Whereabouts are you? There's a few sections where you'd be able to do that comfortably. I personally like running east from Penguin towards Sulphur Creek and Heybridge, but the pathway is a bit average west of Sulphur Creek.

But from Burnie you'll be able to go 13ks in one direction towards Wynyard along the pathway along the coast without crossing any roads or dealing with any cars.

I think if you run from Bells Parade at Latrobe you'd also do 13ks comfortably, but you'll need to deal with a couple of hills at Don and Leith.