450 Yorkshire Ambulance workers are walking out in a row over cutbacks and changes to the service. Paramedics and other ambulance staff are on strike for 24 hours.
Ambulance workers are to stage a 24-hour strike in a long-running row over issues including cuts.
Unite said its 450 members in the Yorkshire service, including paramedics and other staff, will walk out on 2 April and ban overtime from 26 March.
The union warned that further strikes could be held.
Unite said the Yorkshire Ambulance Service NHS Trust had derecognised the union after it raised concerns about patient safety over plans to make £46 million of savings over the next five years.
Union members voted by 61% in favour of strikes and 83% for other forms of industrial action.
Injury and incidents related to alcohol is costing the economy £9 million in Ambulance call-outs.
A woman was seriously injured when her car collided with a tree on the A1 in North Yorkshire this morning.
The 27-year-old's car aquaplaned before leaving the road and hitting the tree just south of Catterick.
The road was closed for several hours before it re-opened.