Following this week’s subway shooting attack in Brooklyn, Mayor Adams has suggested adding weapons detection systems to the city’s stations. However, there’s no reason to believe that these expensive systems would make the subway safer for the average rider.

“I don’t think metal detectors would be practical: You’ve got to move hundreds of people in and out of stations — people are not going to wait in line to be searched by a metal detector,” a transit safety analyst, Nicole Gelinas, told The New York Sun.

The mayor told WNYC that the city has “identified several new technologies that are not like metal detectors that are used at airports, where you have to empty your pockets and go through a long line to get in.” 

He added: “You just walk normally through the system. It is not even detectable that the devices are there. And we think there is some great promise in this technology, and we are going to continue to explore that.”

Whatever sort of “innovative technology” the mayor was referring to, it would likely be prohibitively expensive.

Mr. Adams’s press secretary, Fabien Levy, told the Sun: “Some technologies we’re looking at are already being utilized across New York City — in ballparks, at museums, and at hospitals.” 

He added: “Mayor Adams has made clear that public safety is his top priority, and he is willing to test and analyze numerous forms of technology in a legal, responsible way to protect New Yorkers.”

Although Mr. Levy made clear that the machines in question are not the walk-through metal detectors that most people are familiar with, they do provide a useful comparison.

Assuming the average cost of a walk-through detector would be about $3,000 each, adding a single device to every station would cost $1.4 million. That’s just one for each of New York’s 472 stations, meaning we would likely need considerably more, in addition to an officer of some sort to actually run the security check. Detectors alone wouldn’t stop anything.

The more modern “innovative technology” would be priced and financed differently. One company that provides weapons detection systems is Evolv.  A company representative said products are sold in a subscription model and that the price varies based on the complexity of the system.

Regardless of cost, Mr. Adams doesn’t have the authority to implement such a policy. The MTA is a state-run agency and any change this dramatic would require action by the agency’s 21-member board.

While the mayor nominated four members to the board, the governor and suburban county executives also have influence over the system and its yearly recurring costs.

Technical details aside, there has been an almost unanimous chorus of opposition to the idea, from the New York Civil Liberties Union to the libertarians at Reason magazine.

Ms. Gelinas was doubtful that a system of metal detectors would do much of anything to prevent a terror attack like the one in Brooklyn.

“It is a mass terror event and it is very difficult to stop,” she said. “It is very different than the chronic low street-level crime.”

“One thing to keep in mind is the risk of terror attack is low,” Ms. Gelinas added. “We are not going to build a subway system around the risk of terror attack.”

Although attacks like the shooting in Brooklyn draw wide attention, low-level crime is what plagues the subway and affects its millions of riders every day.

Last month, crime in the city was up 37 percent compared to March 2021. According to the NYPD, major transit crime was up about 53 percent. Despite the mayor’s Subway Safety Plan, announced earlier this year, the subway apparently is getting ever more dangerous.

In the words of Ms. Gelinas, the plan “didn’t do anything to decrease violent subway crime.”