Given the recent court decision that concluded the Environmental Protection Agency had overreached its authority in setting clear-air standards, its plan to consider dramatically tougher emissions standards is brave. It is also entirely necessary.

A federal appeals court last May concluded that the EPA rules effected an unconstitutional delegation of legislative powers – the agency was doing the job of Congress. The line between legislating and rule-making can be vague at times, but in the case of vehicles, there should be little question that all the agency is doing is extending the progress made during the last 30 years of tailpipe improvements.

Specifically, it is extending it toward some of the most popular vehicles on the road these days – sport-utility vehicles, minivans and light trucks. The proposed rules require cars to make substantial improvements, too, but for the first time the EPA is saying that automakers that produce larger vehicles do not have special permission to add extra pollution to the air.

The regulations, which call for tailpipe reductions of about 80 percent, are not going to turn this into a nation of Yugo drivers. First, the regulations are strung out to as far as 2030, with the first real tests for these vehicles coming a decade from now. Second, the EPA gives more time to the larger vehicles to meet them, with the option of trading pollution credits to those who lead in the industry in making improvements. The expected cost of the program when it is completed is an added $100 to $200 per vehicle – about the cost of that added vanity light you didn’t really want in your new car but got anyway.

To help cars run better, the EPA also proposes to reduce the amount of sulfur allowed in gasoline. Higher sulfur levels interfere with a car’s emission-control technology. The EPA proposes to give oil refiners until 2004 to meet the new rule.

What Maine, which already complies with a low-emission vehicle standard, can hope for are cleaner large vehicles and cleaner air that drifts across its borders. Given the amount of time this state struggles with testing emissions and experimenting with gasoline types for more breathable air, the federal changes could make life considerably easier.