Lewis Hamilton has been running in Barcelona Formula 1 testing today with a strip of red lights mounted in each rear wing endplate of his Mercedes W09.
The test is being conducted at the request of the FIA as a possible solution for improving visibility in heavy spray conditions, although sunny conditions in Spain meant that the test could only really prove the functionality of the device.
Although the deadline for the 2019 F1 technical regulations has in theory passed, changes can be made with a unanimous vote, and in addition any safety improvements can simply be mandated by the FIA - as was the case with the Halo, which wasn't officially confirmed until late July last year.
Rear endplate lights are not a new invention, having already been seen on prototypes in the World Endurance Championship for several years, but this is believed to be the first practical single-seater version.
Design consultant Chris Beatty, who had some input into the 2018 IndyCar concept, noted today on Twitter that he has previously suggested endplate lights that show green, red, yellow and blue flags to following drivers.