It will reduce pollution, discourage people from driving and liberate the less fortunate in our society.
Today I read that a couple were fined £114 for leaving a train early. The trains are run by private companies but they receive enormous subsidies. Neither national nor local government should subsidise private companies, certainly not these parasites.
I did some costing of this ten years ago; my arithmetic together with my letter to Ken Livingstone can be found here
I had one bloke say it was rubbish but there has been no serious criticism of it, and no refutation.