London's iconic double-decker buses have gotten an update that looks uncannily like the past.

Seven buses with an open hop-on hop-off platform at the rear hit downtown streets on 20 February, running on route 38, between Victoria Station and Hackney, an east London neighbourhood.

Between the 1950s and 2000s, royal red double deckers sported distinctive open platforms in the rear. But in 2005, authorities took that Routemaster model out of service, replacing it with versions that only have an entrance at the front.

The city also added so-called “bendy", or articulated, buses, because they could carry more passengers, thanks to hinged midsections. But locals loathed the replacement vehicles. A common complaint was that the extended length of the buses snarled traffic on many narrow, twisting streets. So the city pulled that design off the streets in 2011, leaving regular double-decker buses in service and shipping the bendys off to other cities in the United Kingdom that have more spacious streets. Officials then ran a design competition to see if a better bus could be invented. The design that won, by Thomas Heatherwick and Wrightbus, restored the open rear platform.

The revived Routemaster design adds a second staircase to speed up passenger movement. It also claims to get a low 12 miles to gallon thanks to energy efficient engines and interior-heating systems. That efficiency means it produces 40% fewer emissions than the current double deckers, which run on diesel.

The success of this design depends on the outcome of this spring's mayoral election. If candidate Ken Livingstone defeats current mayor Boris Johnson, he may kill the new Routemasters, which are Johnson's pet project and cost about £1.3 million each, significantly higher than more prosaic models. A Johnson victory, on the other hand, may mean that hundreds of the buses are put into services within the next few years.

In the meantime, original 1950s buses with the open platform in the rear are still in service on parts of route 9, running between Trafalgar Square and Kensington, and route 15, running between Trafalgar Square and Tower Hill. Check the Transport for London website for route maps and schedules that say "heritage".