Highway signage, not dashboard chrome. Barlow Condensed for numerals and labels — the condensed, uppercase language of interstate signs. Numbers are the largest thing on every screen.
Sodium amber on near-black. One accent for action and route, green for safe/legal, red-orange for hazards, cyan reserved exclusively for PI. Nothing else gets a color.
PI is the center tab, always reachable. A cyan orb at the middle of the tab bar and a toast lane during navigation, so it can speak up without stealing the road view.
Trucker assumptions. Hours-of-service clock on home, truck-legal route comparison with clearance warnings, expenses auto-captured from the fuel card, mileage reimbursement export. Tell me if any of that is wrong for your users.