it work. When I have to travel long distances on the m-way, I much prefer bimbling along at a steady 55-60 mph, it's much less stressful and my fuel consumption is even more excellent (70mpg+ in a small petrol car).

Taking the topical M4 in South Wales. Contrast the behaviour of vehicles in the 50mph at Port Talbot (average speed cameras all the way through) and that at the "smart" m-way scheme from J28 Tredegar House to J24 Coldra. They only turned the cameras on recently, and there's only 2 in each direction (which the regular users- i.e. most users- get to know the location of very rapidly) so the speed limits are not very effective. Mind you, it is rather a second-rate "smart" scheme with only a handful of overhead gantries and the rest being signs on the side of the road, plus the Welsh Government seems to drop the speed limit down for all sorts of obscure (or apparently non-existant) reasons- thus increasing non-compliance.

TPO

[[XAP]Bob]

So, are all these smart motorways going to help any of our motoring problems? I assume it's about detecting issues then slowing traffic to prevent snarl ups. Do they work in the UK. We're not a considerate driving nation afterall despite the impression a fair few on here give about their driving.

I suspect they help but they're rather scary if you actually keep to the smart-signed speed limit because you'll still have plenty of other motorists racing up behind/past you. I try to plan routes to avoid them at peak times where lower limits are likely to be advertised and Mr "I commute every day and there's usually no reason for the low limit" is likely to be blasting past.

The average speed cameras tend to ensure that everyone runs within a small delta of the speed limit. Those who use GPS a little faster than those relying on wheel sensors, those who reckon there is a 10% leeway going a little faster than those who stick to the limit...

But the overall variance is much much smaller than without them.