Work will soon be carried out at Hanwell, Iver, Langley and Taplow to ensure all 41 Elizabeth line stations are step-free by the railway's opening in December 2019.
Improvements to Hanwell station will include two new lifts and refurbished entrances and subway.
Making public transport more accessible will help to meet some of the aims of the mayor's draft transport strategy, which seeks to reduce reliance on cars and tackle air pollution.
It hopes to “change the face of travel in London” so that 80% of journeys in the capital are made by public transport, cycling or walking by 2041.
Speaking after the announcement, deputy mayor for Transport Val Shawcross said it's vital our transport networks are accessible to all.
“I’m delighted that four more stations are becoming step-free for the first time,” she said.
“The Elizabeth line is going to transform travel across the capital and it’s only right that every station will have step-free access.
“It’s vital that our transport network is accessible to all and that’s why we’re investing more in making our stations step-free than ever before.”
Paul Maynard, rail and accessibility minister, added: “TfL is making excellent progress to ensure all stations are step-free as part of our investment to revolutionise London’s transport network.
“Through the accessibility action plan, we are committed to further improving the travel experience for people with disabilities, giving them the right to travel independently and with confidence.”
TfL announced earlier this month that it was taking over the running of 11 stations between Acton Main Line and Taplow from December 10.
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