The distinct fragrance of automotive exhaust hangs in the air in the parking lot of a popular commercial corner in north Fresno during a recent weekday lunch rush.
Standing between a pair of fast-food drive-through restaurants, one can observe dozens of cars, pickups and SUVs idling in line as drivers wait to order and then collect their food – burgers and fries at one restaurant, chicken sandwiches and fries at the other.
Creep forward a few feet, stop and wait, tap the gas and creep forward again, stop and wait some more – a cycle, repeated over and over throughout the day, from the time a driver enters the line until they leave the pass-through window with their order.
All the while, fuel-burning vehicles pump into the atmosphere a lush combination of hydrocarbons, oxides of nitrogen and other emissions, including carbon monoxide and carbon dioxide – stuff that contributes to the vehicular effluent often known as “smog.”
Just how much gunk is coming from those idling tailpipes?
“Honestly, I haven’t thought about it to that extent,” said Bethany DeGough, a Madera Ranchos resident who sat in a long line of vehicles at the In-N-Out Burger restaurant in north Fresno. “I’ve thought about when we’re walking to go inside the restaurant, ‘Oh, it smells like smog,’ that’s occurred to me.”
In addition to components of ozone or smog, a raft of other tailpipe emissions, such as ammonia, benzene, toluene and more, are breathed in by motorists sitting in drive-through lanes, as well as employees who work the drive-through windows and even other diners inside the restaurant.
Each day, cars line up and idle at roughly 1,300 fast-food and coffee drive-through lanes up and down the San Joaquin Valley. But the extent to which they contribute to the degradation of the region’s air quality is a mystery that appears to have so far gone unstudied by regional and state air quality regulators.
(The number of drive-throughs unofficially inventoried by CVJC includes only fast-food and coffee outlets; it does not include numerous other businesses that provide drive-up or drive-through lanes, such as banks or pharmacies, where vehicles may idle while waiting for service.)
Anyone who’s lived in the Valley for even a few months can attest to the region’s stubbornly poor air quality at certain times of the year. From Stockton and San Joaquin County in the north, to Bakersfield and Kern County in the south, the Valley has long been a “nonattainment region,” meaning it is out of compliance with federal air quality standards for both ozone and PM 2.5 – fine particulate matter about 30 times smaller than the diameter of a human hair that can be inhaled and lodged in human lungs.
Those pollutants and others are often trapped by the mountains that surround the Valley and, under particular atmospheric conditions, turn the region into something that from above looks like a vast, gray lake.
“We know that the amount of fuel that gets burned and the emissions that come out of a gas- or diesel-powered car depends on how fast you’re driving, whether you’re driving, whether you’re accelerating, whether you’re idling,” Chris Cappa, a professor in the UC Davis Department of Civil and Environmental Engineering, told the Central Valley Journalism Collaborative in an interview.
Cappa said emissions from idling vehicles in drive-through lanes certainly contribute to the Valley’s air pollution, but pale in comparison to the total emissions generated by everyday driving on streets and highways.
“On a very average condition, when you’re idling, you might not think you’re using a lot of fuel,” he said. “You’re just sitting there. You’re not moving the whole car, but you’re actually still using on the order of a quarter to a third of the same amount of fuel you might be using while driving the same amount of time. So if you’re driving for a minute versus idling for a minute, you’re still using a good amount of fuel. And that will all add up.”
Why does it matter?
A 2025 report by the U.S. Department of Energy’s Argonne National Laboratory in Chicago states that “idling reduces your vehicle’s fuel economy, costs you money, and decreases air quality. Idling for more than 10 seconds uses more fuel than stopping and restarting your engine does.”
Emissions of carbon monoxide, nitrogen oxides, hydrocarbons and volatile organic compounds generated by gasoline- and diesel-powered vehicles, whether at driving speeds or during idling, contribute to the formation of smog or ozone, according to the U.S. Environmental Protection Agency, while carbon dioxide – which represents about 99% of tailpipe emissions, is a primary greenhouse gas contributing to climate change.
A 2025 study of nationwide fast-food restaurants by industry research firm Intouch Insight determined that the average time a driver spent in a drive-through lane was just over 5 ½ minutes, from entering the line through receiving their order.
The amount of time that a driver may spend in a drive-through lane can vary widely depending on the popularity of a particular location, the time of day, the number of vehicles in line, and other factors. But all those minutes add up, particularly in commercial areas and near freeway off-ramps where drive-through sites are clustered together.
Marcel Moran, an assistant professor at San Jose State University’s School of Planning, Policy and Environmental Studies, and his colleagues have sought to inventory every drive-through in the U.S., from restaurants to banks to pharmacies and more – about 130,000 in all.
“What was interesting to us was obviously the big number, but they also really track with population,” Moran said in an interview with CVJC. “They’re really concentrated in urban places, and they’re very clustered. We found that the average drive-through is something like one-tenth of a mile from the next one, and that makes sense if you think about these kinds of high-speed arterial intersections where drive-throughs seem to be on every corner.”
That tracks with CVJC’s analysis. For example:
- Of 324 fast-food drive throughs in Fresno County, 253 are in Fresno and Clovis; the remaining 71 are spread out across the rest of the county in smaller cities or unincorporated areas.
- In Kern County, of 266 drive-throughs, all but 61 are in the city of Bakersfield.
- In San Joaquin County, of 197 drive-throughs, 96 are in the city of Stockton.
- In Stanislaus County, of 188 drive-throughs, 102 are in the city of Modesto.
- In Tulare County, of 157 drive-throughs, 70 are in the city of Visalia.
- In Merced County, of 89 drive-throughs, 36 are in the city of Merced.
- In Kings County, there are 43 drive-throughs, 26 of which are in the city of Hanford.
- In Madera County, of 41 drive-throughs, 30 are in the city of Madera.
The localized effects of all those drive-throughs are a focus of research by Fengxiang Qiao, a professor of transportation studies at Texas Southern University and co-director of the university’s Innovative Transportation Research Institute. Qiao is one of few researchers who have sought to evaluate how much pollution comes from the tailpipes of idling vehicles when they are queued up in drive-through lanes.
In what appears to be one of the only studies of its kind, Qiao and fellow researchers used specialized equipment to measure the volume of tailpipe emissions per second from test vehicles in drive-through lanes at several fast-food restaurants in the Houston area. That 2016 research shows that pollution levels vary depending on whether a vehicle is idling, braking, coasting, or creeping forward as cars ahead move through the line.
For the test vehicles in the study, an idling engine generated 0.75 grams per second of carbon dioxide, 0.84 milligrams per second of carbon monoxide, 1.04 milligrams per second of hydrocarbons, and 1.71 milligrams per second of nitrogen oxides, a key chemical in the formation of harmful ozone.
The volume of those emissions tick up during a slow coast, when a driver takes a foot off the brake and lets the vehicle move up a few feet to an ordering speaker, payment window or pickup window. Emissions also rise with a slight acceleration to nudge the vehicle from a full stop to the next idle point or to exit the drive-through.
Pollutants: from milligrams to tons
Milligrams and grams per second from a single vehicle creeping or idling in a drive-through lane might not seem like much. At the national average drive-through waiting time of 5 minutes 35 seconds, those miniscule amounts from a single vehicle idling represent:
- 251.25 grams of carbon dioxide.
- 281.4 milligrams of carbon monoxide.
- 348.4 milligrams of hydrocarbons.
- 572.9 milligrams of nitrogen oxides.
The milligrams and grams of invisible tailpipe emissions per second calculated by Qiao from drive-through lanes ultimately add up to thousands of tons of pollutants per year in the San Joaquin Valley.
In an interview with CVJC, Qiao noted that engine technology has improved since his research was done in 2016, but said it still represents a reasonable approximation of vehicle emissions in drive-through lanes. And it’s the incremental and cumulative effects of those emissions, concentrated near a restaurant, that are the primary health concern.
“When my (graduate) student and I discussed this project, we talked about the health issues,” Qiao said. “If you consider emissions, the total emissions from a drive-through site will be very small; however, in the drive-through area and in the restaurant, the emissions will directly hurt human health. People are very close to those emissions.”
The concentration of emissions “not only affect the drivers, it will affect the people who are eating in the restaurant (and) who are passing by the restaurant,” Qiao added. And the workers inside a restaurant – particularly those who are working at the drive-through payment and pickup windows that open and close with each customer, are also being exposed constantly to the emissions.
The California Air Resources Board, the state regulatory agency that oversees air quality rules statewide, does not specifically track or estimate emissions from drive-through businesses.
“It is extremely difficult to accurately break out drive-thru emissions without high-resolution analysis including individual vehicle and location condition information,” the agency wrote in an email response to questions from CVJC. “CARB has worked to reduce all light-duty idling emissions through different technologies such as engines with clean combustion at idle, start-stop functions, hybrid vehicles using electric only at low speeds and zero-emission vehicles.”
But through its EMFAC (Emission Factor) model, CARB can provide an estimate of emissions generated by fuel-burning, light-duty vehicles at very low speeds – under 5 mph. That includes any circumstances where vehicles idle at 0 mph, whether in drive-through lanes, at traffic signals or in highway traffic jams.
The state’s EMFAC model estimates that in 2025, such zero- or low-speed emissions from gasoline-powered, light-duty cars and trucks amounted to:
- Carbon dioxide (CO2): 73,386 tons per year across the eight-county Valley air basin.
- Carbon monoxide (CO): 329 tons per year.
- Reactive organic gases (ROG): 14 tons per year.
- Nitrogen oxides (NOx): 12 tons per year.
“Our assumption has been that extended idling in light-duty vehicles is not as significant as heavy-duty trucks…,” according to CARB’s response.
How many drive-throughs?
One of the problems with seeking to assess the incremental and cumulative effects of emissions generated by vehicles idling in drive-through lanes is that no one is apparently tracking how many drive-throughs there are in the Valley.
In 2017, as the Fresno City Council debated whether to loosen restrictions on where drive-through businesses could locate, the city’s planning staff was asked to provide an inventory of such businesses within the city limits. By the time the City Council member who requested the inventory had left office two years later, however, that information had not materialized.
Similarly, the San Joaquin Valley Air Pollution Control District, which oversees clean-air efforts for the entire Valley region, has no inventory of drive-through lanes. Jaime Holt, a spokesperson for the district, told CVJC in an email that mobile sources of emissions – including passenger vehicles – fall under the responsibility of the California Air Resources Board.
Still, she said, “one of the success stories is that passenger vehicle emissions have been reduced significantly” over the years with the increasing adoption by drivers of cleaner, more fuel-efficient vehicles, including hybrid and electric vehicles.
“As we see cleaner cars on the roads … the impact of idling lessens,” Holt added.
But the counties of the San Joaquin Valley also have some of the lowest rates of adoption of electric or zero-emission passenger vehicles in California. Just over 3% of the passenger vehicles on the road in the Valley (cars, pickup trucks and SUVs) are zero-emission vehicles, while the statewide average is more than double that at 7.5%.
In the San Joaquin Valley, passenger vehicles fueled by gasoline, diesel or other fossil fuels still outnumber those powered by zero-emission batteries or hydrogen fuel cells by more than 30 to 1.
The Valley air district has previously acknowledged the potential impacts of vehicle idling in drive-through lanes. In a 2017 publicity campaign, Fresno County Supervisor Buddy Mendes, at that time the vice chairman of the air district’s board, was featured on billboards imploring drivers to “make a big difference; don’t idle your vehicle.”
Like the Valley air district, the California Air Resources Board does not tally drive-throughs in the state.
But Moran, the San Jose State professor, hopes to change that with his nationwide inventory. He and his colleagues have a paper detailing their efforts under review for publication in a professional journal.
“We feel like we have a pretty accurate and, if anything, a semi-conservative estimate for drive-throughs,” Moran said.
Moran’s work didn’t specifically deal with air pollution impacts, “but obviously that’s one of the reasons we did this study.”
“If you can’t measure the problem, you can’t manage it,” he said. “So we said, let’s try to quantify how many of these there are.”
The National Restaurant Association points out that drive-throughs represent a critical part of business for fast-food restaurants – even as some communities in California, including Napa and Culver City, have either implemented or are planning bans or restrictions on new drive-throughs over concerns about air quality and congestion.
“So to be able to make policy decisions like that, they need to know how many of them there are,” Moran added.
Drive-throughs only part of the problem
“Anytime that we end up with kind of a high density of a particular activity in an area, we absolutely want to think about the impacts that activity will have on the people who live the closest,” said Cappa, the UC Davis professor.
While long queues of vehicles at a coffee place in the morning, or during a lunch rush at a burger joint, may be eye-catching, he said, those aren’t a constant condition.
“We need to think about ‘community average behavior,’” Cappa said. “There will be times when you go by a drive-through and see 30 cars, but there will be other times when you see one car.”
Cappa estimated that the average person spends about 100 times more time driving than they do sitting in a drive-through. Thus, when it comes to reducing emissions, there are other measures that can have a greater impact than limiting new drive-through businesses.
Cappa said he was skeptical when, earlier this summer, the city of Napa’s planning commission proposed a moratorium on new or expanded drive-throughs.
“I find it a very interesting time that such things are coming up as considerations, given that within California – and this will vary geographically – we’re seeing a pretty rapid move towards electric vehicles,” he said. “So it seems to me just odd timing for a focus on emissions from drive-throughs at a time when we’re seeing rapid change in the vehicles that we have that are moving towards no emissions, or at least no local emissions.”
Convenience outweighs concern?
The National Restaurant Association has come out strongly against measures to ban drive-throughs, arguing in a 2023 white paper that the lanes “allow restaurant operators to remain flexible amid workforce shortages while meeting customer desire for flexibility and providing a safe and streamlined environment for their employees.”
The association’s report stated that while those who back bans and restrictions on drive-through lanes seek to reduce pollution and congestion, “for restaurant operators, the bans cut deeply into their operations and sales potential.” The report added that drive-throughs account for more than half of restaurants’ “off-premises” sales – sales of food and beverages that customers order and take away to consume rather than eating at the restaurant.
A nationwide 2025 survey by the restaurant association indicates that 42% of adult customers visit a drive-through at least once a week. The survey also reported that 51% of all adult customers say that drive-throughs are “an essential part of their lifestyle.”
“We do seem to love our convenience, and we equate drive-throughs with convenience,” Cappa said.
During a recent lunch rush at the In-N-Out Burger restaurant at Blackstone and Nees avenues in north Fresno, DeGough – the Madera Ranchos resident – was among several drive-through customers who spoke with a CVJC reporter and said they’ve not really considered tailpipe emissions while idling in the queue.
During her 15 minutes among dozens of vehicles in the drive-through, DeGough said she and her family typically visit drive-throughs twice a week.
“In-N-Out is one of our favorites, so that’s a once-a-weeker,” she said. “If we’re coming into town to get fast-food, In-N-Out is usually the place.”
“We most often do drive-through,” she added. “I have a large family, so typically we’re grabbing and we’re going to the next activity or something.”
Another customer in the In-N-Out line, Isaiah Duran of Fresno, said he only visits drive-throughs “maybe once every couple of weeks.”
“I’m more of a pick-up person,” he said. “I’ll order (ahead) and then pick up.”
Duran said he understands the concern about idling vehicles at drive-throughs, but also questioned efforts to boost electric vehicles because such arguments often ignore the broader carbon footprint of mining the materials needed to manufacture the lithium batteries.
“We don’t look at it that way because we’re not doing it (the mining) here,” he said.
“I feel like people are more concerned about being right than they are about finding a true solution,” he added.
Tim Sheehan is the Health Care Reporting Fellow at the nonprofit Central Valley Journalism Collaborative. The fellowship is supported by a grant from the Fresno State Institute for Media and Public Trust. CVJC research assistant Marisol Herrera contributed to this report. Contact Sheehan at tim@cvlocaljournalism.org.
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