One by one they roll onto the football field, accompanied by a hush, and carry the wounded away.

In Week 8 alone, a Toro Workman in Pittsburgh, a Club Car in Arlington, Texas, and Cushman carts in St. Louis and New Orleans scooped up injured NFL players and whisked them out of sight so that the games could resume.

Injury carts are the overlooked workhorses of the underbelly of football. Already this season, they have shuttled dozens of lame players away, including three Green Bay Packers hauled by a Taylor-Dunn cart in a single half. A line judge with a broken collarbone was carried away by a John Deere in Denver. A New York Jets player, after regaining consciousness, was strapped to the bed of a Cushman in New Jersey.

It happens often enough, usually several times a weekend, that “carted off” is football jargon, familiar enough even to fans to need no further explanation.

Injury carts are such a common and longstanding part of football that one with a roof designed like an enormous San Francisco 49ers helmet, circa 1990, currently fronts a sprawling art exhibition at San Francisco International Airport. The display celebrates the history of the NFL and its 32 teams in advance of Super Bowl 50 in nearby Santa Clara.

“Its primary function was medical transportation to safely remove injured players from the field during home games at Candlestick Park,” the museumlike placard below the cart reads. “The pickup truck-style bed allowed players to be transported comfortably while being accompanied by team medical staff. Custom storage areas in the bed provided space for team medical staff to keep various supplies and equipment.”

(The exhibition includes team jerseys, cleats, programs, photographs and other memorabilia, but not miniature versions of helmeted “buggy carts” aimed at children, offered in the Sears catalog in the early 1970s, 3 1/2 inches long with “tough, rubber-look plastic racing tires.”)

Most NFL teams had something similar: a cart with a giant helmet-shaped top, the face mask serving as a front bumper. Last year, an old Vikings injury cart was offered on Craigslist, and a 1980 Steelers cart was recently on the market too. The Denver Broncos still have a helmet-roofed injury cart, now used for marketing, not medicine. Sometimes it trolls the parking lot before home games.

Such flashy injury carts were cousins of baseball’s bullpen cart. For decades, they merrily brought relief pitchers into the game from the outfield bullpen, mostly using a standard cart fitted with a roof shaped like a batting helmet. There were variations — a wheeled tugboat in Seattle, a pinstriped sports car for the New York Yankees, a Harley-Davidson motorcycle with a sidecar in Milwaukee — but relievers preferred to walk or run to the mound on their own. The carts, still seen occasionally in the minor leagues or overseas, were virtually extinct in the majors by the mid-1990s.

By then, NFL injury carts got serious too. Today’s carts are understated and utilitarian, customized for practicality and not festooned for attention. It is curious, in a stadium bursting with advertising and sponsorship messages, to see such restraint on something that moves and that everyone watches. Few injury carts are even painted in team colors. The NFL said cart design was left to individual teams, but the trend seemed to follow the evolving culture around injuries — they are nothing to celebrate.

But the carts are far more advanced than the basic flatbed equipment carts that once scooped injured players off the field when they were not carrying water coolers.

The New York Giants were among the teams that found the helmet-roofed carts impractical and, in 1982, bought their first electric injury cart, according to Ronnie Barnes, the team’s senior vice president for medical services.

Wellington Mara, a Giants co-owner, applauded the idea, finding the cart a more humane method of carrying the wounded from the field than hoisting them over the shoulders of teammates.

Coach Bill Parcells was less enamored, especially when cornerback Ted Watts became a frequently injured rider of the cart in 1985.

“Bill Parcells met our cart and told Ted that the next time we had to go and get him on the cart, he had better be dead,” Barnes said.

Such carts are so ingrained in football culture that even the popular Madden NFL video games have realistic injury carts to carry away the pixelated heaps of hurt players. Until the league asked for a change, the games featured an ambulance that drove recklessly onto the field, running over other players.

In reality, only on rare occasions does the injury cart take a starring role. When Seattle running back Marshawn Lynch was in college at California in 2006, he commandeered a cart for a postgame celebration. In 2011, a driverless cart, its accelerator stuck, plowed into coaches and reporters after a high school championship.

Real injury carts, driven by paramedics or team staffers (in New Orleans, the driver is a retired Saints groundskeeper), are seen as mobile emergency rooms. Most haul medications, intubation equipment and splints. Some have their flatbed divided in half — one side with a chair or two, the other left empty to lie down.

The gray, customized electric Cushman used by the Giants and the Jets at MetLife Stadium has a carpeted flatbed and a reversible front passenger seat that allows a doctor or paramedic to attend to the player in back. Another seat is behind the driver, next to the patient.

There are also two carts, a gas-powered Club Car at each zone, at Dallas Cowboys games. A red one is operated by Arlington Fire Department paramedics; the other, a white one, by American Medical Response, a private contractor.

Which one responds to a call for a cart on the field depends on which side of the 50-yard line the injury takes place, according to Gerald Randall, a battalion chief for the Arlington Fire Department’s Office of Special Events.

Across the NFL, part of the first aid on the field involves persuading a player to get on.

“Today, players vehemently resist riding the cart,” said Barnes, the longtime Giants trainer. “They are usually worried that their families will see them on television carried off by the cart and think something very serious has happened to them.”

Sometimes that is the case. This season, which is about halfway through, more than 160 players have been placed on injured reserve, a designation for those with no chance of returning to play this year.

Many of them were carted off. In those cases, the cart disappears into the depths of the stadium, often to an ovation, and another man takes the place of the injured on the field. The game goes on.