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.