While the London Underground has been made more accessible in recent years (more than 60 stations out of 270 are now step-less between the street and the platforms), many Tube stations still present challenges for the disabled due to gaps between the platform and the carriage door.

BBC: London for disabled visitors

When the passengers for D301 reached the platform, they encountered a vehicle that looked less like a train than a wingless jet: a tube of aluminum alloy, a quarter of a mile from end to end, containing sixteen carriages, painted in high-gloss white with blue racing stripes.

NEWYORKER: Boss Rail