They're almost 30 years old yet the outdated trains on the Thameslink line, which runs from Bedford through Hertfordshire and into London, carrying tens of thousands of commuters every day.
Poor seating and a lack of air conditioning on much of its stock has meant the line has come under criticism from passengers.
Now though there could be some light at the end of the tunnel with 29 new trains appearing on the route from December.
The first of a new fleet 116 trains, the Class 387/1s, will begin going into service on trials during December and the New Year. Govia Thameslink Railway (GTR) says they will transform Bedford to Brighton services for Thameslink passengers.
The new carriages will begin to replace the 27-year-old Class 319 trains currently running on the line.
The trains are built in Britain by Bombardier and feature:
- Two-by-two seating
- The latest automated on-board service information
- Improved facilities for people with disabilities
The Thameslink line one of the busiest rail routes in the country and the only mainline train service to currently cross the capital joining Bedford to Brighton.
It runs 140 miles through 68 stations and links Luton and Gatwick airports.
The Class 387 trains are the latest version of Bombardier Transportation's Electrostar.
The 387/1s will be steadily rolled out on Bedford to Brighton services so that in May virtually every train on this service group will be an Electrostar.
They will remain in service into 2016 when, from the spring, an even newer fleet of next-generation Class 700 trains will be steadily introduced as part of the government-sponsored Thameslink Programme, with more carriages for many longer services and, from 2018, more frequent services on parts of the route.
The Electrostar trains being tested at a depot in Bletchley near Milton Keynes are built in Britain with the aim of addressing overcrowding, reliability and comfort issues.
Govia Thameslink Railway which recently took over the franchise from First Capital Connect says it has big plans for its cross-London services. Eventually trains will run from Peterborough and Cambridge will run direct to the south coast.
As part of redevelopment work along the line there will still be disruption. From 20 December and for the next three years no Thameslink trains from Bedford will serve London Bridge while the station is rebuilt.
The station is the fourth busiest in the country handling around 50 million passengers a year and is being re-designed to cope with up to 18 Thameslink trains an hour in each direction.
Click below to watch a report on the new train carriages from ITV News Anglia's Russell Hookey