Six Flags in St. Louis, Mo. Flickr/Dan

If you want a season pass to Six Flags St. Louis, you’ll have to provide something far more personal than money.

This year it will require your fingerprint, or at least, a “mathematical model” of your fingerprint -- something most Six Flags amusement parks are transitioning to.

That measurement of the minuscule but unique ridges of your digit will be attached to a bar code on the plastic card to get into the park.

At the entrance, pass holders will have to scan both the card and their finger to get in.

It was a bit of a shock to Jason Kirkpatrick, 38, of south St. Louis County, who visited the park with his 3-year-old son and 5-year-old daughter this past weekend. He had to pick his son up so the machine could scan his finger.

It was tough for him to pinpoint exactly what bothered him. Maybe it was just one more sign of the erosion of privacy in modern society. Maybe it was where the information could eventually end up. Maybe both.

“You don’t know what they can do with it. Or more importantly what someone else could do with it,” he said. “It just feels more personal than a photo.”

The technology — dubbed biometrics — has long been in use at other amusement parks, such as Disney World and Universal Studios.

Six Flags St. Louis rolled out its biometric system more than a week ago when the park reopened after its winter break.

Eventually it will be at all Six Flags parks across the country, said Elizabeth Gotway, a spokeswoman for Six Flags St. Louis.

And while other parks say it’s necessary to cut down fraud, Gotway insisted that the new verification system is only being employed because it’s more efficient.

“We didn’t have an issue with that (pass sharing) before because it was easy for us to catch,” Gotway said.

The new system allows patrons to enter the park in less than nine seconds, Gotway said. It also eliminates the time it takes for customers to have their photos taken.

But Kirkpatrick said the new system wasn’t saving anyone time last weekend. The line to obtain a season pass was “as long as I’d ever seen it,” he said.

Gotway said that the fingerprint measurements taken by a computer could not be used to recreate a patron’s actual fingerprint.

The measurements will be deleted from the park’s system as soon as the pass expires.

“This is no different from when they had a season pass with a photo on it,” Gotway said.

When asked if there were any circumstances under which the park might turn over the fingerprint data to law enforcement, Gotway said: “That’s a hypothetical question.”

Robert Niles, editor of themeparkinsider.com, an online consumer guide, said that the use of biometrics at amusement parks is bound to make some people uneasy, especially in light of recent revelations of how much data the National Security Agency is collecting about the lives of ordinary citizens.

“People are naturally going to be concerned about how much privacy they have left,” he said. “But, at the same time, this is how things are going in the industry.”

That said, consumers haven’t mounted any significant protests over the technology.

“Clearly the market has accepted it,” Niles said.

As for concerns that fingerprint data could eventually be sold, it’s unclear who would want to buy it.

“I don’t know if there’s any commercial market for fingerprints at this point,” Niles said.

Indeed, the news that the St. Louis amusement park was using fingerprint technology hardly raised an eyebrow at the ACLU of Missouri, an ardent defender of privacy rights.

“As long as they don’t turn over those prints to the government, we don’t have a problem with it,” said Diane Balogh, an ACLU spokeswoman.

Kirkpatrick said he still would have renewed his pass had he known about the fingerprint scanner beforehand.

“The kids love it (Six Flags),” he said. “I have fun going out there.”

©2014 the St. Louis Post-Dispatch