I think it was something that wouldn't work in freeplay, only in missions....Or something like that.... I may be wrong, but there was a discussion about a while ago. Edit:
Well, if he wants to reduce his traffic, he'll have to live without multiplayer. Just 'Print Screen' on it's own, then in paint or something similar 'CTRL' + 'v'.
I looked through the files: <vehicletraffic factor="2.0"/> (In 'freeplayparameters.xml') There are loads of different timezones but change the number, lower, in each. Not sure if it will work as I haven't tried it.
I don't get it, everyone else always gets traffic issues and I never get any. The thing I occasionally get is a patrolling police car that gets stuck and that's easily solved.
The law may be different in the Netherlands, not stopping at the scene of an accident (incident) is an offence in the U.K. if witness anything you must stop and wait for police to arrive and take a statement, I knew someone who didn't stop they got a £500 fine and 6 points on their driving licence.
You need to edit the security of the file. For me it would be: Right click, Properties, security, edit, choose my user, tick the boxes (In the allow column).