...apparently 
http://www.timesonline.co.uk/tol/news/environment/article6870115.ece
Seems the committee on climate change are a little late latching onto this report done in 2005: -
http://www.transportenvironment.org/Publications/prep_hand_out/lid:391
Traffic smoothing is the way forward, stop the motorway "lunging" and you'll reduce CO2 output.
Surely there's more ways to smooth the traffic than simply to slow everyone down to a crawl?

http://www.timesonline.co.uk/tol/news/environment/article6870115.ece
Seems the committee on climate change are a little late latching onto this report done in 2005: -
http://www.transportenvironment.org/Publications/prep_hand_out/lid:391
Traffic smoothing is the way forward, stop the motorway "lunging" and you'll reduce CO2 output.
Surely there's more ways to smooth the traffic than simply to slow everyone down to a crawl?