A car crash and heavy rain haven't been enough to halt the progress of Bay of Plenty ultra-marathoner Jamie Milne as he continues his 922km run around Tasmania.

The athlete is halfway through a solo run, which he's hoping will take just two weeks. During that time he has had to battle inclement weather and wave goodbye to some of his support crew, as well as tackling the aftermath of a car crash.

Jamie Milne with one of his support crew during his run. Photo: Supplied.

But the Kiwi battler, who now calls Australia home, says he is on track to finish the treacherous journey on time.

The journey will need to be completed in the allotted two weeks because the trainer needs to go back to his job running a gym in Warana. In all, it means Jamie has to run the equivalent of two marathons a day.

Jamie told SunLive that to cover the distance he needs, which will raise funds for Hobart's Ronald McDonald House, Jamie gets up at 4am and runs for 12 hours.

With such a vast distance to cover, it hasn't all been plain sailing, and on top of battling through heavy rain, he's also had to help out at the scene of a car crash.

'It happened like 30 seconds before I got there,” explains Jamie.

'Thankfully no one was seriously hurt, but it makes you think. Life is too short and you need to get out there and do things with your life.”

He's also had to deal with his first support crew returning home, which meant for around 10km of his run he had no food or water. However, his second support crew are now there and keeping him motivated.

He's also had some fun along the way, and an impromptu twerking session when he reached Bee Hive Canal received more than 1000 likes on his Facebook page.

Jamie says he is determined to complete the journey because it's a worthwhile cause – something he knows all about. Since 2009, he has run close to 2000km and raised $55,000 for the Many Miles For Mary initiative.

The initiative was named after the Ngati Pikiao descendant's grandmother, Nanny Mary, who raised him and played a pivotal role in his life.

Jamie describes her as a 'relentlessly warm and loving lady”, but Mary's health tragically declined over 10 years prior to her death with the onset of Alzheimers.

Understanding the tragedy of the debilitating disease first-hand, and unable to farewell Mary at her tangi, Jamie made a promise to always remember his nanny in his own special way.

Many Miles for Mary, is 'a dream, a grieving process and my way of giving back. Each year I commit to great feats while raising money for charity,” Jamie says.

A man of his word, Jamie has run the length of New Zealand twice, England to Scotland and Cairns to Townsville and Port Douglas.

To donate to Jamie's cause, click here.