So far the best settings for me are (and they still don't provide optimal results on my computer [specs listed below] so far)
AA 0x (anti aliasing, it smooths jagged lines, while mine is set to 0, I really don't see a proportionate drop in FPS by switching from 0x to 4x or even 8x)
Lod 0 (Level of Detail, when you play around with this option sliding it to the left means you don't see as much detail from further away, you can usually see this if you are near to a station and slide it left and right you'll see detail fade in and out.
View Distance 0 (self explanatory really, how far you can see before things fade out)
Effect distance 0 (how far you will see special effects on your screen, lower numbers mean you don't see as far the effects)
Fullscreen Yes (self explanatory, but many games get better performance running in full screen rather than window)
Shadows Off (self explanatory)
Shaders Low (well, low gives better performance than high, but try normal if high is too much for your computer to handle)
SSAO Off (Here I'll just provide a link for the explanation:
http://en.wikipedia.org/wiki/Screen_spa ... _occlusion )
That may get you going.