Complete the following sentence: Roberts' death, as well as the deaths of Eddie Sachs and Dave MacDonald at the
Indianapolis 500,<unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> It also led to the development of the Firestone RaceSafe fuel cell.<unk> It also led to the development of the Firestone RaceSafe fuel cell. ️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️ ️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️ Roberts had lost his close friend, Joe Weatherly, in January 1964 at the Motor Trend 500, at Riverside, California.<unk> Roberts had lost his close friend, Joe Weatherly, in January 1964 at the Motor Trend 500, at Riverside, California.