So this GLA study claims that parents have accessibility problems, however it doesn't take into account the adjustments they could make to make their journeys easier on public transport by buying a smaller buggy or dare say it, FOLD them up and place in the luggage rack where it's practical to do so.
Clearly we've evolved to where parents can use buggies on most forms of public transport, however it comes with common sense, something which is lacking from both some parents and the bus companies who either enforce the rules too tightly, drive past parents at bus stops or are too lenient by letting on too many buggies who then block passageways.