This is what my mate Dave said on the matter:

"Hey! That's funny, I've already bought one of those and tested it!

I got into the new Nissan after a night out at a bar and tried to drive it

home. It subsequently told me that I was too drunk to drive and that I

should get back into the bar and finish chatting up a the bird I had left

there, and then get a taxi home with her!

Wow, what f**king great technology - it worked a treat for me!"

I hope this finally puts an end to this pessimistic debate.