 Complete the following phrase:  Following a series of serious incidents in open-wheel racing  including the fatal accidents of Henry Surtees and Justin Wilson  in which drivers were struck in the head by tyres or debris, the FIA announced plans to introduce additional mandatory cockpit protection with 2018 given as the first year for its introduction. Several solutions were tested, with the final design subject to feedback from teams and drivers. Each design was created to deflect debris away from a drivers head without compromising their visibility or the ability of safety marshals to access the cockpit and extract a driver and their seat in the event of a serious accident or medical emergency, with a series of serious accidents  such as the fatal accidents of Jules Bianchi and Dan Wheldon  recreated to simulate the ability of devices to withstand a serious impact. The FIA ultimately settled on the halo, a wishbone-shaped frame mounted above and around the drivers head and anchored to the monocoque forward of the cockpit. Seventeen accidents were examined as case studies, with the FIA concluding that the halo would have prevented injuries in fifteen of them. In the other two instances  most notably 