Simplify the following text for a Grade 10 native English-speaking person.
Original: TfL plans that by 2020 there should be a network of over 100 fully accessible stations , consisting of those recently built or rebuilt , and a handful of suburban stations that happen to have level access , along with selected ` key stations ' , which will be rebuilt . These key stations have been chosen due to high usage , interchange potential , and geographic spread , so that up to 75 % of journeys will be achievable step-free .
Simplified: Transport for London plan to have a network of over 100 fully accessible stations by 2020 , which means that 75 % of Tube journeys can be made with step-free access .