A tantalizing perfume engulfs a corner of City Hall's sprawling plaza one Thursday afternoon: chicken, lamb, exotic sauces, and pita bread, coupled with the smoky aromas of ribs and grilled cheese.
It's coming from the Chicken & Rice Guys food truck, sitting less than 20 feet from a friendly competitor, Roxy's Gourmet Grilled Cheese. The smell overwhelms any aroma coming from restaurants nearby, luring more than 60 people — some in tailored suits, others in Red Sox jerseys — to quick and cheap meals emerging out of well-worn trucks.
Why, in a city with eating options ranging from burgers to Vietnamese pho, do hordes of people voluntarily stand in 15-minute-long lines for bowls of rice and meat or grilled cheese?
"It's better food," said Curt Ege, a software specialist at Fidelity Investments who said he eats at food trucks three times a week. "It's the same old stuff over there."
Ever since the introduction of a Korean taco truck in Los Angeles in 2008, food trucks have exploded in popularity, some boasting top chefs who appear on the Food Network. The sensation has even prompted academics to spend years analyzing the trucks' success, with sociology doctoral students from Northwestern University and the University of Michigan detailing the rise and transformation of gourmet food trucks in a study presented Saturday at the meeting of the American Sociological Association.
By melding highbrow and lowbrow foods, food trucks have not only emerged as one of the city's and country's most popular dining options — they've helped bridge socioeconomic gaps.
With gourmet-style dishes at fast-food prices, they attract customers ranging from train drivers to Nobel Prize laureates, said Daphne Demetry, a doctoral student at Northwestern and one of the study's authors.
"We're changing the way in which we eat and how we eat," Demetry said. "Food trucks used to be called 'roach coaches,' and now they're serving elite food."
The study's authors harvested Twitter data to figure out how many trucks were in each city and then reviewed the trucks' online bios to begin assembling a profile of food-truck culture across the country.
There's no single factor that explains the trucks' popularity. The researchers found that cities with fewer fast-food chains and a diverse, highly educated population tended to have the most food trucks. High rental costs in larger and more-spread-out cities also led to more trucks because they offer a cheaper alternative to opening a restaurant.
Boston's food-truck scene — which ranked 50th nationwide in 2012 in the study's analysis of the number of trucks — began with 15 in 2011. That number has climbed to 68, with several more expected to open this fall, said Edith Murnane, director of the city's Office of Food Initiatives. Boston also has a mobile food truck committee dedicated to improving and protecting the restaurants on wheels.
More people are eating out in Boston and are spending more money on food than three years ago, Murnane said, though she's unsure whether that's a direct result of the growing presence of food trucks.
Part of the phenomenon stems from the unorthodox menus, Demetry said. While traditional brick-and-mortar restaurants might shy away from mixing ethnic dishes, food trucks embrace fusion. That can mean mixing Southern and sushi, or macaroni and cheese — a traditionally lowbrow comfort food — with exquisitely prepared filet mignon.
Boston's Roxy Gourmet Grilled Cheese aims for that kind of fusion. It offers a traditional grilled cheese, called the Rookie Melt, with Vermont cheddar cheese and tomato. Then there's the Green Muenster, one of its most popular items, with applewood bacon, guacamole, and muenster cheese.
Despite their popularity, food trucks have raised health concerns: A Globe analysis last year found that 41 percent had been cited for food safety violations that put customers at risk of food poisoning.
But inspectors visit the trucks two to three times a year, compared with once a year for restaurants, and usually find only minor violations, Murnane said. City officials also work with the truck operators to help them meet expectations.
Open communication between customers and food truck operators helps build a loyal customer base, the study found. Twitter and Facebook accounts broadcast the day's menu and where trucks will be, and many companies seek direct feedback from customers to better shape their menus.
For instance, the all-vegetarian Clover, with six trucks in and around Boston, invites customers to food development meetings, where chefs experiment with recipes to update the menu. One customer's suggestion prompted the company to temporarily offer a Sicilian sandwich in addition to its traditional chickpea fritters, heirloom tomato sandwiches, and fries.
"We don't have any ethnicity we're tied to," said Lucia Jazayeri, the company's communications director. "We'll do any type of culture as long as it fits into the type of food we do," which is primarily sandwiches and fries.
Clover boasts that it does not have a freezer and cooks food fresh each day, making it an appealing and fresh option. But it was forced to temporarily shutter all its restaurants and trucks last summer after a salmonella outbreak sickened more than a dozen customers.
Since October, it has passed all of its health inspections, some with minor violations, according to city records.
The success of the Chicken & Rice Guys is rooted in how quickly it gets food out the window, said Johnny Nguyen, a senior manager. Employees prepare meals about three hours before lunch offerings begin at 11 a.m. and grill the meats on site.
The truck has not passed two of its inspections in the past year, but it passed its most recent in February, city records show.
"Speed is really important. During lunch, we know people only have a short break," said Nguyen, brow dripping with sweat from grilling meat all afternoon.
While Boston has yet to reach the food truck status of, say, Los Angeles or Portland, Ore. — which ranked first and third, respectively, with 366 and 168 trucks in 2012 — some of the city's food trucks have enjoyed enough success to open restaurants.
Clover has opened five brick-and-mortar destinations since its truck debuted at the Massachusetts Institute of Technology in 2008. Chicken & Rice Guys is in the beginning stages of opening a restaurant. Roxy's Gourmet Grilled Cheese opened a brick-and-mortar on Memorial Day.
And several more trucks are expected to debut this fall, Murnane said.
"The real question is: How long is this going to last?" Demetry said. "It's becoming more than a way to simply get lunch. It's a phenomenon."
Yasmeen Abutaleb can be reached at firstname.lastname@example.org.