Utah’s population continues to grow. Unsurprisingly, that means more cars on the road. Yet new data from the Wasatch Front Regional Council and the Utah Division of Air Quality show vehicle emissions are down 73% since 2011.
That little surprise means cleaner air in a state with a bad rap for air quality.
“There's three primary reasons for the decline in transportation emissions,” said Wasatch Front Regional Council Executive Director Andrew Gruber: technology, public transportation and urban planning.
On the technology side, according to the data, even with a 20% increase in population and a 30% increase in total miles traveled by Utahns in the last 15 years, the 73% drop in emissions is due in no small part to the advent of Tier 3 gasoline.
“This is a lower sulfur content gasoline,” said Utah Division of Air Quality Director Bryce Bird. “We saw the initial benefit of Tier 3 gasoline starting in 2017. We found that actually most of the benefit went to the older vehicles.”
The U.S. Environmental Protection Agency adopted new vehicle emissions standards that included Tier 3 gas in 2017. In some cars, it can cut tailpipe emissions by up to 80% — and it’s widely available in Utah.
“Right now, all the refiners and people that bring gasoline into the area are providing Tier 3 gasoline for the entire northern Wasatch Front area,” Bird said. “There's still some refiners that aren't producing all Tier 3 gas, but they are selling all Tier 3 gas here.”
The exact amount of Tier 3 gas available in the state depends on things like seasonal demand and how fuel is mixed before distribution, according to the Utah Office of Energy Development.
The gas typically costs 1-8 cents per gallon more than older fuel, Bird said, but there’s no going back as the new standard takes over. More and more people are also driving fuel-efficient hybrids or ditching gas altogether for electric.
The data is compiled using traffic counts, annual emissions tests required for older cars and vehicle registration numbers in a given area.
“We take all those inputs, and then we put those through an emissions model to look at the daily, hourly, annual emissions from the transportation sector,” Bird said. “That actually results in that number that we produce for each county and then statewide for the projections of actual vehicle emissions.”
New tech is only one piece of the puzzle. Wasatch Front Regional Council Transportation Analyst Fariba Soltani said cleaner gas is just the tip of the iceberg of declining emissions.
“Yes, the fuel efficiency and the technology is a significant part here, but public transportation and more modes of transportation that we are providing for the people, they are also notable and significant contributors here,” she said.
For example, the Utah Transit Authority’s TRAX light rail network in the Salt Lake Valley saw almost 13 million riders last year. The FrontRunner commuter rail running from Ogden to Provo carried over 4 million passengers in 2025. The big commuter train is set for some major upgrades, including a double-tracking project that will increase FrontRunner frequency and reliability, potentially bringing even more Utahns out of their cars and onto public transit.
Additionally, Gruber said modern urban planning has impacted vehicle emissions.
“More cities have walkable centers that have hearts of communities where people can live, work, play, shop with a lower carbon footprint,” he said.
While a 73% reduction in 15 years is amazing progress, air quality experts like Bird think people shouldn’t expect such stellar numbers in the future. Emissions are likely to decrease in the coming years, but there are still factors that could blunt those numbers.
“The population is growing,” he said. “We're building farther from our job centers and so the average vehicle miles traveled on a daily basis is also increasing at greater than the rate of population. But we have some advantages of cleaner vehicles, electric vehicles, public transportation, and things like teleworking that allow people to avoid those trips during the day.”
For someone on the policy front like Gruber, he’s seen more common ground in recent years among different stakeholders who are starting to arrive at many of the same solutions “whether your primary motivating factor is air quality or your primary motivating factor is transportation and traffic congestion.”
He said while collaboration and fewer emissions are great, “we shouldn't just declare victory.”
“Even though the air has gotten cleaner, we know more now about the negative impacts on human health from air pollution.”
