The catalyst for developing racing suits that could effectively resist fire came in the late 1950s and 1960s, when several fiery crashes occurred in the motorsport world. In 1959, Jerry Unser died from burns suffered in a crash practicing for the Indianapolis 500. In 1963, NHRA Top Fuel driver and Division 7 Tech Director Chuck Branham died after suffering burns in a crash. During NASCAR's 1964 World 600 (today's Coca-Cola 600), Fireball Roberts was involved in a crash on lap seven while avoiding two other cars, passing away five weeks later. Roberts had asthmatic reactions to the clothing treatment used by NASCAR, and had received a waver against using it. One week later during the 1964 Indianapolis 500, drivers Dave MacDonald and Eddie Sachs were killed in a seven-car crash on the second lap of the race.