Why are there pit lane speed limits and how are they measured?

The unique configuration of the Monaco pit lane has proven to be a frequent source of penalties in the Formula 1 World Championship. Due to the tight and congested nature of the circuit, the standard 80kph pit lane speed limit is reduced to 60kph, a regulation strictly enforced by FIA timing loops and transponders. During the recent Monaco Grand Prix, several drivers fell foul of this rule, leading to time penalties that significantly impacted the race results. While some drivers like Lewis Hamilton and Oscar Piastri successfully served their five-second penalties during pit stops, others faced difficulties; notably, George Russell incurred a drive-through penalty after failing to correctly serve his initial five-second penalty before servicing his car.