Roberts' death, as well as the deaths of Eddie Sachs and Dave MacDonald at the Indianapolis 500, six days after Roberts' crash, led to an increase in research on fire-retardant uniforms. It also led to the development of the Firestone RaceSafe fuel cell. Modern race cars use a foam-filled fuel cell to prevent fuel spillage of the magnitude of Roberts car. Also, fully fire-retardant coveralls would be phased in, leading to mandatory Nomex racing suits. Roberts had lost his close friend, Joe Weatherly, in January 1964 at the Motor Trend 500, at Riverside, California.