Why don’t theme parks build more year-round haunted houses?

The bloodcurdling screams and spine-tingling shrieks emanating from haunted mazes and scare zones during Halloween season mark the busiest time of the year for the nation’s theme parks outside the traditional summer months.

Which raises the question: Why not keep a haunted house open all year long?

Virtually every major theme park chain now stages some type of Halloween event, with many offering elaborate mazes haunted by ghosts, zombies and killers of every stripe. But very few parks extend the haunting outside of October. If Halloween is so wildly popular one month of the year, why not stretch it out to the other 11?

Over the past few weeks, we learned that one year-round haunt would close for good while another would soon open its menacing doors.

This Halloween brings to an end the House of Horrors year-round maze at Universal Studios Hollywood, which operated under several guises during its 15-year run. The two-story walk-through haunted house has been home to mummies, vampires, grinches and even chickens.

Next year, Canada’s La Ronde amusement park will debut the Maison Rouge: Labyrinth of Terror year-round haunted house. The rotting funhouse infested with evil clowns will be designed by a Montreal-based scenic shop that has worked on Cirque du Soleil and Cavalia shows.

While many theme parks have dark rides, tilt houses, mirror mazes and carnival funhouses, fewer and fewer parks operate year-round walk-through haunted houses or dark mazes with live actors.

In North America, year-round haunted houses can be found at only a handful of smaller amusement parks, among them Dr. Frankenstein’s Haunted Castle at Indiana Beach, Vampire Infestation at Six Flags Mexico and Pirate’s Cove at Pennsylvania’s Waldameer.

You’re more likely to find year-round mazes at seasonal seaside parks in the United States, such as Ghost Ship and Curse of the Mummy 3D at Morey’s Piers on the Jersey Shore, Fright Walk at Santa Cruz Beach Boardwalk and Pirate’s Cove at Maryland’s Trimpers.

To be certain, plenty of independent haunts operate in the United States: Times Scare (New York), Legends Dark Amusements (Florida), Fear City (Illinois) and Sinister Point (California).

Merlin Entertainment, the parent company of Legoland parks, runs a chain of Dungeons in England, Scotland, Germany, the Netherlands and San Francisco. Ripley’s Haunted Adventures operates in South Carolina, Tennessee, Texas and Thailand.

Halloween attractions generated more than $300 million last year in the U.S., according to the trade group Haunted Attraction Assn. So why aren’t more year-round horror attractions found at American theme parks?

Haunted houses are more popular at overseas theme parks where Halloween is still a relatively new tradition.

In Europe, you’ll find the Krueger Hotel at Spain’s Tibidabo, Phobia at Italy’s Mirabilandia, Kammokuja at Finland’s Linnanmaki, Horror House at Italy’s Movieland, Spokhuset at Sweden’s Grona Lund and Spookslot at Efteling in the Netherlands.

The Pasaje del Terror at England’s Blackpool Pleasure Beach employs 18 “scareactors� in a series of 20 theatrically designed sets with sound, lighting and special effects.

Hocus Pocus Hall at Chessington World of Adventures outside London uses animatronic figures and video projections to pump up the fear factor.

And at Liseberg’s Gasten Ghost Hotel in Sweden, you can check out any time you like, but you can never leave.

Asia is equally in love with the recently imported Halloween tradition. Japan’s Yomiuriland features the Haunted House Mukuroya while China Dinosaurs Park has the neon-lit Fantastic Spooky House.

The Super Scary Labyrinth of Fear at Japan’s Fuji-Q Highland takes “patients� on an hourlong journey through a haunted hospital, including a quarantine ward, operating room, bacteria lab and mortuary. It’s not unusual for the year-round maze’s wait time to reach four hours.

Indeed, almost every major Japanese theme park has at least one if not two haunted walk-through attractions -- either with or without live actors.

With the success of Universal Studios movie theme parks’ turning classic and contemporary horror franchises into haunted mazes during Halloween, theme parks around the world have begun experimenting with brand-name, year-round haunted houses.

Spain’s Parque de Atracciones converted the year-round El Viejo Caseron maze into the Walking Dead Experience just in time for Halloween.

Thorpe Park in England paired a Saw: Alive year-round maze with the 2009 Saw coaster for a few years before interest waned. (It didn’t help that a fire broke out in the maze).

In recent years, New York-based Sudden Impact has built temporary branded mazes at parks around the world that operated outside the Halloween season, including Prison Break at Australia’s Luna Park, Terminator at Canada’s La Ronde and Alien vs. Predator at Australia’s Dreamworld.

So why don’t more U.S. theme parks operate year-round haunted mazes?

The answer usually boils down to one of two reasons: Cost and tradition.

It takes a lot of people to staff a haunted maze. During the Halloween season, some parks assign as many 40 employees to a single maze -- serving as monsters, ushers, security and supervisors. That becomes a very expensive proposition when the popularity of a year-round maze declines over time -- as it inevitably does.

And as Americans, we frown on our holidays seeping out of their designated seasons. We don’t want Christmas lights up after the first of the year, turkey dinners during Spring Break or skeletons before school starts.

Combine those two factors with concerns about cannibalizing a Halloween season that has become a cash cow and you can see why U.S. theme park’s like to keep haunted mazes confined to the month of October.

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