I drove down the M1 in November from the M6. I do not think I hit 60 mph. What about variable speed limits where necessary?

Variable speed limits often cause jams as they reduce the speed limit too much too quickly. It causes a consitina effect. I've seen it on the M25 loads of times.

They should up the limit to 80, not drop it to 60 IMO.

Plus I drive a lot between 28 and 31, so that would piss me right off!

That's where it narrows down to three lanes again. Great, the four lane stretch from 25 to 28 will serve admirably as a bloody carpark.

They don't have a bloody clue - the A38 approach to M1 J28 is terribly congested at peak times, as is the A629 approach to Junc 29 (though less so). This will make the situation worse.

So two things will happen because of this.

1. The people who currently drive at 70mph will start driving at 60mph.

2. The people who drive at 90+mph will still drive at 90+mph.

This greater difference of speed will create shorter reaction times for the fast drivers and increase risk of accidents.

Plus, it's a [LIFTED] waste of money. Seriously, are they giving a reason for doing this?!

Oh, also, my car gets much better mileage at 70mph than it does at 60mph.

In fact it's something like 60% more efficient.

Maybe it's to whip up a minor storm and draw attention away from something else.

/tinfoil hat

Over here the motorway system has always had speed limits down to as load as 50mph. Sometimes because of tight corners, other times for traffic flow and in some cases to reduce road noise, such stretches are marked as Lärmschutz, which is basically noise protection. Many stretches than run past the suburbs of a city are set to 60 at night, some all the tine.

I suspect that the drag co-efficient which starts to become a bigger factor at 70mph would probably limit any further efficiencies.

Yeah, the sweet spot for me is about 70-75 mph (on my car's speedometer which is actually just under 70mph when measured on my satnav).

Any faster than that and it starts to drop. Any slower and it drops too (for sustained speed, obviously for the initial drop the mileage increases).

I suspect that the improvements up to 70 are down to the engine efficiency and being in the right gear. Much below that and you might be in the wrong gear for maximum engine efficiency.

Anything above 70 and my car starts to drink fuel. It really needs a 6th gear.

It's just the way they're designed. My car is better at 75-80mph than 70mph for fuel economy but that's down to it being European so is designed for maximum efficiency at 100-120kmph

It's being blamed on EU air pollution regulations IIRC. The proposed stretches are closer to residential areas and the levels of NOx in those areas can exceed EU limits at certain times of the day.

I am glad that the EU do regulate our environment since our government do not care about it. There are issues of PM10's which are really small particles that could be very hazardous to health.