How will your eyes give you away exactly? New Think! UK Drug Driving Advert

I saw the new Think! Drug Driving advert the other day and I didn't get it. It could be because I don't drug drive or use the drugs that they are referring to but I tried to put myself in the place of a drug user and I really don't think this advert would make me 'think' much about drug driving. I know that drug driving is dangerous and illegal, but if I wasn't already sensible enough to never do it I don't think this advert would really put me off. The oversized eyes of the people in the car are unrealistic so it just makes me think, well, the police aren't really going to be able to see my eyes when I drive past them, as they don't really increase in size like that. Perhaps the tag line 'Your eyes will give you away' is referring to how the police can see the size of your pupils once they've actually pulled you over.  Or perhaps the whole thing is deisgned to cause paranoia in cannabis users, as they will hopefully be too paranoid to drive aftre seeing the ad. I think the whole angle of the advert is wrong though as it only warns you of how you could get caught. There's no mention of the real reason why you shouldn't drug drive, and why it's illegal: because you could kill someone! I just think the advert has no real impact apart from the kind of freaky-looking big eyes, but they just look like a bunch of bush babies in a car.