Three ambulances are being used to care for patients at a Swansea hospital to help free up other paramedics.
The vehicles are stationed outside Morriston Hospital's emergency department, and the agency staff who man them don't go out on calls.
Instead they receive patients brought in by other ambulance crews who are well enough to be transferred but face delays in being admitted to the hospital.
It means those other ambulance crews are then able to respond to respond to the next emergency quicker.
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The Welsh Ambulance Service Trust (WAST) initiative began on November 15, and may be rolled out to a hospital in Cwmbran.
Ambulance response times and accident and emergency performance figures in Wales have deteriorated in recent months.
During October, the ambulance service only attended 50% of red calls - where a life is at immediate risk - within eight minutes on average. The figure was lower in the Swansea Bay University Health Board area, which covers Swansea and Neath Port Talbot.
Lee Brooks, WAST director of operations, said hospital handover delays remained "a serious and long-standing issue" affecting ambulance services across the UK.
Mr Brooks said long-term solutions were needed but that it would be "a dereliction of our duty" not to implement short-term ones like at Morriston Hospital as winter pressures intensified.
"The Morriston Hospital initiative means there are three fully-equipped ambulance vehicles ready to receive patients, each of whom will have one-to-one care by healthcare professionals hired by the trust," he said.
"It means that our crews, if it’s safe and clinically appropriate to do so, can transfer their patient to one of these vehicles and then be available to respond to another patient in the community."
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The Local Democracy Reporting Service put a claim to WAST that the agency staff in the stationary ambulances were on £50 per hour.
It did not comment on this figure, but said agency working was not new to the NHS in Wales, that hourly pay rate was a matter for the individual agencies, and that the need was pressing.
WAST said it will recover the cost of the initiative, which could run until the end of March, from additional funding made available by the Welsh Government.
A Swansea Bay University Health Board spokesman said: "As a health board we are fully committed to improve ambulance turnaround times and we are jointly working with WAST colleagues on a number of initiatives to facilitate more timely release of ambulances and mitigate the risk in the community."
WAST is also discussing the potential of using St John Ambulance Cymru vehicles to care for incoming patients at The Grange University Hospital, Cwmbran, and may roll the scheme out further.
Swansea Council opposition leader, Councillor Chris Holley, said ambulance handover delays happened every winter, and that more trained paramedics were needed.
"And maybe the ambulance service should not be an all-Wales trust and be looked at more on a regional basis," he said.
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