programming ABS on dangerous surface

Hi,
tried to figure out some kind of ABS for cars when driving on planet but there seems to be missing some things like changing to max. speed when you do not need ABS, this is a bit frustrating, e.g. I need inputs for pitch while I am using pitch itself for controlling the surface velocity on dangerous surfaces like mountains.
on start
while true
if input pitch > 0
display "normal fast mover"
set Brake to 0
if input Pitch <=0 then
display #ABS#
if velocity Surface <= 9 then
set Brake to 0
if velocity Surface >= 10 then
set Brake to 1

what is missing here: I cant use pitch = 1 in the lower display ABS section because if I do this, then I will never enter this ABS subroutine again ;-/

But I want fast speed for e.g. low terrain to fire engine to the max and when all time low moving over hills, there should a steady big limitation in speed. I tried several other solutions but cant find a proper one.