Having rigorous enforcement of minimum radius in curves*, preserving more available cornering/braking traction and wide lanes, providing for better sightlines ahead (for faster traffic) and behind (for slower traffic contemplating pulling out to pass even slower traffic).
* - I did an internship for Mercedes in the early 90s and we had testing access to a section of ex-A8 near Stuttgart that was retired because it didn't meet the modern autobahn requirements and so had been replaced with a re-routed A8. To my American college-student mind that seemed incredibly wasteful, but it sure was convenient for our testing. I can't find it now on Google maps, but it's been 30 years so may have been demolished by now.
