Help with BaseShaker Setup (maybe Custom effect?)

Hey All, I'm a bit of a newbee and are trying to get my base shaker doing what I want. What I would like is an effect that triggers when on the Concrete kerbs or I'm on the grass only. I have found that when I use the "Road Impact" (the only effect that seems to detect these things) I get all kinds of road nose as well that I don't want. I have tried playing with all the setting and seem to be unable to filter our the road noise. 

Any suggestions as this is the main reason I went to a shaker setup.

With thanks