The design for London's new Routemaster bus has been unveiled, five years after the iconic bus was withdrawn from service. So how do the two compare?
For a start, there is a big size difference.
The new bus is much bigger than the the old one, says one of the UK's leading bus designers, Alan Ponsford. The new one is 11.2m long, nearly three metres longer.
"People have got bigger and there are rules about headroom and gangway widths, plus accessibility requirements. All of which have been welcome changes, but they mean a larger bus."
These requirements mean that although it is much bigger, it seats two fewer passengers, 62 rather than 64.
There are two staircases because the "open platform" door at the back can be open or closed, says Mr Ponsford, depending on whether there is a conductor working to collect fares and scan Oyster cards - ticket swipe cards.
The designers thought that if there was only one staircase at the back, passengers would have to walk the length of the bus before ascending.
Mr Ponsford's company Capoco Design has been responsible for designing more than half of the UK's buses in recent years. It was a joint winner of the competition to design a new Routemaster, although it was not involved in the final blueprint.
Although the old Routemaster was unique and much loved, Mr Ponsford says the design had to change.
"It was a very elegant, innovative design but this is a worthy successor because it's addressing what is new. It shouldn't be stultified by going back to what it was. You couldn't get a wheelchair on there and that was unacceptable."
Great designs - whether of products or buildings - are always related to place and space, says design critic Stephen Bayley.
"The old Routemaster is an obvious example. Because it was so evidently designed for London, it became a perfect symbol of the city. The same goes for Big Ben."
It will never have a successor, but the "new" Routemaster deserves to be a success, he says.
"It proves the old rule that if you want things to stay the same, they have to change. And it was designed for London, unlike the hated and insulting bendy-bus, which was designed for Berlin."