British supermarket chain Tesco is installing face-scanning cameras at its 450 gas stations across the U.K. to target customers with customized ads.

Cameras at each register will scan customers' facial features to determine their gender and age range, and then a targeted ad will pop up on a nearby screen intended to spur an impulse buy. 

The system is 95% accurate in spotting men and 87% accurate in spotting women, according to an independent study on the website of French company Quividi, which developed the software. The system, which is licensed by the British firm Amscreen, has raised some privacy concerns.