While i see your point. I think once AWPR opens we'll see a heavy reduction in traffic and pollution. I do think restricting many streets in the city centre is the only logical answer. It's just unrealistic and wasteful to have a whole fleet of buses Euro 6 compliant by X date.
As i say, putting restrictions on buses should be the last resort.
Regarding car use in Aberdeen, the council here are utterly useless when it comes to bus priority, which is part of the reason why cars are so popular. Most car users deem the bus too slow as it gets stuck in the many bottlenecks around the city that have poor bus priority. North Anderson Drive N-bound is a great example. As is the whole 8 or so mile route from Culter in to the city.
I would think cars are so popular not because the bus is slower, because generally speaking if your using the same roads as a bus your caught in that same traffic, I personally use my car because its convenient to me despite the extra cost of fuel, but I would only use my car locally in a small village etc, but If I visit town I always take the bus, point being that many people will use there cars out of one sole reason, that being convenience, many people nowadays will have access to a bus to there major city within reasonable jounreys time for work and leasure etc
I would like to think that its not the main reason but kinda of a sub-reason that many councils across the whole country don’t move more quickly to halt car congestion is with the biggest regards to our cities making there revenues and bringing in shoppers through people driving to there local city, many a times I see one person per car at rush hour!
Out of fear of reducing that appeal of car use, its whats bring money to our high streets, the public convenience of a car does that, it is a difficult balancing act, although there is reason to believe many could actually save money taking a bus!