Calibration is everything as Ian says, to put it simply if you aren't looking where you are going you will hit something if it stops in front of you the same applies to these guidance systems it won't see what it's not looking at !!

If it's looking in the second lane it won't see a car in the first lane !!! even if that's directly in front of you.

I sat in on a talk about this and the main point was any adjustment alters the calibration.