hong kong USAJAPANunderdeveloped countries
Under the Federal Clean Air Act : California, has the most stringent emissions standard.
United states
They are based on the California State vehicle emissions standards, which are the toughest anti pollution requirements in the USA. Vehicle/ after market manufacturers produce cars and performance components to meet the Californian emission standards. Hence, fifty state legal..
Foreign car manufacturers will have to meet those emission standards on cars they export to the U.S.
Scotland and Ireland
Currently Euro2, according to ECE R83
No not as long as they meet the smog emission standards and the safety standards set by the state.
Depends on what sort of vehicle your driving, but most of them are to EU regulations. You can check them out at this website; http://www.dieselnet.com/standards/au/ and because you wont know what the EU standards are, you can check them out here; http://www.dieselnet.com/standards/eu/ld.php But can't seem to find any recent emission standards on motorcycles. Hope that helps you out anyways. ;)
Cali has the toughest emission laws in the USA, and as with other states, they have to follow fed guidelines, but can impose even more higher standards above and beyond the feds, and Cali does, so I would suggest that you bring your vehicle up to Cali standards, or it will be just a matter of time before they test it.
Tighten emission control standards for factories and automobiles.
Yes, but it must meet US safety and emission standards.