Computer-generated moving adverts will soon be appearing on London buses.
The displays are similar to the screen in Piccadilly Circus
Viacom Outdoor is to install the screens on the side of 25 buses operating in central London and will be in use from October.
The displays, half the size of full-length bus posters, will be on the pedestrian side to allay fears they may cause accidents by distracting drivers.
This year, the company installed 66 similar panels along the escalators at Tottenham Court Road Tube station.
Viacom Outdoor said it had been working on the digital bus sides, as they are known, for a couple of years.
The company also said they were similar to the advertising boards at Piccadilly Circus.
John Lewin, an account director at Viacom Outdoor, said he could not name the first company to use the service but thought it would attract a number of advertisers.
"We have been exploring this for a couple of years and we are very excited by this," he told BBC News.
"This gives us more scope in advertising allowing advertisers to change quickly, keeping the message relevant.
"We think it will be a big success. It is a good way to hit a large number of Londoners in a very interesting way."
He added they had to address the concerns of Transport for London and the bus companies about the ads distracting drivers.
Mr Lewis said: "Last year we ran a campaign for Nike using a much simpler LED screen on the side of the bus and we had no issues with that.
"This is a trial. We have to make sure everyone is happy with it before we take it any further."