I take it there is no discounted fares on this (like with Oyster)?
Tomorrow, cash fares will increase by an average of 15% whereas Leap Card fares will rise by an average of 5%
http://www.dublinbus.ie/en/Fares--Tickets/Fare-Information/Fares/
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That's an interesting way of doing it, what's wrong with using a touch out system on buses like with Trent Barton's Mango Card in Nottinghamshire?
I would also favour that system and is also used for the Dutch nationwide OV-Chipkaart. Gothenburg has an interesting hybrid system. If you are travelling within the same zone where a flat fare applies, you only need to touch in. If you are travelling outside the zone they you can press a button when you touch in and you have to touch out.
The problem with a touch in touch out system is that people can fare dodge by touching out a long way before they actually get off, so maybe this has put off the authorities in Dublin. Maybe they also don't want complaints from people who forget to touch out. It also requires the reader to always know what the location of the bus is. This is controlled by GPS in most places but maybe Dublin buses aren't suitably equipped.
Needless to say, the Dublin system still is not really integrated as you are still paying for buses and trains separately and even bus to bus transfers are not free. There also appears to be no daily capping like London.