The light tree uses a colour-coded system to communicate directly with the driver. Red signals that the car must remain stationary while work is in progress. Green indicates that all pit stop operations are complete and the driver may leave the pit box. The system is controlled by a team crew member monitoring the stop from the garage, who triggers the green once the wheel-change sensors confirm every corner is ready. The suspended position of the lights — directly in the driver's line of sight above the cockpit — means the signal is visible even while the car is surrounded by mechanics.
Sensors fitted to the pit box detect when each wheel-change operation is complete. Only when all four sensors have confirmed safe installation does the system permit the release signal to be given. This automation both accelerates the decision and reduces the risk of the car leaving with an unfinished tyre change, a source of dangerous incidents in the era of manual lollipop release.
The traditional lollipop man held a large circular team board to serve three purposes: identifying the pit box for the incoming driver, holding the driver stationary during the stop, and signalling departure. As pit stops became faster and choreography more precise, the hand-held sign became a bottleneck and a point of human error. The automated light tree allowed teams to remove one additional manual judgement from the sequence, tightening the overall stop time by ensuring release is triggered only when the system confirms the work is done.
The reliability of automated release systems was tested at the 2008 Singapore Grand Prix, when Ferrari experienced a malfunction in their sensor-driven light system. The malfunction contributed to a pit stop incident involving Felipe Massa. As a result, Ferrari temporarily reverted to using the traditional lollipop man for subsequent races while the automated system was reviewed and reconfigured. The incident highlighted the dependency modern pit operations have on sensor accuracy and the importance of fallback procedures in the event of system failure. The light tree system nevertheless remained the standard across the rest of the field, and Ferrari returned to the automated arrangement after rectifying the fault.
In the current era, Formula One mid-race refuelling has been banned since 2010, and pit stops consist primarily of tyre changes with occasional wing adjustments or minor repairs. With stops measured in under three seconds at the competitive end, every element of the procedure — including the speed of the release signal — contributes to overall stop time. The light tree is one component of a fully choreographed operation involving up to twenty crew members, pneumatic tyre guns, lever jacks, and a tight sequence of roles that must be executed simultaneously for a competitive result.
The world record for the fastest Formula One pit stop is 1.80 seconds, set by McLaren during the 2023 Qatar Grand Prix.