Penske Racing driver Brad Keselowski was taken to hospital on Wednesday afternoon after a major accident during a test session at Road Atlanta, as teams prepare for the upcoming road race at Watkins Glen.

While Keselowski was able to exit the wrecked car on this own, he was clearly very shaken but awake and alert. His car - the famed #2 "Blue Deuce" - was a complete write-off after apparent brake failure resulted in the car hitting the wall head-on at the turn 1 corner at a speed of over 100mph, at a point lacking a modern impact-absorbing SAFER barrier.

The organisers quickly had Keselowski airlifted to the nearby Atlanta Medical Center to be properly checked over as a precaution, but Keselowski himself was quick to take to Twitter to update fans who had heard the news and were anxious about his condition.

"In a serious accident today while testing Road Atlanta. Hit wall head on in a 155mph corner after brakes failed. Airlifted to hospital," his first tweet read. "Looks like I'll be ok to race this weekend [at Pocono]. Blue deuce, not so much. I'll keep u posted."

Keselowski also subsequently posted pictures of some scrapes and lacerations, and a very badly swollen left ankle, but added that the X-rays of his feet and ankles looked good and that he didn't have to stay in hospital overnight.

While still being evaluated and treated at the medical center, Keselowski was already getting back to work trying to analyse and understand exactly what had happened. "Looking at data with engineers in hospital bed. Was going 155, car slowed to approx 100 before hitting a non safer barrier wall head on," he tweeted.

Jimmie Johnson - who had also been participating in the test - later posted a picture of the wrecked #2 to his own Twitter feed. He also posted pictures of the damage done to the wall in turn 1, and the rubber trail laid down on the way to the point of impact.

"Glad you're alright man, you had us all worried," he tweeted to Keselowski, whom he called "one tough dude, I can say that much". Johnson admitted that "He had us all very concerned... The chopper coming to get him freaked us out too."

"When it takes a front end loader to bring your car back...that's a hit my friend," tweeted TNT NASCAR pit reporter Matt Yocum. "Glad you're ok."

The drivers are not allowed to test at the Cup venue itself, so that no one gains unfair advantage over anyone else before the race. However, with this resulting in drivers having to resort to testing on non-Cup second-tier circuits without the more modern and expensive safety equipment in place, Keselowski's accident highlights the question of whether this is a safe practice for the series and teams going forward.

As well as testing at Road Atlanta in preparation to competing in the Cup race at Watkins Glen, Jimmie Johnson has also just been "signed up" by his Hendrick Motorsports team mate Dale Earnhardt Jr. as the driver of the JR Motorsports #7 Nationwide Series car for that weekend, as Johnson seeks additional experience at the historic road course venue ahead of the Cup race at the circuit.

It will be Johnson's first Nationwide Series start in three years. Previous occupants of the #7 Chevrolet in Nationwide this season have included Earnhardt Jr. himself, Danica Patrick, Josh Wise, Ron Fellows and Kasey Kahne.

Keselowski by contrast has competed in all but one of the 21 Nationwide races this season, and last weekend won the final series event at Lucas Oil Raceway outside Indianapolis to claim his second victory of the year. He also has one Cup victory to his credit this year - at Kansas in June - but is currently in 21st place in the points standings and out of contention to claim one of the wildcard spots for the Chase based on race wins.