This results in more ram usage than the 32bit GTAIV was designed for and eventual crashes due to insufficient resources. This is due to the fact that the game has been designed to spawn 500kb sized car models in traffic yet most of the cars in car packs are 6-10 times more detailed at around 3-5mb a model. My rig has an i7, GTX 1080 with 64Gb of RAM, yet even it is brought to its knees when running GTAIV with a large car pack (such as Realistic CarPack 4) and a traffic variety mod (such as Traffic Load or Traffic Flow).
Download link of the original pack itself:
