The strike is seeing another 48-hour stoppage of services
SIPTU members in Dublin Bus have criticised what they say is "the lack of interest" shown by the Department of Transport and management in trying to resolve a dispute at the company.
The strike will see all services terminate for 48 hours from 9.00pm Wednesday, including Airlink.
More than 400,000 commuters are facing travel disruption as a result.
SIPTU transport organiser Owen Reidy said: "An industrial dispute is always eventually resolved through negotiation. The problem our members are facing in this dispute is that those they need to negotiate with would seem to have gone into hiding.
"In such a situation, I believe it completely fair to squarely place the responsibility for the inconvenience that the public will unfortunately endure tomorrow on those who are unwilling to even attempt to seek a negotiated end to this dispute.
"As always, SIPTU representatives are available at any time to enter into serious negotiations aimed at finding an agreed resolution. Unfortunately, as of now there is no one sitting at the other side of the table."
Dublin Bus has again apologised to customers for the inconvenience and disruption, urging all employees and trade unions not to engage in the planned strike action.
No Dublin Bus routes, sightseeing tours or Airlink services will operate on Thursday and Friday.
Nitelink services will not operate on Friday night or Saturday morning, but will run on Saturday night and Sunday morning.
Dublin Bus accepted a Labour Court recommendation of a pay hike of 8.25% over three years for all employees across the company, calling the increase "fair and reasonable".
It says the request from workers for a 15% pay increase will cost €50m over a three-year period and "seriously undermine our financial stability".
The company says the continued industrial action is costing it in excess of €600,000 each day - which is diminishing its ability to fund the 8.25% recommended by the Labour Court, it claims.
The head of the National Bus and Rail Union (NBRU), Ray Coyne, has hit out at that assessment of the Labour Court recommendation.
"Staff clearly disagree with this assessment, after all they rejected the recommendation across all grades.
"The industry 'norm' to which you refer across public and private sector has one fundamental supporting mechanism, they are supported by agreements from those who work across those specific sectors.
"The absence of an agreement on pay over eight long years, peppered in between with cuts to take home pay has is the main, been the central motivator behind Dublin Bus staff's demand to seek significant pay rise."