Georgia Gov. Roy Barnes (D) is close to reaching a compromise with environmentalists who have sued state and federal agencies over air-quality concerns and kept metro Atlanta’s $36 billion transportation plan on hold. To improve air quality, Barnes has proposed speeding up a $4.5 million study of the health effects of the city’s air pollution, moving more quickly to construct high-occupancy-vehicle lanes, and creating stricter standards for diesel engines and utility equipment. An attorney from the Southern Environmental Law Center, representing several environmental groups, said the groups had agreed in principle to the settlement offer, but they were reluctant to walk away from previously filed suits over air quality, including a case now before the 11th U.S. Circuit Court of Appeals.