Fourth day of strike action at Yorkshire Ambulance Service
Yorkshire Ambulance Service has urged the public to use the service "wisely" ahead of a fourth strike by paramedics.
Members of the Unite union walked out for five hours from 15:00 GMT in protest against new shift patterns.
The union claims proposed longer shift patterns could lead to staff working for up to 10 hours without a meal break and affect patient safety.
The trust said it continued "to strongly refute" the union's claims about the shift changes.
Unite members took industrial action for a period of 24 hours on 1 February, for four hours on 3 February and for five hours on Friday.
Speaking last week, Terry Cunliffe, Unite regional officer, said: "The latest strikes over elongated shift patterns follow the latest refusal of the Yorkshire Ambulance Service NHS Trust to meet Unite to resolve the dispute."
The union claimed new shift patterns would be "unsafe" for staff and impact on patient care, but the trust has denied this.
David Whiting, chief executive at Yorkshire Ambulance Service NHS Trust, said that less than 2% of the workforce took part in the earlier strikes.
"Industrial action in this form is certainly not in the best interests of patients," he said.
"It is deeply concerning for a trade union representing ambulance service workers to strike without making any concessions to patient safety."
Mr Whiting said the trust had contingency plans in place to deal with the strike but asked the public to call for an ambulance only "when someone has a life-threatening or serious illness or injury."