"Probably planning for the extra traffic created by the new runway at Heathrow." It's part of a much larger programme by Highways England to make better use of existing motorway land by converting 3-lanes-plus-hard-shoulder into 4 lanes of 'smart' (formerly 'managed') motorway with variable speed limits. By providing the extra lane when needed and controlling speeds, you get a much smoother flow of traffic which should reduce pollution, which is often increased on the M4 because of stop-start traffic. The problem is that when the first part of the M4 was built in 1961-63 (Slough and Maidenhead by-passes), it had only 2 lanes per carriageway. It was widened on the cheap to 3 lanes around 1970 without widening the bridges, so there are at least 10 bridges on that section without hard shoulders under them. Basically the M4 is unfit for purpose, and has been for 30 years.  Converting it to a managed motorway is good news IMHO. Rima, do you have a reference to any study that quantifies the increase in pollution that you claim?

Entire Thread

Topic	Date Posted	Posted By
Widening of the M4	20/06/15 19:58:00	Rima Jones
Re:Widening of the M4	20/06/15 20:04:00	Will Watson
Re:Re:Widening of the M4	20/06/15 22:19:00	Rima Jones
Re:Re:Re:Widening of the M4	21/06/15 08:09:00	Rima Jones
Re:Re:Widening of the M4	20/06/15 23:35:00	Richard Jennings
Re:Re:Re:Widening of the M4	21/06/15 09:34:00	Elizabeth Jane Daley
Re:Re:Re:Re:Widening of the M4	21/06/15 12:51:00	David McLoughlin
Re:Re:Re:Re:Re:Widening of the M4	21/06/15 13:11:00	Rima Jones
Re:Re:Re:Widening of the M4	21/06/15 20:35:00	Tim Henderson
Re:Re:Re:Re:Widening of the M4	06/09/16 18:14:00	Tim Henderson
Re:Re:Re:Re:Re:Widening of the M4	06/09/16 18:29:00	Viv Griffiths
Re:Re:Re:Re:Re:Re:Widening of the M4	07/09/16 00:07:00	Richard Jennings

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