What is the safest interpretation of the red areas around the truck in this diagram?

Their exact extent varies with vehicle, mirrors and conditions. Seeing the truck does not prove its driver sees you. Keep clear, particularly of its left-side blind area.

ʻOku kehekehe ʻa honau lahi moʻoni ʻo fakatatau ki he meʻalele, ngaahi sioʻata mo e tuʻunga. Ko hoʻo sio ki he loli ʻoku ʻikai fakamoʻoniʻi ai ʻoku sio ʻa hono fakaʻuli kiate koe. Nofo mamaʻo, tautefito mei he feituʻu puli ʻi hono tafaʻaki toʻohema.