Map app for avoiding gravel roads I use Google for mapping out long distance tours in areas I don't know. Often it takes me on gravel roads. I can't tell from the app that is not really road bike friendly till I get there. This can really mess up my plans (since I may I have to back track and go around adding hours to the day and getting to my camping destination.

That said - any favorite apps for bike travel - camping? Maps?  (I do have warm showers!  Love it for emergencies!)
There is no tool that I know of that solves your problem for you. 

The way I solve the problem of finding out what a road is like, is to 


use Google maps to find a route. 
then use Street View to check the roads at important points. Of course, if the road is gravel, Street View is probably not available. 
if the route is not what I want, drag the route line to another road, and check that.


In addition (I didn't know about these and haven't tried them) there's Gravel map and similar sites that perhaps could be used to see where the gravel is, so you can avoid it.