!!!IMPORTANT!!!
I shall not provide any support to those who wish to increase the in-game population density count as, in my experience this can lead to frequent game
crashes. If you happen to have alot of vehicle mods installed and have seen them in traffic then, be warned as this may result again in frequent game
crashes.

For those who wish to increase the in-game population density count above normal levels, please read below carefully...

1x traffic & 1x ped = 100% (base)
2x traffic & 2x ped = 200%
3x traffic & 3x ped = 300%
4x traffic & 4x ped = 400%
5x traffic & 5x ped = 500%

* To increase both traffic and ped to 2x, you will need to change the following inside gameconfig.xml
If using Notepad++, locate line number(s) 592 & 593 + 601 & 602 and change the following...
For ped
<AmbientPedsMultiplier_Base value="70"/> to <AmbientPedsMultiplier_Base value="140"/>
<AmbientPedsMultiplier value="100"/> to <AmbientPedsMultiplier value="200"/>
For traffic
<VehicleAmbientDensityMultiplier_Base value="66"/> to <VehicleAmbientDensityMultiplier_Base value="132"/>
<VehicleAmbientDensityMultiplier value="100"/> to <VehicleAmbientDensityMultiplier value="200"/>

If using OpenIV's built-in text editor, locate line number(s) 592 & 593 + 601 & 602 and change the following...
For ped
<AmbientPedsMultiplier_Base value="70"/> to <AmbientPedsMultiplier_Base value="140"/>
<AmbientPedsMultiplier value="100"/> to <AmbientPedsMultiplier value="200"/>
For traffic
<VehicleAmbientDensityMultiplier_Base value="66"/> to <VehicleAmbientDensityMultiplier_Base value="132"/>
<VehicleAmbientDensityMultiplier value="100"/> to <VehicleAmbientDensityMultiplier value="200"/>

If you want 3x traffic & ped | 4x traffic & ped | 5x traffic & ped then, you will need times the stock values by either 3, 4 or 5 to get correct values
only then, you can enter the values and you should now have more traffic and ped in game.