It made me think deeply about a 1/2 shandy when I drive after the amount that drink and drive .
Found it easiest to have a blanket rule that I dont drink anything alcoholic at all on the same day that I drive. I know it sounds a bit pious but its much easier than making a judgement about how much will trigger the limit let alone then sticking to that quantity.
Had a learning experience some time back, luckily it was in the boat rather than the car and it didnt do any damage. But there was no denying afterwards that the two pints of ordinary bitter that I had had with lunch over two hours had damaged my judgement and made me a bit gung ho. Ran the boat aground.