Tried and tested "technology"

Latest figures show the ageing rolling stock on Britain's railways is slowly getting younger, with the average train just over 20 years old.

But it is still a far cry from the sleek future promised by privatisation. So where are all the plush new trains?

Like the Connex carriages at Ashford, much of the fresh stock is sitting untouched and idle. Ironically, putting it into service might create more problems than it would solve.

Performance risk

The trouble is that new trains have teething problems. And at a time when rail operators are trying desperately to claw back their pre-Hatfield performance figures, this sort of rolling stock is just a liability.

Electric v Diesel

In some tests, electric motors in new trains have interfered with signalling, causing a red signal to turn green

Five years ago South West Trains trumpeted a multi-million pound order for 30 new Juniper trains. Twenty-four have so far been delivered, yet on an average day only about 40% of these are in service.

Many are undergoing technical modifications, says a company spokeswoman.

Other examples include:

• Connex's 55 new Electrostar trains, which were delayed because features such as sliding doors, air conditioning and rapid acceleration require more power than current stock
• c2c's delay in deploying 44 new Electrostars because of late delivery and problems with testing
• Trouble with new Class 175 Cordia trains ordered by First Northwestern. Some platforms had to be shaved after it was found the trains were wider than expected. Locos were also withdrawn because brake discs showed excessive wear

For those passengers eagerly awaiting cleaner, more comfortable trains, the unhappy truth is that the older models are more reliable, says James Abbott, editor of Modern Railways.

Reliability curve

"The reliability of a train is rather like a bathtub curve. When it's new it has lots of problems because no one is familiar with how it works," says Mr Abbott.

Train makers need to design to specific track gauges

"As they bed down they become more dependable and in old age they start to go wrong. It's the same with all engineering but with cars, for examples, they are such a mass market product all the testing goes on behind the scenes."

Issues such as track gauge and platform width, mean trains must be tailored to a particular network.

Good lines of communication are needed between the network owner - Railtrack - and individual train manufacturers such as Alstom and Adtranz.

Teething troubles of this sort are not unique to the UK. But a complicating factor here is the procedure for safety clearance of new trains, says Mr Abbott,

Cleared for safety

"In place of British Rail, you now have a contractual matrix of lots of different companies and they are all trying to cover their own backs. It means that everyone now has a good reason not to sign something off."

And then there is the fact that with old trains there is simply less that can go wrong.

"With the slam doors you've got the bog-standard electric traction motor that is based on tried and tested 80-year-old technology. You've got slam doors, toilets that dump contents on the track. There's nothing much to it.

"Now that the new models have retention toilets, electric doors, electric passenger information, the scope for something going wrong is much wider."