My factory radio supported this and my z150bh is hooked up to the VSS cable (info screen shows speed pulse working great). However it doesn't seem to increase or decrease the volume as i get on/off the highway. I thought this unit supported this feature and i can't find anything in the options to modify this nor anything in the manual. Does it support this? 

My factory radio supported this and my z150bh is hooked up to the VSS cable (info screen shows speed pulse working great). However it doesn't seem to increase or decrease the volume as i get on/off the highway. I thought this unit supported this feature and i can't find anything in the options to modify this nor anything in the manual. Does it support this? 

No, it does not.

I don't know why they don't offer this as a feature. Since it's able to calculate speed, you would think it would be easy to implement. And as a driver of a convertible, it would be greatly appreciated.