This has been a soapbox of mine for a long time.  There are so many individual things that could be done, but just one of them wouldn't really help much.  The scope of the change necessary to actually reduce (not reduce the growth of) our emissions is virtually impossible.  It is certainly depressing.

In a country that was actually trying to help the environment, not only would hummers be illegal, but only with a relevant business permit would you be allowed to buy any kind of full sized truck.  Cars would have a maximum of 60mph.  All cars.  Auto racing would be illegal.  If you didn't have a family, you'd only be allowed to buy a compact, and drivers' licenses would cost several thousand dollars.  Public transit would be the standard way to get around for anyone who needed to go farther than they could bicycle. 

Sadly, businesses would not be able to afford the kind of delivery schedule they can now, so places like Walmart wouldn't be able to keep anything you wanted in stock at 4AM on Sunday.  We might have to eat more regional produce, and forgo our passion fruit shipped in from the tropics.  The economy would be in shambles. 

It's a bad mess.  It's actually a shame there isn't a god.  It'll take one to fix what we've done.