The findings are part of an Environmental Protection Agency (EPA) case study that will be released in the coming weeks. The study analyzed the potential air quality benefits of infill development in Charlotte, Boston and Denver.
According to the study's findings, if the rail project can entice 16,500 households and 10,500 jobs to relocate from the suburbs to denser quarters along the south rail line, the overall amount of the two air pollutants that contribute to ozone formation would decrease by one percent countywide. But air pollution from the same pollutants and others would also increase by eight to 10 percent around light rail station areas. The amount of traffic, measured in vehicle miles traveled, would increase by nine percent around the light rail station areas, because more people would live there and many would continue to use their cars for some trips. Others will drive their automobiles to the transit line, then park and ride.
"These are the areas that are absorbing most of the growth," said North Carolina Department of Transportation emissions specialist Behshad Norowzi, who worked on the study. "It would be only logical that you would see increased vehicle miles traveled and increased emission within that specific area that absorbed that additional density."
How significant is a one percent improvement when rail and land redevelopment in that corridor could cost taxpayers hundreds of millions of dollars?
"Let's say you do an overall motor vehicle emission inspection program that targets all automobiles," said Norowzi. "It might give us, in terms of motor vehicle emissions, a reduction of 6 or 7 percent."
Still, Norowzi says an overall one percent improvement isn't insignificant.
"There is no one silver bullet to improve air quality," he said. "Everything we do would count as a step in the right direction."
Norowzi says that the air-choking ozone that plagues Charlotte in the summer won't necessarily be worse around the stations, even though more ozone-causing emissions will originate there. That's because ozone doesn't confine itself to a few streets or a small area, but rather spreads over large areas that cover many square miles, he said.
Charlotte Department of Transportation analyst Joe McLelland, who conducted the analysis, said the slight air quality improvement findings were a surprise to him. Transportation officials hadn't expected that there would be any detectable improvement in air quality.
Despite the good news, McLelland says the main reason a city does a multi-billion dollar transportation project isn't to reap an improvement in air quality, but to provide commuters with transportation options.
According to Charles Lesser & Co. the consultant that did the study from which some of the numbers in the EPA study were derived, achieving the densification needed to make light rail a success along the south corridor transit line could require development subsidies from local government that weren't figured in to the cost of the county's mass transit plan. Where that money will come from is still unclear.
Contact Tara Servatius at firstname.lastname@example.org