Ah, you mean the traffic that's present in the original first release of New York conversion, made by Richard P. and Yallis.
If you want to have it in the SuperSecret's improved version, you need some to delete all the files in the original New York .ar file except all the ones of that traffic. Practically you'll get a traffic mod only for any New York release. Or, since the traffic mod included in
this release is the same but made to work only for the default game cities, it's enough take the file as_manhattan.aimap from the original New York .ar file and put it in the .ar file of the traffic mod of that release; the folder where it has to go has to be the same, of course, called City.