I used Simple Native Trainer to make this mod.
What I did was place some road barriers around the city, and some construction materials on the roads and in 2 subway stations around the big park.
I am going to do more with this, I just figured I would release what I have so far.
To install, simply place objects.ini in your GTAIV folder, and load it using simple native trainer.
If you already have objects.ini, simply rename it to objects#.ini - replace # with 2 - 9
Let me know what you think, or what you would like to see and I will try to add it!
This is my first mod for GTA in a very, very, very long time.
Also, I will be releasing my bus mod soon. Not only did I get buses in traffic, but they stop at bus stations to drop off and pick people up; I will release it soon, I am making a bus line map right now ^-^