Thanks for the information - it is always interesting to learn how things are done in other countries.
DWI 101:
In order to stop a suspected DWI driver a PO must have probable cause (speeding, weaving, stop sign violation, etc.)
Currently we have a similar rule to the above - although there is talk of introducing random tests (and lowering limit to 0.05 like most of rest of Europe)
However, the Police are inventive as to how to get "reason to believe someone has been drinking" and asking for a breath test.
One neighbour said he was followed for several miles by a Police car, so, as one would he drove by the book - no speeding, indicating correctly etc to make sure he did nothing wrong for which he could be pulled. He got pulled anyhow.
"You were driving very carefully sir, have you been drinking? Would you mind blowing into this breathaliser?"
Of course, had he not been driving cautiously he would have got pulled for whatever mistake he made.
Another favourite is on the last Friday before Christmas, Police go to railway station car parks to offer commuters returning home from the Xmas party "words of advice on road safety" - delivered, of course, through an open car window and accompanied by several deep inhales of breath to smell alcohol. Again, the slightest hint of alcohol and it is a request to blow into the breathaliser.
They also breathalise anyone stopped for a car fault (even a blown bulb) and all parties after a crash.
Sadly, despite all this, the local paper reports breath test failures going up in the county year on year, with the under 25s in particular being about 50% more likely to fail.
J