Before SCS' Rhine Region Revamp, Old Duisburg was using old assets. There was barely any city to explore. One lane roads that went in a rectangle. TMP had to make the city NCZ. Even then, it was still a traffic nightmare. Then, TMP added a custom Duisburg. Everything flowed except for the exit of the repair shop. The base game was designed for Single Player. I have personally suggested a secondary exit out of Current Duisburg. I was told, just use the other highway ramp to go East and just loop around.
I have to avoid Duisburg by taking the interchange to the west of the rest area's. Once i hit the problem, i'll lag as the game tries to loading 100+ players. And if i F7 into Duisburg, i'm kicked for "unreliable connection" because i'm loading 200 players and the city at the same time.
As for Speed Limits, 60 is fair within the city (even though some speed limits are 30). And 110 outside. The problem is, their speed limit script detects where the city zone is and lets speed increase as you're leave (70, 80, 90, You have left the city). Instead of just bounding the speed limiter to the road limit being driven on.