This app was mentioned in 2 comments, with an average of 2.50 upvotes
The reviews scare me a bit for CoPilot. Seems to have lots of map accuracy issues. Have you had any problems?
Co-Pilot is the mobile version of PCMiler and they offer different versions for regular cars and for truck drivers. It can be purchased for Android or Apple devices. It also works in off-line mode so you won't abuse your data plan while on the road.
The truck version may seem expensive, but compared to the cost of the PC version it's pretty cheap.
http://blog.copilotgps.com/na/2017/02/24/how-to-avoid-bridge-strikes/
They have a specific version for RV drivers here:
https://play.google.com/store/apps/details?id=com.alk.copilot.namarket.premium.rv
https://itunes.apple.com/us/app/copilot-rv-usa/id1080395403?mt=8