The raceway calls itself the "Fastest Dirt Track in the East." It consists of a spacious 5/8-mile high-banked dirt oval, where average speeds reach well over 100 miles per hour, according to the track's website.
Leffler, 37, of Huntersville, North Carolina, was rushed to the Crozier Hospital in Chester, Pennsylvania, where he was pronounced dead at 9:02 p.m ET, the New Jersey State Police said.
Sprint car races can be more dangerous for drivers and spectators because the safety measures taken by series aren't at the same level. Many facilities lack the SAFER barriers that are standard in NASCAR and IndyCar, and the cars aren't always adequately protected.