Not sure arrest is the right word, but they can do you for being in an unfit state to drive (that means low, and the legal value is below 5.5) – then the DVLA will take your licence away.
1) If you even think you are feeling low, pull over immediately.
2) Take the keys out of the ignition and throw them in the back (legal loophole, you are no longer in control of the car.)
3) Get out of the drivers seat (same principle.)
4) Eat (I always have glucotabs in the glove box and biscuits in the boot.)