More trains are set to stop at Shepherd's Bush Station near Westfield from next year.
Currently just four trains an hour stop at the new Shepherd's Bush rail station at Westfield shopping centre but from early summer that will double.
Half of these trains each hour will continue west to Stratford from May 2010, allowing better connections to the main 2012 Olympic and Paralympic Games Park. The rest will terminate at Willesden Junction.
Hammersmith and Fulham councillor Nicholas Botterill said: "Residents have had to put up with cattle-class trains for too long and rush-hour crowding is expected to increase, especially on lines into London.
"The announcement of extra overground trains will be very welcome for local rail passengers and the increased capacity cannot come too soon."
The upgrade is part of Boris Johnson's £326 million upgrade of overground rail services in London. Around £20 million of that is being spent in Hammersmith and Fulham.
Network Rail engineers will also upgrade more than 200 signals, renew four-and-a-half miles of track and 69 sets of points, lengthen 30 platforms Ð including Willesden Junction - and improve seven stations across the capital's four overground lines by 2012.
At the same time, Transport for London (TfL) is upgrading CCTV, PA, lighting and passenger information screens, providing new signs, undertaking general refurbishment and installing new lifts at some locations.