I'm not talking about the siren sound itself, I'm talking about how the peds react to it. I've seen in an unreleased mod (LCPD mod), that it is possible to modify the siren so that people will pull over properly to the right or the left, depending or where you are on the road.

I'd like to know if there's any mod at all, that does that, or if anyone has a clue how to do something like that. Even if it's something small like, modifying the radius of the siren's effectiveness, that'd be very helpful, because a standard gta iv ped does actually more blocking the moving over. They love to stop in intersections, and they just love to stop on the road blocking like they were cops from the 1980s.

If any of you don't know what I'm talking about here's the video about that LCPD mod:

That was one of the greatest mod I have ever seen! I wish they release it. That was video was posted July 1, 2012! it's already more than 1 year. i wonder why they  aren't releasing it.

It's a really nice mod, but I looks dead. Really old video and no other updates. 

I believe this is his site:

http://lcpdmod.gtaiv.treesoft.dk/Default.aspx

However yeah, it doesn't seem he'll be releasing it. Shame, tbh I'm only interested in that yield thing, or maybe the traffic stops.

 

Anyway so anyone any idea how would I go about modifying the effective radius of the siren?

You could try sending him a PM on youtube asking about it, because he just posted a video 6 hours ago.