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To date I've not seen one of these atheist/agnostic adverts, except by Googling them (not sure if m'colleague has?), but with 800 buses nation-wide carrying the advert, they are most certainly out there. They can also be seen on the London Underground.
At the end of last week, a driver in Southampton, working for First, made national headlines when he - of Christian faith - refused to drive a vehicle based at First's depot there that had an atheist advert on the side. Wanting to nip any possible claim of prejudice on the grounds of religion (and the bad publicity this could bring - remember the Stagecoach bus boycott when its chief exec Brian Souter showed his support for Section 28?) in-the-bud, First Southampton has "agreed to do everything it can to accommodate his refusal to drive the vehicles".
First will also be more than aware that the public has no idea that it has nothing to do with the adverts that appear on the sides of its vehicles, being provided and applied by companies such as Viacom. Revenue from this type of advertising on buses provides a fair sum of money for operators. The solution could be for operators to welcoming advertising on their buses but specifying they would not allow advert-carrying statements that could annoy religions.
It could be that First's sympathetic view towards the situation could be the minority view. Initially I suspected that the nation would be behind Ron Heather, the driver - we still live in a country whose main religion is Christianity, after all - but having trawled through the web looking for other papers' online 'take' of the story seems to suggest little sympathy.
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The Southampton bus driver's case is further marred by the chief executive of the British Humanist Association (BHA), Hanne Stinson, who said, "I don't think he should be allowed to refuse. There's no way that the advert on the side of a bus means the driver agrees with it. It's important that people have the right to express their belief." It is the BHA who is behind the so-called atheist adverts on buses.
The Atheist Bus Campaign has its own website (it closes on 14 April 2009), where "freethinkers and atheists" can donate money, and also has a shop that sells its own merchandise.
The bus adverts carefully (deliberately?) carry the word "probably" (There is "probably" no god...). The European press are reporting them as "agnostic adverts"; perhaps they get the real message being portrayed?