Magnum-owner Unilever is launching a new campaign that will see heat sensitive digital adverts placed on the roofs of black cabs in London.

In order to activate the adverts, the taxis will use BrightMove Media’s TaxiCast digital advertising technology to detect when temperatures rise above 19°C (16°C when the sun is out). The technology is also claimed to respond to the ‘ideal humidity and brightness’ for selling ice creams.

The adverts will come in the form of roof-mounted displays that are capable of showing digital real time messages from a dual-sided LED screen.

The taxi-top adverts are being rolled out onto 25 London cabs throughout July, after Transport for London gave the campaign the go ahead.  

Piers Mummery, chief executive of BrightMove Media, said, “Magnum’s targeted campaign is a fun way to ensure when the sun comes out, so do the ice creams – perfect timing for the summer heat wave.”

The three-month trial is part of Unilever’s £2m advertising campaign to support the new Magnum Kisses ice cream range.

Elsewhere in London, a charity called Plan UK tried using facial recognition technology last summer to determine the gender of people on Oxford Street and to deliver its equal rights message.

The interactive display at a bus stop opposite Selfridges department store aimed to highlight the issue of women and girls in developing countries facing poverty and discrimination.