A top transport official has admitted that the original estimate of 21 minutes for the Luas Cross City journey was overly optimistic.
The Oireachtas Transport Committee is hearing from officials on why Dublin's traffic problems are so bad.
It was announced yesterday that 10 more bus routes would be diverted away from College Green in a bid to ease the gridlock.
Cormac O'Rourke from Transport Infrastructure Ireland says they couldn't have predicted the "issues with motorists behaviour" and the "temporary 10km/h speed limit imposed by the commission for railway regulation".