Unsworth said it was much needed as the "dire state" of roads was a major concern for the AA's 1.5 million members.
"We can tap into that membership to find out what our motorist members are saying, and a lot of them are talking about the quality of roads.
"It's down to not spending on the maintenance.
"We can lower the speed limits, which the government are seeming to do but that, in my view, is missing the point.
"They're dropping our speeds because it's easier than fixing the roads. You don't have to spend any money except for changing a few signs from 100 to 80 [km/h]."
Unsworth said he was stepping down to make time for his other commitments.
He has chairman roles for Sport Whanganui, Whanganui Hospice Foundation and Whanganui Boys and Girls Gym Club Trust, and his fulltime job as a partner at law firm Horsley Christie.
"It's been really quite time-consuming, but it's rewarding, valuable and enjoyable. So it balances that out," he said.
"It's been really rewarding and you feel you're making a bit of difference because there are a lot of AA members throughout New Zealand, and in particular in Whanganui."
Unsworth hoped to see the AA evolve to better reflect New Zealand society.
"We all drive," he said.
"That's why the AA is there. To look after the motorists. So it would be really good if we could get a better reflection of New Zealand society. So gender, age and ethnicity are represented on our district council. It could benefit from younger people, females."
In other areas AA was evolving, he said.
"There's a battery service on the road now, and they're also moving to get an electric vehicle road service so if your EV breaks down you can get an instant charge.
"There's even a service to pick up your e-bikes if your battery goes flat. That's quite groovy eh?"
Russell Cameron has taken over as chairman of AA's Whanganui council.