NASCAR banned drivers from racing back to the yellow flag under caution, changing a rule strongly criticized by drivers and team owners.
The new rule, which takes effect for this weekend's races, forbids passing once the caution flag is displayed. NASCAR President Mike Helton said Thursday the change was needed "to further ensure the safety of the competitors."
Drivers had been allowed to continue racing at full speed under caution until they got back to the flagstand at the finish line.
At that point, they had to slow and line up behind the pace car.
Despite the old rule, drivers had been expected to follow a gentleman's agreement and hold their positions when the caution flag came out. That agreement was often ignored.
In other NASCAR news, Busch Series driver Shane Hmiel was suspended indefinitely for violating the substance abuse policy.
"NASCAR has a zero tolerance for any type of behavior in violation of our substance abuse policy," Helton said.
Helton did not specify the substance involved, but said Hmiel could seek reinstatement after agreeing to attend counseling and undergo periodic random testing.