Alan Kelly (Tipperary North, Labour) | Oireachtas source

We could introduce such a system if we got down to a common fare across Dublin city and the greater Dublin area. That, however, is not going to happen in the short term. We would have to examine the fleet of buses to allow for tag-on and tag-off. The capital requirements would be so substantial that it would not be practical to introduce such a system. The current system is the best solution for Dublin city and the broader area. In addition, a number of substantial enhancements to the Leap card will be announced in the coming weeks and months, which I am sure the House will very much welcome.

See this speech in context