Members of the Unite Union on strike at a bus stop on the Lisburn Road in Belfast
Translink workers are planning four further days of strike action in February, trade unions have announced.
In a joint statement, Unite, GMB and Siptu announced the first of these will be on 1 February.
The unions are taking action in a dispute about pay.
Bus and train services have been halted during other strike days in recent months including on 18 January when 16 trade unions across the public sector went on strike.
This followed four days of action by Translink staff in December.
The trade unions have called for the Northern Ireland Secretary Chris Heaton-Harris to release funds to allow Stormont departments to pass on pay awards.
Mr Heaton-Harris has said he has no legal power to release the money himself as it is a devolved matter.
He has promised parties a £3.3bn financial package, including provision for public sector pay, if the Northern Ireland Executive is restored.
It has not met for 23 months as part of the Democratic Unionist Party’s protest against post-Brexit trade rules.
‘No alternative’
On Tuesday, Unite general secretary Sharon Graham said “in the absence of any movement on pay, public transport workers have been left with no alternative but to escalate their strike action with further strikes”.
GMB regional organiser Peter Macklin said the secretary of state’s “behaviour to date to workers, our public services and indeed the public has been nothing short of disgraceful”.
SIPTU regional organiser Niall McNally said the three unions were “seeking to coordinate our action with that of the wider trade union movement to keep the maximum pressure on Chris Heaton-Harris so that we can win for workers and our public services”.
