I'm not so sold on the Autobahn.
Traffic densities are generally quite high. German drivers are incredibly aggressive, and the expectation is that there is a righ to speed, though to their credit, the "fast lane" is a passing lane, and there is no tendency to lane hogging that's so common in the US (don't get me started on midwest drivers) is gone. What you've got to worry about is the speed differentials. Trucks are restricted to 110 km/h, meaning they're doing about 65 MPH. I found 140 km/h was a comfortable speed (85 MPH -- about what I drive in the US, given open highway), which was about normal, though the fast lane traffic was far above this, with 200 kph (120 MPH) not uncommon.
Problem is when there's a traffic slowdown, and these come from several causes. Speed is restricted in urban areas. Speed limits are dynamically set to road conditions (not altogether a bad thing), indicated by electronic signs on the highway, but this means you can't count on knowing the speed limit for a given stretch of road. Worst is when there's some sort of tie-up. Traffic goes from current speed (65, 85, 120 mph) to a crawl, in seconds. This is where horrific accidents occur, Germany's notorious for families being wiped out in an instant on the highways. Stories of trucks jacknifed across highways and cars running underneath them....
It's interesting, but a bit high-tension for my tastes. Nevada state route 375 is an entirely different issue.