More than 300 million journeys have been made on the Elizabeth line since it opened less than two years ago.
London transport commissioner Andy Lord hailed the “staggering achievement”, with up to 4.7 million journeys a week now being made on the £20 billion line.
Transport for London is now investigating whether to retro-fit “busyness indicators” to the train carriages — similar to those on Thameslink trains — to help passengers find a seat.
Mr Lord said: “The Elizabeth line continues to be an incredibly popular service. On December 14, demand reached 770,000 journeys on a single day, and there were 4.7 million journeys made in that same week.
“At the end of January, over 300 million journeys have now been made on the line since it opened in May 2022. I think that is a staggering achievement for what is one of the greatest railways in the world.”
An estimated 38 per cent of passengers using the Elizabeth line are “new” — for example, having chosen it instead of not making the journey or as an alternative to travelling by car.
Work is continuing to improve reliability on the line, in particular on Network Rail-owned tracks west of Paddington where there have been ongoing issues on an almost daily basis.
The line, which extends from Reading and Heathrow in the west to Shenfield and Abbey Wood in the east, also suffered a major failure on January 22 due to a train fault at Farringdon.
Upgrades to the on-board computer software are due to be completed this week, while improvements to the line’s signalling system should be finished by June.
When the first section of the line opened in May 2022 it was about £4 bilion over budget and three-and-a-half years late.
Details of two reports outlining what caused passengers on four Elizabeth line trains to be stranded for hours in the cold and dark, when power lines came down outside Paddington on December 7, are due to emerge next month.
Passengers on the Heathrow Express and a Great Western Railway intercity service were also affected.
Mr Lord said passengers were held on trains for an “unacceptable amount of time” before having to walk on the tracks to get home.
The aim will be to improve the speed at which passengers are evacuated in the event that this happens again, and to improve the poor performance of the track infrastructure.
“Full reports are being finalised on both the root causes of the incident and the operational response,” said Mr Lord.