The posters could run from January
Bendy-buses with the slogan "There's probably no God" could soon be running on the streets of London.
The atheist posters are the idea of the British Humanist Association (BHA) and have been supported by prominent atheist Professor Richard Dawkins.
The BHA planned only to raise £5,500, which was to be matched by Professor Dawkins, but it has now raised more than £36,000 of its own accord.
It aims to have two sets of 30 buses carrying the signs for four weeks.
The complete slogan reads: "There's probably no God. Now stop worrying and enjoy your life."
As the campaign has raised more than anticipated, it will also have posters on the inside of buses as well.
The BHA is also considering extending the campaign to cities including Birmingham, Manchester and Edinburgh.
Professor Dawkins said: "Religion is accustomed to getting a free ride - automatic tax breaks, unearned respect and the right not to be offended, the right to brainwash children.
"Even on the buses, nobody thinks twice when they see a religious slogan plastered across the side.
"This campaign to put alternative slogans on London buses will make people think - and thinking is anathema to religion."
Hanne Stinson, chief executive of the BHA, said: "We see so many posters advertising salvation through Jesus or threatening us with eternal damnation, that I feel sure that a bus advert like this will be welcomed as a breath of fresh air.
"If it raises a smile as well as making people think, so much the better."
But Stephen Green of pressure group Christian Voice said: "Bendy-buses, like atheism, are a danger to the public at large.
"I should be surprised if a quasi-religious advertising campaign like this did not attract graffiti.
"People don't like being preached at. Sometimes it does them good, but they still don't like it."
However the Methodist Church said it thanked Professor Dawkins for encouraging a "continued interest in God".
Spirituality and discipleship officer Rev Jenny Ellis said: "This campaign will be a good thing if it gets people to engage with the deepest questions of life."
She added: "Christianity is for people who aren't afraid to think about life and meaning."
The buses with the slogans will run in Westminster from January.