Sprint Cup driver AJ Allmendinger will not appeal the positive result in a random drugs test that has seen him suspended indefinitely from all NASCAR competition, and has said that he will immediately start the mandatory 'road to recovery' treatment and rehabiliation program he needs to successfully undertake before he can be reinstated.

"He's officially on the 'road to recovery,'" NASCAR spokesman David Higdon said on Wednesday. "In fact he just signed this afternoon [the] letter that provides him the first steps," he said.

By signing the letter, Allmendinger accepts the drug test findings and waives his right to an appeal under NASCAR's substance abuse rules.

"We're very pleased that AJ Allmendinger has chosen to participate in the NASCAR Road to Recovery program," NASCAR's official statement on the matter said. "It's designed, as proven, to provide a roadmap leading to a return to competition, and we wish him the best of luck. As we have with other competitors, we look forward to the day when the program administrator recommends him for reinstatement."

Allmendinger's business representative explained why the driver had decided to act quickly to sign up for the program, even while some aspects of the drugs findings remain unclear.

"We made the decision this morning to do that, and exhaust every resource that we can, including those that have been given to us by NASCAR, so that we can make that process as quick as possible," said Tara Ragan, the vice president of Walldinger Racing Inc. "We didn't want to wait. We've already lost a lot of very valuable time. We didn't want to sit here and wait."

There's still some confusion over whether the precise nature of the substance that caused Allmendinger's positive result, with different media sources carrying different stories. In some, Ragan appears to be waiting for confirmation from NASCAR as to the substance involved, while in others she is reported as confirming that it was an amphetamine.

"It was not cocaine, not ecstasy, not marijuana, not alcohol. Those are not stimulants. Not methamphetamine. The test does show that it wasn't any of those," Ragan told SPEED TV channel's NASCAR magazine show. "There are things we know that it's not. We haven't been informed yet of what it is."

NASCAR's David Higdon insisted that individuals found to have violated NASCAR's banned-substance list are informed of "the exact substance that he or she has tested positive for," in the letter that they receive formally notifying them of the positive finding.

Ragan subsequently clarified why her answers varied between interviews: "We weren't being evasive ... In my head, no, we didn't know what the drug was. Amphetamines was too general for us when trying to figure out what it is."

Allmendinger's team still insist that the driver did not knowingly or intentionally take any banned substance, and that they are still trying to work out what could have caused the positive result. Fan speculation has centred on diet and nutritional supplements or sports energy drinks being to blame, but there is no evidence supporting this so far. Allmendinger's team have previously spoken of getting all the driver's supplements tested by an independent laboratory to try and get to the bottom of the source of the problem.

"We look to rule out the possibility of a supplement being involved," said Dr David Black, who will co-ordinate Allmendinger's 'road to recovery' program. "I'm not aware of any commercial products that would have influenced the test outcome."

Since each 'road to recovery' is a bespoke creation for each individual based on their nature, the substances involved, and their response to treatment, there is no definite time span for the program which is why a driver is listed as being on 'indefinite' suspension in the meantime. The process starts with an evaluation by a substance abuse counselor to set up the program for Allmendinger's treatment, which typically also includes a series of further drugs tests.

However, it is not meant to be a quick or easy process, as medical officers have to be convinced that any underlying problems have been addressed and that the individual is not at risk of relapsing. Allmendinger is not expected to be back this season, and given the public relations issues surrounding the test results it's possible that even once he does complete the 'road to recovery' process he might find it difficult to find another top team ride in NASCAR in the near future.

The only other Sprint Cup driver to test positive in a random drugs test was Jeremy Mayfield in 2009. He never signed the letter agreeing to participate in the 'road to recovery' process and instead embarked on a long and increasingly bitter legal dispute with NASCAR over the test results, to no avail. He remains on indefinite suspension, and is currently on police charges for other unrelated matters stemming from a police raid on his residence at the end of 2011.

In the meantime, Sam Hornish Jr. will continue to drive the #22 Shell/Pennzoil Penske Racing Sprint Cup car at the next two races at Indianapolis and Pocono, after which the team will make a longer term decision. Allmendinger was signed to the team for a one-year deal at the start of 2012, to replace Kurt Busch who left at the end of the previous season.

"I think the situation is going to continue to be fluid," said Penske Racing president Tim Cindric. "It's way too early for us to speculate on what A.J.'s future holds with us."

Cindric told SPEED Wednesday that, "I think Roger [Penske] has said all along that his biggest concern is really for more about the individual, than anything else. We as an organisation are certainly very sympathetic to the situation that AJ's going through."

"You never give up hope in terms of AJ's situation," stressed Cindric. "I think the best thing that he can do is to continue to do what he is doing, and work with NASCAR to understand what process and what steps he needs to take to be reinstated in the Cup garage. I think that's where his priority needs to be right now."

As for Hornish's position: "Sam has certainly done a great job under difficult circumstances because he has to adapt to new people and new things. I think that he'll continue to get more comfortable as we go through a couple of more races.