We are already maintaining the trunk road network. Save at the margins and some fairly anaemic expansion, the emissions aren't getting worse.No one who claims that HS2 would be an environmental disaster have said anything about the impact of maintaining the truck road network.
If HS2 is environmentally too costly then why is nothing being said about reducing the emissions from the maintenance of the road network, with consideration being given to closing some roads?
HS2 on the other hand generates something like 30% completely new trips. It is back to the old days of predict and provide. Had we carried on with that for trunk roads our cities would be ringed with flyovers and there would be at least two proper motorways to Scotland not to mention the M303.