It sounds interesting but if the supply of the coin is limited and being used to pay for rides the total value of the coin would not rise as much. Unless later on fractions of a Duber coin could pay for a ride. Would like to see a bit more details but I could see something like this working.
Yes, the ride would be set in dollars. It might cost 1 duber to pay for a ride at first, but then later on it might cost .25 duber, all other things being equal.