They’re doing that on the M6 aswell. There’s a newly surfaced section at Lancaster and another at the south side of Carlisle with new concrete barriers.
Grayham:
Surely the M6 roadworks are there to make you take the M6 toll road and cough up for the privelege?Noticed on the M4 they are replacing the central barriers with concrete, why are they doing this? The metal barriers are fine everywhere else, if there’s an accident and its get damaged it’s gonna take weeks fitting a new concrete section in whereas the metal barriers only take a couple of hours.
The concrete barriers are reinforced with high tensile steel cables all the way through and will withstand a massive impact without the need for replacement so in the long run they will last longer than the metal ones which need replacing every time they’re hit, meaning a lane has to be closed both sides for repair work. 
The metal barriers are only good for a car at a moderate speed hitting them at an angle of about 35º, anything heavier than that most of the time flattens them completely.
Also a lot of the roadworks south of J21A are for preparation for “Managed motorways” ie , using the H/S as a live lane during busy periods. this is also going on on the M62 up towards J22 from M/chester.
xamtex:
You want to try M1/M25 at night…they have just started adding an extra lane between 13 and 10…finish date spring 2013!!!
why does it take so long■■?
Yeah I know… 
Paul-H:
Just to be consistent, so is the M3 from J3 to almost J2. Must be the weather or something in the air to bring out all those ‘workmen’
Oh yeah and those god forsaken ‘Average Speed’ cameras, spend more time looking at the speedo than on the road.
Up until a few monthes ago it was Basingstoke to J2 
The Highway Man:
Grayham:
Surely the M6 roadworks are there to make you take the M6 toll road and cough up for the privelege?Noticed on the M4 they are replacing the central barriers with concrete, why are they doing this? The metal barriers are fine everywhere else, if there’s an accident and its get damaged it’s gonna take weeks fitting a new concrete section in whereas the metal barriers only take a couple of hours.
The concrete barriers are reinforced with high tensile steel cables all the way through and will withstand a massive impact without the need for replacement so in the long run they will last longer than the metal ones which need replacing every time they’re hit, meaning a lane has to be closed both sides for repair work.
concrete barrier tests
youtube.com/watch?v=x7TxYWU_Y6I
Try going from kent to the north east overnight at the moment you’ve got M25 j27-26 roadworks,then it’s hit and
miss if the slip road onto the northbound M11 is open then M11 j10-11 closed and as from last night the A1 is shut
northbound at Stamford, all this will put 15-30 mins on your driving time.