Does public transit reduce pollution?

This article, originally published September 6, 2019 in @theu, was written by Paul Gabrielsen, science writer, University of Utah Communications.

Public transit has long been an answer for people looking to leave their car at home and reduce their air pollution emissions. But now, with better rider tracking tools, the University of Utah and the Utah Transit Authority can better answer the question: How much does public transit reduce pollution emissions?

In a paper published in Environmental Research Communications, University of Utah researchers Daniel Mendoza, Martin Buchert and John Lin used tap-on tap-off rider data to quantify the emissions saved by buses and commuter rail lines, and also project how much additional emissions could be saved by upgrading the bus and rail fleet. The study was conducted in cooperation with the Utah Transit Authority and the Utah Department of Environmental Quality, Division of Air Quality.

High-resolution rider data

Mendoza and his colleagues are certainly not the first to ask how much pollution public transit can save. But a couple of recent technological advances have enabled them to answer the question with a level of detail previously unparalleled.

The first is the advance of tap-on tap-off farecards that provide anonymized data on where those riders who have electronic passes enter and exit public transit. Approximately half of UTA’s passengers use an electronic fare medium. “Now we can truly quantify trips in both time and space,” Mendoza says. “We accounted for all of the 2016 passenger miles by scaling the farecard data, and we know which trips farecard holders make on buses, light rail and commuter rail.”

The second is the General Transit Feed Specification system. It’s the data source that supplies Google Maps with transit information to help users find the bus or train they need. With that data source, the researchers could track where and how often UTA’s buses and trains run.

So, with high-resolution data on the movement of both vehicles and passengers, the researchers could paint a nearly comprehensive picture of public transit along the Wasatch Front.

Balancing emissions

So, with that data, the researchers could quantify the emissions produced and miles traveled of the transit systems (TRAX light rail uses electricity produced outside the Wasatch Front, hence the emissions aren’t in Salt Lake’s air) and balance that with the miles traveled by passengers and the estimated amount of car travel avoided by riding transit.

On weekdays during rush hours, and in densely populated areas, the balance was clearly on the side of reduced emissions. “That tapers off significantly during the evening hours, on the outskirts of the city, and definitely during the weekends,” Mendoza says. In those situations, the number of passengers and how far they rode transit did not offset certain criteria pollutant emissions. (Criteria pollutants are six common air pollutants that the EPA sets standards for through the Clean Air Act.)

For transit to improve its regional reduction in emissions, particularly PM2.5 and NOx, the following strategies, alone or in combination, could be employed: more daily riders per trip, more clean-fuel buses and train cars and/or fewer low-ridership trips.

What-ifs

The current study looks at the bus and train fleet as they are now, with some UTA buses around 20 years old and FrontRunner trains whose engines are rated a Tier 0+ on a 0-4 scale of how clean a locomotive’s emissions are (Tier 4 is the cleanest; UTA is scheduled to receive funds programmed through the Metropolitan Planning Organizations to upgrade FrontRunner locomotives to Tier 2+). So, Mendoza and his colleagues envisioned the future.

“What if we upgrade all these buses, some of them from 1996 or so?” Mendoza says. “They emit a significantly larger amount than the newer buses, which are 2013 and newer.”

What if, they asked, UTA upgraded their buses to only 2010 models and newer, fueled by either natural gas or clean diesel? And what if the FrontRunner engines were upgraded to Tier 3?

Emissions of some pollutants would drop by 50%, and some by up to 75%, they found.

“Now, with this information, UTA can go to stakeholders and funding agencies and say, ‘Look, we’ve done this analysis,” Mendoza says. “This is how much less we can pollute.’”

Mendoza adds that taking transit offers additional benefits besides reducing air pollution. Taking transit gives riders time to read, work or listen while traveling. How does Mendoza know? He’s a dedicated transit rider. “I always get to where I need to go pretty much on time and completely unstressed,” he says. “I almost never drive.”

Find the full study here.

What inspires environmental action?

This is one in a series of stories about a clean air symposium held at the University of Utah on Oct. 3, 2019. The article was written by University of Utah Communications and published in @theu November 8, 2019.

There’s nothing like a crisis to motivate people to change their behaviors.

But when it comes to improving Utah’s air quality and slowing down climate change, action can be taken now to protect the state’s public health, economy and quality of life, according to a panel of University of Utah professors speaking on environmental change.

The panel was one of several presented at the symposium “The Air We Breathe: A Multidisciplinary Perspective on Air Quality.” The symposium took place Oct. 3, 2019, at the U.

Utah has serious air quality problems that “many people try to ignore on a day-to-day basis,” says Tabitha Benney, assistant professor of political science. She said behavioral studies show that a crisis can be “very useful in bringing about environmental change…. Do we want to get to that point? Hopefully, we won’t have to before we make decisions that help us in the long run.”

She is studying what would motivate Utahns to make changes to improve air quality by surveying almost 1,000 people across the state. The goal is to better understand perceptions and misperceptions about air quality, to explain behaviors Utahns take or don’t take to reduce air pollution, to motivate environmental actions and spur policy.

Benney has hypothesized that political orientation, socioeconomic background, religiosity and other factors affect Utahns’ environmental values and beliefs. Preliminary results show that roughly one-third of respondents believe air pollution in Utah isn’t caused by human behavior. And about half of the respondents were unsure if the government should implement policies to solve environmental problems.

While individual actions are important, government policy is seen as key to improving Utah’s air quality and reducing greenhouse gas emissions. That’s why the U’s Kem C. Gardner Policy Institute is studying science-based solutions to both those problems at the request of the Utah Legislature.

Logan Mitchell, U research assistant professor of atmospheric sciences and a member of the institute’s technical team, said the three drivers of air pollution emissions are electricity production, vehicles and buildings. The community should be focused on implementing policies in those three areas, including accelerating the transition to renewable energy and building homes and offices that run on electricity instead of natural gas, he said.

Mitchell said the advisory panel’s final recommendations are due Dec. 13. For individuals who want to take action, he said: “The most important thing as a citizen is to look at those things and let your legislator know you care … and that you’d like to see urgent action that will engender systemic change.”

Panelist Cheryl Pirozzi, a pulmonologist and assistant professor of internal medicine, said the health effects of air pollution would worsen as the temperature climbs due to an increase in wildfires and because warmer temperatures lead to more ground-level ozone. These effects should factor into the cost-benefit analysis of changing policies. She and other U researchers have found that during typical inversions, older adults are about 2.5 times more likely to have pneumonia and three times more likely to die in the hospital with pneumonia.

Still, it was the economic figure in her study that made an impact. The study estimated that reducing air pollution to healthy levels would save more than $800,000 in direct medical costs. The dollar amount “caught more attention than the health outcomes,” she said.

Stephen Bannister, associate professor (lecturer) of economics, agreed that economics is a good motivator for spurring change. “The one incentive that really changes everybody’s behavior is large price differentials,” he said, adding that there needs to be a massive decrease in the cost of clean energy technologies to reduce reliance on fossil fuels.

Selling the public—and the auto and petroleum sector—on the money to be made by moving to clean energy would be a good motivator, according to the panel. Benney said her survey has shown that Utahns, regardless of their age or political party, are more willing to take environmental action when they know one key element: the positive economic benefits of change.

Panelists: Stephen Bannister, associate professor (lecturer), economics and director of the MIAGE Program, College of Social and Behavioral Science; Tabitha Benney, assistant professor, political science, College of Social and Behavioral Science; Logan Mitchell, research assistant professor, Department of Atmospheric Sciences, College of Mines and Earth Sciences; Cheryl Pirozzi, assistant professor (clinical), Division of Pulmonary Medicine, University of Utah School of Medicine.

Moderator: Brenda Bowen, associate professor, Department of Geology & Geophysics, College of Mines and Earth Sciences, and director of the Global Change and Sustainability Center.

 

When it comes to air quality, stick with the simple, hard truths

This is one in a series of stories about a clean air symposium held at the University of Utah on Oct. 3, 2019.The article was written by University of Utah Communications and published in @theu November 13, 2019.

Here’s what Keith Bartholomew tells his students: When it comes to Utah’s air pollution, it’s your job to be simultaneously Chicken Little and Pollyanna.

That mixture of alarm and hopefulness about the future of Utah’s dirty air was clear at the recent symposium “The Air We Breathe,” at the University of Utah. The daylong event focused both on dire data and the need for collaboration between scientists, planners, academics and health professionals.

One of the realities about air pollution is that scientists still don’t understand the complex chemistry of smog, nor the complex mechanisms that lead from pollutants to disease. The flip side is that Utah provides unique “exposure opportunities” to measure those pollutants and study the people affected by it, noted participants in a Scientific Cooperation panel moderated by Diane Pataki, associate vice president for research and professor of biology.

The bad news: “If you live in a place where air quality is worse, your mortality is higher,” said Rob Paine, pulmonary and critical care specialist in the U’s School of Medicine, citing the Harvard School of Public Health’s Six Cities study. “We’ve looked at it a gazillion different ways, and the data is solid.”

Air pollution impacts disease in multiple organ systems—not just the lungs (lung cancer, COPD, asthma) but also bone metabolism, vascular disease, diabetes and depression. “Some seminal work from this valley has shown if you increase PM 2.5 levels by about 10 micrograms per liter, it increases the rate of heart attacks by about 4%,” Paine said. But how pollutants target organ systems beyond the lungs is still a mystery.

To effect change in public behaviors and public policy about air quality, the message should come back, always, to health, he added. “Stick with the simple, hard truths. And say it over and over again.”

Christopher Reilly, associate professor of pharmacology and toxicology, reported that his department has received two NIEHS grants that will focus on understanding the mechanisms that lead from dirty air to damaged health.

Most of the pollution in the Salt Lake Valley is created “secondarily,” after emissions enter the atmosphere, although the chemistry is still not understood, said Jon Lin, professor in the U’s Department of Atmospheric Sciences.

The hopeful news: At the national level, average air quality has gotten better, in large part because of the Clean Air Act. “It shows there is action you can take to improve air quality,” Lin noted.

At the macro and micro level, improvements to city planning and building construction can make a difference too, said Bartholomew, associate professor in the Department of City and Metropolitan Planning.

“Transportation is now the single largest sector of the economy leading to air quality problems,” he noted. On the macro level, increased housing density leads to a decrease in car use. On the micro-level, sheltered bus stops instead of the “pole in the puddle model” have led to twice the number of riders compared to a control group.

The U’s scientists need to work together to solve Utah’s bad air, the panel agreed, rather than working in their individual silos. “Gatherings like this,” said Reilly, “need to be a lot more frequent.”