The innovation upgrades static bus-side ads to moving images, which can be updated at different times of the day.
Twenty-five buses have each been fitted with one screen on the pavement side, meaning that the ads will be seen more by pedestrians than drivers. Transport for London and three bus companies operating the buses involved in the campaign have approved the screens.
Jon Lewen, digital account director for Viacom, said he believes the screens are a world first, although Viacom has already used lower-resolution LED screens on buses in a campaign for Nike in summer 2002.
Stuart Parish, Lastminute.com's media planning and purchasing manager, said: "The sites will offer us a standout and impact that will be hard to ignore and I'm confident they will be a huge success for us. While we can't give any more detail at the moment, it goes without saying that when Lastminute.com paints London buses pink with its cheeky advertising messages, it'll be hard to miss."
Viacom has been testing the application at the same time as installing and testing digital escalator panels using similar technology at Tottenham Court Road Tube station. The Tube digital panels have attracted advertisers such as Direct Line.
The bus screens take up half of the normal rectangular "superside" ad space and they measure roughly 3m by 0.8m.
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