Sorry can't disagree more i love my ABS i can't stop as fast as it can on decent tarmac but in snow i agree no way does it work unless you jump on the pedal then you lock all four wheels and the ABS thinks "oh the cars stopped i'm doing nothing"

Modern ABS systems the main limiting factor is how hard you can push the pedal in a new merc some of them actually sense in an emergency stop and then increase the system pressure to max.

But check out my mechanical answers as one of those might give you the answer. The brakes might be warped giving the feeling of ABS but not actual ABS action.