When city bosses unveiled their clean air zone plan, the predictable first responses from social media ‘experts’ were that it was just a money-making scam.
“Clean air equals cash for the council,” said one.
“Stop targeting motorists for revenue, it’s beyond a joke” said another as accusations abounded in some quarters that it was just a cash strapped council tapping the hard-pressed motorist to prop up its failing finances.
Of course some of those same arguments were from the petrol heads who rail against speed cameras and bus lane enforcement cameras.
But, bearing in mind that no business case for this exists, it seems that the scheme will be lucky to break even - let alone give the city council a surplus.
If it is a resounding success those with polluting vehicles will avoid the city centre entirely, providing zero, or next to zero revenue.
We will assume the council has learned lessons from the 2013 bus lane debacle, that warning signs will be at least adequate, and those driving in will do so with full knowledge of the cost.
Many workers are already priced out by the up to £20 per day cost of parking and those passing through will go round.
There is also a time element - it is in general only petrol cars made before 2006 and diesels before 2015 which are being hit and these will be phased out as people upgrade or scrap their old vehicles.
More will move to cleaner electric engines as they become more affordable and more charging points are installed. Driverless cars could be here in a few years.
New MOT emission rules and proposals to stop licensing higher emission taxis after 2020 will also have an effect.
The potential for revenue is declining all the time.
Even if the council does nothing, pollution from vehicles will tail off over the next decade - but this is too slow to meet the city's 2020 deadline.
So the clean air zone will accelerate the process.
The region's largest bus company National Express West Midlands is replacing old stock with cleaner vehicles and fitting emission capture devices to others.
But it is easy to see how the threat of a £100 per day per vehicle charge will lead them to move the heavier polluting buses to routes serving Coventry or the Black Country, keeping the clean ones in Birmingham.
It is a similar case for the HGV and delivery vehicle operators - larger national companies will ensure, just as they are with the London Low Emission Zone, that the cleaner vehicles serve Birmingham, leaving dirty old trucks delivering elsewhere. It will displace pollution to Wolverhampton, Worcester or Stoke-on-Trent.
And as older cars move from the A38 tunnels to the ring road schools such as the Wisdom Academy, which is next to Lawley Middleway in Nechells may see an increase in pollution.
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This is the reason groups like Friends of the Earth want to see further national restrictions on diesel and petrol cars, and some politicians are calling for the Government to bring forward its plans to phase them out by ten years from 2040 to 2030.
So the opportunities for the council to make money from this scheme are slim at best - the promise to invest any surplus in public transport is, perhaps, empty.
There will be huge set up costs of a network of cameras, signs and new junction layouts as well as the administration of the scheme. Set up costs will run to millions.
Birmingham, along with Nottingham, Derby, Southampton and Leeds who are also introducing clean air zones, is hoping to get Government funding for this, or at least a substantial part of it.
Even then the council will probably be lucky to cover the running costs.