To make traffic added by other mods use the special rules from RTD, you will need to rename some files inside the traffic packs - not the RTD mod.

Remember that you will need to rename the files after each update of a mod they come with.

Open the .scs file of a traffic mod from your Documents\American Simulator\mod folder or the Steam Workshop file C:\Program Files (x86)\Steam\steamapps\workshop\content\270880\[id of the mod]

An .scs file is a renamed .zip file so you can use Winzip, 7-Zip, or another archiver for this. In the case of a Steam Workshop mod the mod will either be loose files in folders, or it will be inside of a .zip archive.

Inside the archive or Workshop folder go to \def\vehicle\ and there rename the .sii file(s).

After renaming re-pack the archive if needed and make sure it's still got the .scs extension.

Motorcycles are any kind of two-wheeled traffic. An example is Jazzycat's motorcyle traffic.

In the case of Jazzycat's motor traffic, open motorcycle_traffic_pack_by_Jazzycat_version_ats.scs and go to the \def\vehicle\ folder, then rename the files to this:
traffic_storage_moto.jazzycat_moto.sii

Sports cars are vehicles like Lamborghinis and Ferraris, racing cars. These will want to drive at or above the speed limit in nearly all cases.

An example of a mod like this is TrafficManiac's Sports Cars: sport_cars_traffic_pack_by_TrafficManiac_version_ats_base.scs

Make sure the entries under \def\vehicle have the name traffic_storage_sport such as this: traffic_storage_sport.sport_tm.sii

Classic cars are old timers. They will drive below the speed limit a lot of times and less aggressively.
The obvious example is Jazzycat's classic AI traffic pack: classic_ai_traffic_pack_by_Jazzycat_version.scs

Make sure the entries under \def\vehicle have the name traffic_storage_classic such as this: traffic_storage_classic.jazzycat.sii