Bosses at South West Trains insist that passengers will benefit from a £40 million investment into its Class 455 fleet.

The company confirmed that 91 of the trains - which it says are already the most reliable in the UK - will be fitted with new traction equipment that will help to enhance their performance even further.

Over the next three years, existing DC traction systems will be replaced with modern AC traction solutions and these units will be lighter, thus causing less wear and tear on the tracks.

The new trains will be able to travel 15,000 miles between major servicing works - up from 10,000 at the moment.

Christian Roth, fleet director for the South West Trains/Network Rail Alliance, said: "The new traction motors will help us to improve the reliability of these trains for our passengers at the same time as delivering environmental benefits through the reduced electricity supply."

In addition to this, the firm revealed it will be introducing an extra 100 carriages on to its services over the next 20 months, making space for an additional 23,000 peak-time passengers every day.