I see that some stretches of the M4 and also some A roads are to have a permanant 50mph speed limit 50mph to cut down on emisions. Dont know if this is a good idea. My cars gear change from 5th to 6th is at 50mph so most of the time the engine would be running at higher revs producing more emisions than if i was driving at say 55mph in 6th. Any thoughts I could be wrong.
