Forget that mod, pretty sure it causes all manner of problems including crashes for some.
I think I tested it years back & it never worked for me either. I'm honestly not sure why it would?
'vehicleaihandlinginfo.meta' has nothing to do with spawning afaik, but perhaps it can be used to break the game & stop spawning occurring etc, at least back in 2015 anyway.
The best way to remove traffic is to edit 'popgroups.ymt' & remove all the vehicles.
That way you will also get a bonus performance/framerate increase (you don't get the performance increase if you use a trainer to remove traffic, for example).
Here is an already decrypted 'popgroups.ymt' with all the vehicles removed, just drag & drop it into the game here (after making a backup of 'update.rpf' obvs):
Note: 'vehiclemodelsets.meta' may still spawn the occasional vehicle around Los Santos (modded/upgraded cars, planes at Airport etc). They are pretty rare, but if you don't want them to spawn either, install this 'vehiclemodelsets.meta' to this location as well:
thank you very much. it worked like a charm