Eighty of the vehicles will be operational by March

On Monday, a state of "special emergency" was declared after the service struggled to cope following a record number of calls.

One paramedic said the vehicles would assist lifting and handling and cut turn around times at hospitals.

Two previous bids to update the fleet have not been entirely successful.

But Wednesday's unveiling comes just two days after a plea was issued for people living in Cardiff and the Vale of Glamorgan to only dial 999 in life-threatening situations.

The state of "special emergency" was downgraded later the same day after call levels returned to normal.

The vehicles have been designed with fast and easy accessibility to equipment and, as you know, seconds do save lives Chief Executive Alan Murray

But it followed a turbulent 12 months for the service, with changes at the top in management, claims of crisis and response targets being missed.

Chief Executive Alan Murray said the mbulances and �55m radio system announced earlier this month marked the trust's determination to improve the service.

One hundred ambulances now in use have outlived their planned service life, but by the end of March 80 of the 119 Mercedes Sprinter 515 vehicles are expected to be on the road.

Previous attempts by the trust to buy new ambulances have not been entirely successful.

In 2002 it bought 30 ambulances but the supplier went out of business before the contract was completed, and those which were delivered were found unsuitable for work in emergencies.

In 2005 it emerged 46 newly converted vehicles were overweight when fully laden with fuel and people and they needed to be altered to make them safe.

The latest ambulances have been paid for by �16m of Welsh Assembly Government funding which will also provide 67 patient care vehicles.

Fleet manager Tony Cowley said:"We believe it to be the best ambulance in service in the UK and we feel sure staff will want to get to grips with it."

Paramedic Osian Roberts, 34, from Llandudno, said the new vehicles were "much roomier" and had automatic gearboxes which would make for a "smoother ride".

'Save lives'

"The biggest thing will be the reduction in the amount of lifting and handling we have to do.

"We'll be able to cut turnaround times at hospitals too because we have our own wheelchair instead of having to hunt round A& E for one," he added.

Mr Murray said: "The vehicles have been designed with fast and easy accessibility to equipment and, as you know, seconds do save lives.

"Our goal is to provide the country with the modern, 21st Century healthcare provider it deserves by giving our staff the tools to deliver that service and this underlines our commitment to doing so."