Originally Posted by invisible

/engineer mode on/
I think requirement needs to be defined more strictly, otherwise there are a lot of public transport in different part of the world which is entirely free: shuttle buses in National Parks for example, above mentioned Staten island ferry. Or sky lift at sky resorts - it is public transport, is not it? My personal example - to promote visit in local National Parks government in country of Georgia couple years ago during summer time was running free day buses from the capital - especially whole appx 150-200mile day trip with free transportation.

I'd rather define requirements differently: cheapest regularly scheduled, non-promotional, not a specific purpose (shuttle buses, sky lifts, ferry to a specific place, etc) public transport.

/engineer mode off/

With the above requirement public transport in former Soviet Union was dirt cheap. Bus and Metro (underground rail) were 5 kopeks (0.05 rubles) per ride on unlimited distance, trolleybuses - 4k and tramway - 3k. Official exchange rate was like 0.7rubles=$1 which translates to like 8c per ride for bus/metro. Unofficial exchange rate was several times less.