Ambulance crews have called four more strikes in a long-running dispute over patient safety.
Staff will walk out for five hours on four occasions, starting on Friday.
Members of Unite cite “the continuing refusal of management to hold talks” as the primary reason for the action in the Yorkshire ambulance service.
The first strike is set for Friday, followed by Monday and Saturday, March 29, between 3pm and 8pm on all three days.
There will be a further five-hour stoppage between the same times on Monday March 31.
The crux of the row – lasting more than a year – is the introduction of shift patterns the union says could see staff working 10 hours without a meal break.
Unite says it is only a matter of time before someone is seriously hurt or killed as a result of staff exhaustion.
Calling for an inquiry by the Care Quality Commission, Unite regional officer Terry Cunliffe said: “Our members have shown amazing solidarity, despite the hard line management has continued to take.
"Our members don't take strike action lightly. It has been a last resort.”
The union wants protected meal breaks of 30 minutes after six hours.
A spokesman for Yorkshire Ambulance Service NHS Trust said: “Once again, this will take place without any concessions for the most seriously ill and injured patients and we remain concerned over this type of action.
“We have continued to seek dialogue with Unite through Acas. Our focus will continue to be on safeguarding patient care and minimising disruption.”