Trucks are already limited and Euro6 includes eco training driver monitoring systems... So that's not news.
A 10km/h reduction would actually equate to an increase in traffic speeds as road systems are gradually being updated to add traffic lights and roundabouts to slow traffic, likewise building housing estates on the fringes of existing villages and hamlets. The A29 now has as much traffic heading south at 6am as north effectively stopping all overtaking so it has become a 35mph schlep. My 26 mile commute takes ten minutes longer than it used to, except at 3 am and only then by completely ignoring the ridiculously low limits. It was once possible to do it in 30 minutes in rush hour.
Will be commuting to Heathrow at some point which will be fun, but at least I can do that journey in just over an hour. Which makes no sense as it is almost twice the distance.