FORT WORTH, Texas--Championship Auto Racing Teams announced Sunday that it was postponing the Firestone Firehawk 600 Presented by Pioneer at Texas Motor Speedway due to extensive concerns over the unprecedented physical demands being placed upon its drivers.
"We are postponing the Firestone Firehawk 600 Presented by Pioneer due to concerns over the physical demands placed on our drivers when traveling at speeds of more than 235 miles per hour on this 1.5-mile oval," 
The concerns became magnified following Saturday morning’s practice session, after which several drivers reported lightheadedness or dizziness when spending stints of 20 or more laps in the cockpit. 
With the increased speeds came an attendant increase in the amount of gravitational force, both lateral and vertical, experienced by the drivers while in the cockpit. On the 1.5-mile oval, drivers sustained loads of up to 5½ Gs for 18 of the 22 seconds it took to complete a single lap.