Good mod but the tutorials are all over the place, Just download his other csp-traffic-tools from here (all the other ones didn't work for me)
https://www.p atreon.com/posts/27-more-cars-for-77042592
and put the csp-traffic-tools folder in this path:
"\SteamLibrary\steamapps\common\assettocorsa\extension\lua\tools"
at least that's what worked for me (also don't forget to delete the old folder which was in "SteamLibrary\steamapps\common\assettocorsa\extension\lua")