This Jan. 23, 2013, file photo, shows a poor air quality sign is posted over a highway, in Salt Lake City.
SALT LAKE CITY — Lured by crisp, clean mountain air only a short drive away, northern Utah residents seem to be escaping the murky valley air by driving up the canyons on days when bad air alerts are issued — even though the system was created to limit use of cars, a new study from the University of Utah found.
Ten years of traffic counter data from the Utah Department of Transportation reveals traffic remained steady in the city center, but increased at the mouth of several mountain canyons on days in which state officials issued yellow and red bad air quality alerts, said professor Harvey Miller, lead author on the study. The study spans 2001-2011.
The research shows the trend holds true during nasty winter inversions as well as dangerous summer ozone days. The study is set to be published in the journal Transport Policy.
Similar studies in other large cities such as Atlanta, Los Angeles, San Francisco and Chicago showed no change in driving habits on bad air quality day alerts, said Miller, now a professor of geography at Ohio State University.
But those cities don't have the Wasatch Mountains, home to world-class skiing, hiking and outdoor activities, within a 30-minute drive. The dual message of the alert system — to avoid exposure to bad air but also limit driving — puts people in a predicament, said Miller, who spent 22 years at the University of Utah before leaving in July.
"This is a unique setting where you have bad air quality in the metropolitan area but easy escape," Miller said. "Unfortunately, heeding the public health message by taking that easy escape to the mountains has a negative collective effect."
State officials acknowledge that there have been mixed results since the alert system was created in 1992 for winter inversions, and 2001 for summer ozone. But they say a heightened focus by public officials about the causes of air pollution has led to reduced driving on alert days in recent years not included in the study. Utah Department of Transportation posted more alerts on overhead freeway signs last year and recently created a mobile phone app to advise people of alerts, agency spokesman Nile Easton said.
Northern Utah is coming off back-to back winters of severe pollution in northern Utah, putting an even brighter light on the problem. The intensive media coverage of the nasty winter air seems to have led to a breakthrough with drivers, Easton said. He said the agency's preliminary data from 2012 shows traffic was down 2-7 percent, depending on the area, on red alert days, Easton said.
"I think people now are paying attention," said Donna Kemp Spangler, spokeswoman with the Utah Division of Environmental Quality. "There has been an increased awareness of air pollution and where it comes from."
Miller said the study shows the need for more public transportation in the mountains. While it reveals an interesting pattern, he said the trend needs to be more deeply explored by a detailed, behavioral study to find out more about why people make the decisions they do on these bad air quality days.
For instance, the study was unable to determine if people opted to head to the mountains after seeing the alerts or simply looking outside and seeing the smoggy conditions for themselves, he said.
The Wasatch Front, home to 2 million residents, suffers in the winter through atmospheric inversions, which trap cold air and pollutants in northern Utah's bowl-shaped mountain valleys leading to nation's worst air at times.
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In the summer, residents are warned to be careful about dangers of summer ozone — an invisible gas produced by smog that can tax the lungs of even healthy people. As a pollutant, ozone often goes overlooked, but it acts on lung tissue like sandpaper, said doctors earlier this summer in a news conference warning people to stay indoors during the highest ozone levels. People can still exercise outdoors in morning and evening when the levels drop, they said.
State regulators are currently working on a set of plans to clean up northern Utah's air that are likely to include harsher emissions controls for oil refineries and mines.