There is practically no road you can build which will ever satisfy those criteria, except in quite unusual and curious conditions - I'm sure someone can devise an example if they try hard enough. But rarely. If you have 0 roads and propose to build 1 road, it will fail to satisfy those criteria. If you have 1 road and propose build a second road, it will fail to satisfy those criteria. And, to all intents and purposes, all the way from there to the present road network. Is 0 roads the right number of roads in Wales?The Welsh government said all future roads must pass strict criteria which means they must not increase carbon emissions, they must not increase the number of cars on the road, they must not lead to higher speeds and higher emissions and they must not negatively impact the environment.
So, what about the latest roads that was built in Wales? Like the Heads of the Valleys road? By those criteria, it shouldn't have been built. Should it now be dug up, because it was inconsistent with these road-building criteria? And when they have dug those up, perhaps they should carry on until they have none left. Because practically every single road they have ever built fails to satisfy those criteria.
This is no basis for deciding whether you should build roads or not. It is, rather, a statement that translates to "no roads ever anywhere". It appears to justify a policy, but in fact makes no sense at all. The only purpose of building roads is to allow traffic to go along them. But they have adopted a statement that denies a road the only purpose it should have.
Wales is for the most part a region of relatively uncongested roads, and low population growth. So it can impose a long term freeze on road building at relatively little economic cost. Wales rejected every feasible plan to deal with much its worst road bottleneck - the M4 past Newport. So, if that was their decision in that case, perhaps it is not so hard to decide to reject everything else too. And maybe you can find some way of justifying that, in a way that doesn't suggest that much of the existing network should be dug up. But not with a statement that translates to "no roads ever anywhere."