That classic poem by Robert Frost about two roads diverging in a wood had a Pennsylvania moment this week. A state board decided to take the road less traveled, and it promises to make all the difference.

The issue involved vehicles and air quality, always a politically volatile mix in this state -- as the past 12 months bear witness.

In the Legislature, a couple of unhelpful bills were put forward to stop the commonwealth from adopting a California standard rather than a weaker federal rule aimed at cutting back smog related to vehicle exhausts. Their sponsors said Pennsylvania would be ceding some of its sovereignty and new cars would end up costing more.

Fortunately, good public policy appears to have trumped populism. On Tuesday, the state Environmental Quality Board adopted the benchmark California standard by a 16-2 vote for all new cars and light trucks sold in Pennsylvania starting in 2008.

Adopting the California standard may be the road less traveled, but Pennsylvania will have some important company. If the state's Independent Regulatory Review Commission approves the decision within 30 days, as is expected, Pennsylvania will be one of 10 states to go this route. They include big neighbors New York and New Jersey.

On the question of sovereignty, Pennsylvania and other states see their long-term interest in willingly adopting the California standard. And as Kathleen McGinty, secretary of the state Department of Environmental Protection, has testified, it is important to note that Pennsylvania has not adopted the California program in its entirety.

Some environmentalists do anticipate that new vehicles may cost more, although by how much is disputed. At the same time, the new vehicles will travel farther on a tank of gas, leading to offsetting savings.

The wisdom of this decision resides in the state's circumstances. Some 37 counties, including Allegheny, are in the nonattainment category for ground-level ozone. The federal Clean Air Act requires that something be done about this. Since one-third of the state's smog-producing emissions come from vehicles, the choice is making vehicles cleaner or putting the burden on static sources -- like businesses and the jobs they sustain.

This is a no-brainer, and it is one that also will benefit the thousands of Pennsylvanians who suffer from respiratory diseases. Motorists may not like it, but it will make a difference -- perhaps not all the difference -- in cleaning the air. Besides, more people breathe than drive.