ORCHARD PARK, N.Y. — The show must go through.

For 53 years, there was only one way for the players, stagehands and each piece of their equipment to reach the arena floor, no matter the production. And only one way for it all to come out.

There’s nothing fancy about the Rich Stadium/Ralph Wilson Stadium/Buffalo Bills Stadium/New Era Field/Highmark Stadium tunnel. The dank passageway is purely utilitarian, more Folsom than fulsome. The floor is hard and gray. The walls are cinder block and concrete, painted black and royal blue. Pipes, tubes and ducts span above.

The tunnel is 20 feet wide, nearly 400 feet long and descends at a 7 percent grade — the same slope as Interstate 70 through harrowing Vail Pass in the Rocky Mountains, where runaway truck ramps await 18-wheelers that’ve fried their brakes.

Yet within the tunnel’s austere environment, an ecosystem has thrived since the stadium opened in 1973. It’s chaotic yet organized, gladiatorial yet — usually — tame, a powder keg that somehow stays unlit. Out of spartan necessity, a hive of icons and peons work shoulder to shoulder, producing Western New York’s grandest spectacles.

As cold as it looks, the tunnel pumps life. If not Highmark Stadium’s heart, the tunnel is the aorta from which everything flows. Two games might be all that remain of the uniquely critical artery, with the Bills likely entering the playoffs as a road team.

One shared, narrow tunnel has made for interesting experiences between the Bills and visiting teams. (Tina MacIntyre-Yee / Imagn Images)

The Bills are moving into a $2.1 billion home across Abbott Road next season. Multiple tunnels and a service-level concourse will bring them into the 21st century with a proper big-league venue.

“We are a bit archaic with the one tunnel, and sometimes I forget that because we’ve been doing it so long,” said Bills senior vice president of operations and guest experience Andy Major. “I haven’t seen anything at all comparable to us having every single thing running through that one access point.

“I go to other stadiums, and I’m jealous. But I love our tunnel. There is something special about that tunnel, where if you know the history of this organization and the team, you know every player that’s worn that red, white and blue has gone down that tunnel.”

O.J. Simpson, Bruce Smith, Thurman Thomas, Doug Flutie and Josh Allen are among the 1,148 Bills to have emerged from that tunnel for a home game as Buffalo enters Week 18 with one game left. Joe Namath, Walter Payton, Lawrence Taylor, Bo Jackson and Tom Brady have taken the same route.

Home and visitor locker rooms are directly across from each other, just inside the garage door at the top of the hill. The setup forces enemies into tight quarters, unlike other NFL stadiums.

“Alpha males, especially guys who are Hall of Fame players, you’re eyeing each other down,” said New England Patriots left tackle Bruce Armstrong, who played more road games in Rich Stadium than any other position player aside from Brady and Dan Marino. “The game started before you got on the field.”

The tunnel has welcomed more than NFL royalty, and on New Year’s Day 2008, NHL legends Sidney Crosby, Evgeni Malkin and Ryan Miller starred in the tunnel.

Mick Jagger, Michael Jackson, Bob Dylan, Eddie Van Halen, Jerry Garcia, Beyonce, Jay-Z and Garth Brooks ventured down the tunnel’s runway to perform for crowds that would top 80,000 fans.

The Highmark Stadium tunnel is for the two teams and any vehicles requiring field access, including ambulances. (Tina MacIntyre-Yee / Imagn Images)

Crammed within the tunnel is an armada of service vehicles: ambulances, equipment trucks, field tractors, forklifts, golf carts. When one tries to squeeze past another, tunnel travelers plaster themselves to the walls.

They weave through police officers, janitors, coaches, HVAC repairmen, roadies, referees, outside security guards, doctors, caterers and dozens more, some suddenly materializing from the catacomb offices and dressing areas behind the tunnel’s walls. Major estimated over a thousand people traverse the tunnel at a Bills home game, many of them multiple times.

“There’s a lot of hustle and bustle through one tunnel,” former Bills defensive lineman Kyle Williams said. “A lot of places you come out of your locker room and you make your way down a one-way street. That tunnel is chaos.”

The tunnel was created when the NFL was smaller — logistically, economically, culturally. The business was quaint by comparison. Handoffs drove the game. Athletes didn’t look like they were assembled in a laboratory. Many of them worked side jobs in the offseason to feed their families.

Rich Stadium was no-frills and constructed in 18 months. A single entry point was deemed adequate. The 7 percent slope was necessary to get competitors and equipment down into the lower bowl, dug into 50 feet of shale beneath ground level.

In recent years, every game is preceded by a Bills retiree standing on a platform above the tunnel and “leading the charge” of players running onto the field below. Then the club added chants of “Let’s go, Buffalo!” and “Where else would you rather be than right here, right now?”

When the Bills’ starters were introduced decades ago, they emerged from a tunnel adorned with large advertisements for Miller Lite and Marlboro.

“That’s just hard-nosed, old-school football, man,” Bills cornerback Tre’Davious White said. “Foundational pieces. That era of football, they were probably smoking cigarettes in that tunnel before the game.”

White is correct. Former Bills linebacker Jim Haslett enjoys sharing the story of his first Rich Stadium pregame introduction in 1979. Ahead of him in line was veteran linebacker Isiah Robertson, enjoying a few more drags. Robertson flicked his cigarette at the tunnel wall at the public-address announcer cue and trotted onto the field.

In a more scintillating moment, the tunnel framed Jim Kelly’s jubilant return during his third Bills home game. The 1983 first-round draft pick finally reported to the Bills three years later, once the USFL folded; Buffalo welcomed him with the NFL’s richest contract.

Then, in here-we-go-again Bills fashion, a late hit by the Kansas City Chiefs sent him to the locker room with an arm injury, and backup quarterback Frank Reich promptly fumbled at the goal line. Rich Stadium erupted in the second quarter, when Kelly shot out of the tunnel — Buffalo’s introduction to his warrior spirit.

“You go to all these college stadiums, and everything’s a show,” said Williams, now the interior defensive line coach at his alma mater, LSU. “There’s light shows, smoke bombs and fireworks. To me, the best stadiums you go into are all about the game.

“It’s about a rabid fan base that is loud and letting the other team know ‘You’re in the wrong place.’ Those were always the best experiences.”

(The tunnel does contain one bit of splash. Many people simply walk past without noticing. On a wall next to an elevator outside the Bills’ locker room is a button that triggers “Shout!” from ceiling speakers. The button is disabled on game days to maintain the tunnel dwellers’ sanity.)

Buffalo’s home-field advantage begins within the tunnel’s unfriendly confines. Right off the bus, opponents have emitted countless groans upon walking into the tunnel and making a left turn into the visitors’ locker room, a notoriously basic cubbyhole. About a decade ago, renovations made the space more hospitable, although it’s still considered among the NFL’s worst accommodations.

Just 20 feet across the corridor, Buffalo’s digs have never been considered posh. There isn’t enough room for those trendy accoutrements that have become standard in the big leagues.

At such proximity, eyeballing and smack talking are inevitable.

Armstrong: “That’s where the games started, almost as soon as you walked out of the locker room door.”

Williams: “There’s interactions that happened between coaches to players and players to players from other teams that are probably more colorful than a story will allow.”

Bills safety Jordan Poyer: “Builds a little tension coming into the game. I kinda like it.”

White: “Some guys like to see their opponents before the game. I remember one game against the (Green Bay) Packers. Stef (Diggs) was going against Jaire Alexander. Stef took that moment to get in his face. As a competitor, if it gets your juices flowing to see an opponent, that’s where you meet up and you can get those things across.”

Armstrong: “The mental games were exacerbated when you’re facing each other right away. Buffalo guys are out there sleeveless, and Bruce Smith has all that Vaseline all over his arms.”

White: “I’m not a big trash talker, but I want to see what kind of mindset these guys walk out of the locker room with. What are their mannerisms? What is their body language? I think about it strategically.”

Pregame conflict is easier to duck if you’d rather. Preparations are spread out over hours, dependent on each player’s routine.

Still, when time is precious at halftime or when everybody heads to their locker rooms within minutes of the final whistle, Highmark Stadium’s single artery gets clogged with emotional beasts. Some might be particularly aggrieved. Others may be in the mood to taunt.

“You probably don’t need,” said Williams, “a bunch of grown men who are wired a certain way and competing against one another, brushing shoulders on the way back in.”

Wall of Fame linebacker Darryl Talley had a pregame approach that he couldn’t replicate at halftime or afterward. When he went down the tunnel — for 102 games, fourth all-time behind teammates Andre Reed, Smith and Jim Ritcher — Talley wanted to be last out of the locker room. That way, Talley knew the sounds behind him could come only from an enemy.

“There were a lot of scrapes,” Talley said. He insisted he never got into a tunnel scuffle but that he witnessed too many fights to count. “There’d be a lot of s— going on in there. A guy would do something during the game that wasn’t appreciated, and they’d go up the tunnel and take care of business.”

An infamous skirmish occurred in December 1995, when Bills fullback Carwell Gardner bolted up the tunnel to fight Miami Dolphins linebacker Bryan Cox after they had fought on the field. Cox, hated in Buffalo for delivering a double-middle-finger salute two years earlier, fought Gardner after failing to tackle Thomas behind the line of scrimmage on a game-icing, third-quarter conversion.

Cox was ejected, took off his helmet and milked the exit with a poky stroll. Five times, he spat theatrically toward Bills fans while he walked. As Cox trudged up the tunnel, choosing not to use the portable canopy that would have shielded him, fans dumped beer and trash on him. The South Florida Sun-Sentinel reported a Bills security guard even booed Cox in the tunnel.

Cox had a head start on Gardner, who made a beeline to the Dolphins’ locker room and demanded Cox come out, until security talked him down, albeit briefly. Gardner later went to the Dolphins’ bus to confront Cox again. The NFL levied the year’s two highest fines because of the incident.

Tunnel clashes aren’t limited to players. After his New York Jets won the 1994 season opener at Rich Stadium, first-time head coach and former Bills defensive assistant Pete Carroll ran up to owner Ralph Wilson to yell, “And you’re the guy who fired me in 1984!”

Extra combustible is the presence of officials, who are also wedged into the tunnel. The officials’ locker room is about halfway up the ramp, and they’re not as fast as the players, half of whom are quite possibly unhappy in the moment and feeling jobbed.

“They could have taken the worst end of it,” Williams said. “If things went sideways, you’re damned if you do, damned if you don’t for them. There was a lot of crossfire for those guys because they were in trouble either way.”

The tunnel’s truly Sisyphean tasks have belonged to the equipment managers. Woody Ribbeck spent 37 years navigating that dangerous slope. On the way down, a stuck wheel or a stone could cause a runaway trunk disaster. Headed back up, the chore wasn’t merely dangerous, but also thankless.

Around the two-minute warning, Ribbeck and his crew would begin pushing 300-pound trunk after 300-pound trunk up that hill.

“Some stadiums, you walk out the locker-room door and there’s the field,” Ribbeck said. “With us, we had to carefully go down the tunnel and up the tunnel and deal with all the media and all the workers and families and every Tom, Dick and Harry who knows somebody to get you into the tunnel.

“And you’d think, after doing that six times every game for 37 years, people would know to get out of the way. But they didn’t. I would just go right through them. I had to. I had a job to do or the show didn’t go on.”

The 7 percent grade was rough on players, too, but not necessarily immediately after the game. One might assume the worst walk would come after 60 minutes of harsh physical activity, particularly in Rich Stadium’s first couple of decades. That’s when the artificial turf was thin carpet over concrete, crowned so harshly that those standing on one sideline saw the people on the other sideline from only the waist up.

Williams and Poyer, teammates just for the slump-busting 2017 campaign, agreed the postgame slog up the tunnel wasn’t so bad.

“After the game, once you’ve showered and you get your family, and they all want to go play on the field … Then you’ve got to walk up to the damn parking lot, that’s a walk,” Poyer said.

Williams echoed Poyer’s lament. However, there came a time, about six seasons into Williams’ 13-year career, that he dreaded the trip down before the game. Until Williams suffered recurring Achilles injuries, he said he never considered the slope’s significance.

“The walk down — and this is when we used to warm up on the far end of the field — and then back up the incline aggravated my injuries more,” Williams said. “Those are some of those things that, in the moment, ‘Man, this is the worst thing in the world.’ Now, you look back and some of the tougher times are some of your better memories.”

The clickety-clack of cleats often is drowned out by all the motors, whether the higher-pitched whir of the injury cart or the low rumble of a diesel-powered moving truck. Then there are the piercing backup beeps, a necessity in such a narrow strait, reverberating off the walls.

Snow-clearing vehicles also have to travel through the same tunnel as the players to get to the field. (Tina MacIntyre-Yee / Imagn Images)

You can’t blame Williams, even in the years before he was gimpy, for test-driving a tunnel vehicle or two. He and a fellow country boy once decided to see if they could fire up the John Deere tractors used to plow snow off the artificial turf.

“Aaron Schobel and I were in there one day,” recalled Williams, “and I’m, like, ‘Hey, dude, I wonder if the keys are in that tractor.’ We got it cranked up and started driving it. We were using the hydraulics, lifting that brush up and down. The grounds crew came out, cussing at Schobel and me, told us ‘Get out of those goddamn tractors!’”

The single tunnel is a substantial reason the Bills have been forced to relocate two games to Detroit’s Ford Field over the past 11 years because of snowstorms. Limited concourse widths in the second and third levels contribute to the snow-removal burden, but what slows down the process profoundly is how dump trucks must carefully enter or exit the field level only one at a time.

“Like ants marching to work at the anthill,” Major said.

The new Highmark Stadium boasts several features that should eliminate a relocation snow-nario. Multiple tunnels can truck out snow more efficiently, and there shouldn’t be nearly as much of it. The field will be heated. Most of the seating area will be covered.

Yet, will the Bills’ home lose any of its charm without the tunnel guiding everyone to work?

“The tunnel’s got memories,” Ribbeck said. “Some were good, and some were bad.”

Ribbeck paused for a few seconds.

“But they were more bad than good.”

Williams still has a soft spot. He traveled that tunnel for 87 games, two behind punter Brian Moorman for most in Highmark Stadium, without any in the postseason.

Williams has returned to Western New York a few times since the new stadium has taken shape, and it has been difficult for him to mesh his memories with what will transpire across the street.

“It’s an attack of the senses,” Williams said. “For a decade plus, pulling down that road, it was just a parking lot. Now that thing erupts from the ground. It’s awesome.

“It’s going to be new, different and great, but I think when you tell me to think about the Buffalo Bills and if I close my eyes, that’s where I’ll be — in that old stadium with my teammates and playing the game.”

Williams was asked what he remembered about the first time he ran out of the Ralph Wilson Stadium tunnel for a real NFL game in 2006. As a fifth-round draft pick who made the roster, he was excited enough. Nonetheless, he had arrived from LSU. He played in 92,000-seat Tiger Stadium, which has since expanded to over 120,000 seats.

The Bills’ tunnel didn’t mean nearly as much to Williams until he emerged from it a few months later to witness The Ralph in its full Western New York glory.

“In my mind’s eye, I think about coming out of the tunnel this time of year,” Williams said. “The wind’s whipping, and the snow is flurrying. The sunlight’s starting to dim, starting to fade. You can see the light towers in the falling snow. That scene sticks more in my memory and gets me feeling some type of way that this is what it’s all about.”