After the incident at the German Grand Prix where a cameraman was hit with a loose wheel and sent to the hospital, the FIA first banned all non-needed crew from the pitlane during races and qualifying, and now it is going one step further by mandating all teams use a two-stage wheel retention system. The current systems are still legal for next week's Italian Grand Prix, but they must be replaced by the Singapore Grand Prix on September 22.

The rules already forced all teams to use wheel retention systems that prevented wheels from detaching form the car during crashes and harming people nearby, but the teams were able to design their own systems. Under the rule change all teams must use a system where the wheel will stay on the car even if it has not been attached correctly like a nut being cross-threaded as happened in Germany. 

The FIA calls the new rule the dual retention system because the previous system that kept the wheel on the car during crashes is still mandated. 

The rule change came during the F1 August break, and McLarenMcLarenUnited Kingdom, 1963 > present92 models
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already tested its system at the Belgian Grand Prix. 

"We tried it on the car on Friday [in Belgium] and we will probably put it on the car for Friday at Monza as well. 

"It is a little bit different and, when you are operating with pitstops around two seconds in length, the most marginal things can make a big difference. Just a tiny change to the design can really disturb the mechanics and their whole routine," said McLaren sporting director Sam Michael.

Source: Autosport