The huge new screens will feature new cameras able to detect drivers and car models and stream adverts targeting individuals.
The billboards were switched off last year for the hi-tech upgrade and the 790m² screen is due to be re-lit in October with test modes currently being displayed.
And when they do get turned back on, hidden cameras will log make, model and colour of passing cars.
An estimated 100 million people pass through Piccadilly Circus every year, according to Landsec which operates the screens, making it one of the world's most prime advertising spaces.
Specific adverts will then be pre-programmed to automatically trigger when certain cars pass by, according to Landsec.
The cameras can also judge gender, age and even mood of the driver and pedestrians to deliver targeted ads.
The new single screen - with 11million pixels - replaces the old six screen layout and is the largest of its kind in Europe.
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