Not sure where this idea leaves the funding for public transport but it has merit. In Melbourne the train/tram/bus ticketing system works off the premise that having bought a ticket you then have to ‘validate’ it. So, for example, having paid $3.50 for a 2-hour ticket at 10am you validate it and printed along the top it will say ‘expires at midday.’ All good, however the majority of time i’ll only use approx. 20 mins of the two hours. So on exiting the railway station i always leave my ticket, with unused credit, on the shelf of the ticket machine where the coins have to be fed in, as above. I have since discovered that i’m not the only one thinking along these lines with people leaving their tickets in other convenient-benevolent places. Where there’s smoke.