If only it were that simple. The London transit system is already at breaking point during peak hours, particularly the Underground, as is demonstrated by the overcrowding, and the ominous "signal failures". It is exhorbitantly expensive and yet people still have to use the Tube - imagine what would happen if you made it free in the condition that it is. I agree with you that public transport should be very very cheap (if not free) but they first need to demonstrate that the system can handle it.