London is getting serious about transitioning to a more sustainable, environmentally friendly system of public transport, with Mayor Boris Johnson announcing that the world's first zero-emission electric double-decker bus will be ferrying passengers around the city by October this year.

Announced at the first annual Clean Bus Summit last month in London's City Hall, the move will see emissions from the city's bus fleet - touted as being one of the cleanest in the world - reduced even further. Following suit, a total of 24 world cities committed to rolling out over 40,000 ultra-low emission buses by 2020 at the global summit. A number of vehicle manufacturing giants, including Volvo and Wright Bus, were also in attendance.

According to Chris Wood a Gizmag, London has been firmly on the path to greener public bus systems since 2008, when it committed to putting its first hybrid buses on the city streets. Since then, more than 1,300 hybrid buses have been in operation around the city, with another 1,400 retrofitted to reduce emissions by 88 percent, Michael Rundle reports at Wired UK.

Now, under the direction of Mayor Johnson, the city will be focussing on getting a fleet of purely electric buses out there, starting with the iconic red double-decker. It will take on Route 16, which runs between Cricklewood in the northwest of the city and Victoria Station.

"I could not be more pleased that London will play host to these exciting pure electric double-deck buses, and I'm sure the lucky users of route 16 will embrace it with gusto," the Mayor said in a statement. "London is a world leader in clean buses but we can't do it alone, and events like this Clean Bus Summit are key to making further progress."

At the summit, the Mayor has committed to making sure that by 2020, all 300 single-deck buses in central London will be zero emission at tailpipe, and all 3,300 double-decker buses in central London will be at least electric hybrid, if not purely electric. 

While the announcement is definitely exciting, it's not been an easy task to get things to this stage. The Mayor said many believed that a purely electric double-decker bus was impossible because of the giant battery packs needed to power it, but vehicle manufactures, BYD, have managed to shrink the technology down so the bus can travel for more than 250 km (155 miles) in heavy city traffic on a single charge.  

Hopefully the city will stay true to its word in getting all these electric and hybrid buses out there. As Wired reports, "London remains critically far from meeting crucial air quality standards - with local joggers warned to avoid parts of the city during high emissions periods."