The 2-year-old qualified disability assist dog - wearing an identification uniform - would be attached at her waist for the race. A support team would accompany Simpson, who would be using walking poles.
Simpson said she thought a major concern for Auckland Marathon organisers had been: "What happens if I dropped the lead and he [Finn] ran out into traffic because it's on the motorway?
"But I said, look, he's going to be clipped to me. And there are also going to be a number of support workers with me. If there's any problem, there are enough people to be able to deal with him [and] help me."
Two lanes of the Auckland Harbour Bridge will be closed from 4-11am for the marathon - one for participants and the other a marshalled safety lane. The 12km Traverse starts at Smales Farm, Northcote, at 8.50am and finishes at Victoria Park.
Simpson, who would start the event at the back of the pack - "so we don't get in anybody's way" - was looking forward to the "gorgeous views" crossing the Harbour Bridge.
She was training daily with Finn from her Papakura home and they recently completed a 10.4km walk.
The 12km Traverse was a big step forward for Simpson, who said she walked with a frame and then crutches after being struck by a car four years ago.
Simpson was delighted the Marathon organisers were considering allowing the dogs.
"People with disabilities have enough limitations as it is," she said.
Williams said Finn was the only disability assist dog entered in this year's Auckland Marathon so far, but it was possible others could be allowed.
All considerations were subject to thorough health and safety checks and approvals from outside agencies, with the safety of all competitors in mind.
Finn began training when he was filmed in popular TV show Purina Pound Pups to Dog Stars, in which animal behaviour expert Mark Vette helped prepare rescue dogs for new homes.
He was one of a litter of 13. Seven were drowned in a river before someone stepped in and saved the remaining six.
Finn has been with Simpson since he was 6 months old. He goes with her to medical appointments, in supermarkets and on trains and has been beside her on flights to Wellington. Simpson plans to take him with her on a holiday to Perth next year.
Finn was also making regular visits to patients at a brain injury rehabilitation therapy unit at Middlemore Hospital and being used in a programme with at-risk youths.
• Auckland Marathon: aucklandmarathon.co.nz
