ALMOST half of the new state-of-the-art trains set for the south's railways are on track.

Rail chiefs have revealed that nearly 350 of the planned 742 Desiro trains have been wheeled out on to the South West Trains (SWT) network.

The upgrade is part of the £400m programme to phase out the old slam-door fleet.

The government had originally ordered all slam-door carriages be pulled by the end of this year but train companies are now likely to be given a 12-month extension.

Plans were also hit because of problems upgrading power supplies.

Rail passenger groups have said commuters are delighted with the new trains and operators said they had received good feedback.

Tim Nicholson, chairman of the Rail Passengers' Committee for Southern England, said the new trains had been welcomed.

He said: "There's a huge difference and people do like them. There have been small snags, like toilets overflowing occasionally, but the big things people are saying is that the trains are a lot more comfortable."

SWT managing director Andrew Haines said: "We are getting really good feedback from our passengers about the comfort levels and facilities of the new Desiro trains, which are replacing slam-doors across our network."

SWT's new Desiro fleet, which features sophisticated electronics, braking systems and air conditioning, was announced as the winner in the Rolling Stock Excellence of the Year category at the HSBC Rail Business Awards earlier this year.

As previously reported in the Daily Echo, however, the new trains are only half as reliable as the 50-year-old rolling stock they are replacing. The older trains could travel up to 120,000 miles without a breakdown while the Desiro fleet might run for only 60,000 miles before experiencing problems.