NASCAR has informed crew chiefs across its three national racing series of a number of amendments to the rules and regulations governing the new-look qualifying format in Sprint Cup, Nationwide and Truck Series events.

The move comes after growing concerns over safety among teams and drivers surrounding the new group-based 'elimination' way of deciding the starting grid for each week's race, which took over from the former single car, single lap time trial system used up to the Daytona 500.

However, at Phoenix and Las Vegas it was clear that drivers were running 'cooling off' laps between qualifying runs. That meant that at the same time there were some cars running at full speeds of up to 200mph while others were doing less than half that while trying to get cool air into the engine. The result was a disparity between running speeds that could potentially be disastrous.

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"The race track is meant to be raced on, not to go out and cool your race car off and get in somebody else's way. To me that's not cool," said Ryan Newman.

"That's the most dangerous thing I've ever done in a race car," said Brian Vickers after a near-miss with Reed Sorenson during qualifying at Las Vegas last Friday. "He went by me at 170 mph faster than I was going. Had he slipped or hit me, I'd be done. It would be so bad, [but] we've got to do it - it's the only way to keep the engine cool.

"We don't have impact data on 170-180mph differential impacts," Vickers added. "If I hit someone with those speed discrepancies that's going to be really bad for everyone. Unquestionably it's more exciting for the fans. It's fun, interesting, but there are some things that have to take place."

NASCAR has now responded to these concerns by banning cool down laps during qualifying, and instead allowing teams to connect cooling units to the car on pit road.

Teams are still banned from opening up the hood of the cars, however, as this would potentially enable them to make undetectable set-up changes to the car during the qualifying sessions which is not allowed. The cooling unit will have to be connected through either the left side or right side hood- or cowl-flap.

Two crew members will now be allowed over the wall to support the car and driver compared with just one previously, but plugging in the generator will not be allowed.

"The qualifying is new to all of us and as we have said over the past several weeks, we are looking at it from all aspects," said Robin Pemberton, vice president of competition and racing development. "Following discussions, both internally and with others in the garage area, we moved quickly to make a few revisions.

"We believe this will only enhance and improve what has demonstrated to be an exciting form of qualifying for our fans, competitors and others involved with the sport," he added. "Moving forward we will continue to look at it and address anything else that we may need to as the season unfolds."

The changes take immediate effect with this weekend's events at Bristol Motor Speedway, which at just 0.533 miles in length is the shortest oval on the series' schedule.