Get a grip of road use by the simple expediant of providing compeous, high quality and FREE public transport.
Esp in the cities and towns. Elecric trams and busses, pref of the sor tlike Sarajevo has (you know, the Sarajevo that was reduced to the stoneage by a major civil war no too long ago).
They are electric and drive under two power cables, when they need to go off the grid, they have a petrol engine and batteries.
With a bus every 5 - 30 minutes, maybe every hour out of the urban sprawl, road use could fall.
Likewise a german style approach to bicycles, proper lanes, with priorty to the bikes (infuriating in a car I know).
Free use for inner city-town busses-trams-trains. Cheap as chips rail travel. ability to place cars ON trains from Eniburgh etc.
More freight ON trains and canals.
All of a sudden the roads are not as requierd as once thought.
Some of the canals and older rail tracks will need work but that is lucky for us.
We have copious doleys, prisoners and community service people to lend a hand.