We have been traveling lately and just discovered a new feature that many complained about (me included) with the split screen showing the off-ramps on the right and the smaller map on the left while on the freeways. There is now a small button with a split screen icon just to the left of the right off-ramp screen when pushed removes the off-ramp screen and returns the map to full screen. pushing it again restores the split screen. Nice feature for those that don't need or want the off-ramps to show! Button only visable when on the freeways!

 

Yep,
It works the same way in my 07 escalade, but as you said it's only on a highway.