Not being a GPS user (that's cheating), most paper road maps have notes on them noting steep and narrow roads. I will use Google maps once in a while. Then there are the signs on the narrow road "suggesting" that trailers aren't recommended or even prohibited. Blew by one of those in southern Utah and they weren't kidding, very steep, almost lost the brakes.
On Route 66 east of Oatman, the road is narrow and curvey, semi's aren't supposed to be on it, but met one on one of those curves. Or for fun you can go thru Jerome Arizona squeeze around corners in town, then head south on 89 and hit more tight curves and steepness. Then there's the highway that heads south from I-70 near Green River Utah down to Monument Valley where the signs say no trailers. They are right on this one cause as it descends off of a mesa, its, dirt, much of it one lane and really steep. Fun to drive solo though.
My problem is I see those "don't do it" signs to be a challenge to my manhood and driving prowess. Wife usually prevails though. Never had a ticket or accident so I am very careful at all times.