Mercedes has integrated a new rear light assembly on its W09 following a demand by the FIA to trial the system during this week's in-season test at Barcelona.
The system features a normal main rear light but red LED strips have been added to the W09's rear wing end-plates, an assembly similar to what has been used for several years in the World Endurance Championship.
The concept aims to improve the visibility of the lights for a driver following a car in rainy and heavy spray conditions.
The purpose of today's test was obviously to validate the functionality of the system rather than its efficiency given the sunny Spanish weather.
If the FIA believes the system represents a safety improvement for F1 it can simply include the change in the 2019 technical regulations without putting it through a vote to the teams.