Neat idea, but...

Does anyone really call is by those names? I use weed (cannabis), E (ecstasy) and Crank (Speed). I mean, the street slang I'm told is this. Maybe it's different in Oz?

This seems aimed at parents rather than those driving on drugs. Also, does Ecstasy make you delusional? And I would have thought cannabis made people forget where they were going or why they were driving? That might make a better execution for some kind of GPS routefinder. Haha.

I guess there's plenty of nicknames for the stuff, depending where you are. I mean, I talk about weed, but the kids round here call it 'draw'. Ecstasy is simply 'pills'. Speed is 'whiz'. Better to stick to the generic names.
As for the campaign, well, lorry drivers have used speed since time immemorial. They don't kill a lot of people, really, but I guess in Australia it's the roos that have to watch out on those long drives. Cannabis isn't so bad to drive on, as long as you check your speedo to make sure you're still moving, and don't stop at too many service stations for chocolate. Ecstasy is a bit of a worry, but surely most people have better things to do than drive when they've had a pill. Like hugging people and gurning.
Hunter S. Thompson would have sneered.

There are all sorts of names for various drugs - Speed dates back to the late 70's ("Speed Kills" was a grass roots anti-drug poster of the time). Back then, Methamphetamine was the only kind of speed (too much buzzing in your head for me). Cannabis is the proper genera name (Cannabis sativa is one species) for weed, pot, funny cigarettes, chronic, doobies, wacky weed***, dope, etc. Ecstasy, or "E" or "X" is a strange one - it breaks down inhibitions (and brain cells), and everything gets touchy-feely, and loose (in guys, this is often a problem, usually solved by taking Viagra with your "E" [of course, one way for guys to 'get some' is to pretend to take the "E", and wait until it affects the girls]).

Speed is probably the most dangerous of the three in terms of driving (and possibly in terms of health - excluding driving). Your sense of time is very distorted, as is your sense of what you can do in a particular amount of time. Pot also distorts your timesense, but not necessarily as badly as speed does.

I agree with Alex about "E", you usually have better things to do than driving.

*** At one point in my life, I thought that Locoweed was another name for pot, but I've since learned that Locoweed is actually datura naturi, or Jimson weed. Check out books by Carlos Castenada for his exploration of that drug, along with others, as he learned how to become a brujha.

Note that all of this (including spelling) is from memory.

Jimson weed, nasty stuff, extremely poisonous. Part of the nightshade family, very closely related to tomatoes.

There's a case on record of a family who grafted tomato shoots onto jimson weed in an attempt to make the plants hardier and the tomatoes bigger. It worked. Then they ate the tomatoes. The entire family died at the dinner table.