In October, 1969, "Crash Survival:Help from the Tracks" in Nelson, Automotive Industries, Vol. 141, No. 7, noted that for the 1965 Indianapolis 500 race
" . . . all competing cars were equipped with fuel cells. These bladders are made of tough, rubberized fabric stuffed with foam. * * * Impact resistance fuel cells remained intact and eliminated the threat of fire. * * * NASCAR has required the fuel cells since 1966, USAC made them mandatory in 1965."
The 18th Stapp Car Conference concluded that "increasing the thickness of the tank provides a direct approach to improved fuel integrity. Research has shown that plastic tanks of high-density poly-ethylene have about the same dynamic rupture resistance as conventionally constructed metal fuel tanks."