Many German motorways use that system and have dynamic speed limits based on the current traffic situation. The downside is that most people think »Why the hell

Many German motorways use that system and have dynamic speed limits based on the current traffic situation. The downside is that most people think »Why the hell should I drive 100 now when I can still drive 120?«, so depending on the mindset of the drivers this may or may not work. I rarely see those speed limits followed or enforced.