Traffic Police has started to deploy the ring-fence roadblocks around cluster of pubs (see news article on Today). This is my favourite poster on Drink Driving - the message is clear: When will you have had too much? You can't calculate your alcohol limit, so don't try.
Update July 10, 2009: Sorry folks! The image of the cool poster has been taken down by the site keginabox. Just imagine this scene in a bar and the image of a less-than-half-filled beer glass with the beer foam nicely lining up one side like the markings of a ruler. I can try to draw it if there is enough demand *LOL*.