Complex sentence: The Luas system has caused much disruption in Dublin, in retrospect many believe an underground would have been a better option, one of the current options being discussed is to upgrade the Luas to a metro system when the metro is being installed.
Split into simpler sentences: The Luas system has caused much disruption in Dublin; in retrospect many believe an underground would have been a better option. One of the current options being discussed is to upgrade the Luas to a metro system when the metro is being installed.