The hope is that the new displays will be both readable and environmentally friendly. Like a Kindle, they should be readable in bright sunlight and draw less power than a conventional full-colour screen. TfL says they can be charged from a solar panel too, and retrieve bus arrival information over 3G. For now, it's only available in one location, near Waterloo Bridge, although the plan is to introduce a further three in Parliament Square, Piccadilly Circus and Sloane Square next month. They're be trialled until the autumn -- a full roll-out is probably too expensive, but this should give TfL a better idea of its viability.