I just disabled the 'Deutsche Autobahn' MODyou can manually edit the ini file that deals with AI speed, for example for the two_way layout :
C:\Program Files (x86)\Steam\steamapps\common\assettocorsa\content\tracks\la_canyons\traffic_two_way\data
file called ai_hints.ini
...[MAXSPEED_15]START=0.5976END=0.7698VALUE=115[MAXSPEED_16]START=0.7698END=0.7705VALUE=50[MAXSPEED_17]START=0.7705END=0.9146VALUE=115...
here you have different sections of the track, and value="115" for example, i believe this is in km/h
so reduce all the values to 80 for example. Try not to raise values, or they will most likely go too fast in tight corners or something
and don't forget to backup the file
jokes aside: very helpful info you shared with us. Thanks!