– On a rooftop 18 stories above a busy street, it’s 16 degrees, the wind’s blowing and a bunch of bundled-up guys want to see what some might call a monument to madness.

There it sits atop the old building on Independence Avenue: a Chrysler Victory Air-Raid Siren. Twelve feet long and 3 tons. If Soviet missiles had ever headed this way, somebody would have fired up its V8 hemi engine and blasted 138 decibels over 25 miles.

“They must have found a deaf guy to operate it,” Stephen Bean, a coordinator with Kansas City’s emergency management office, yelled to the others as they looked at the siren that had a hand-operated lever.

If Kansas City ever has a snafu like Hawaii did regarding an alert about an inbound missile, the culprit won’t be this old siren atop Hardesty Self Storage, which used to serve as the Kansas City U.S. Army Quartermaster Depot.

But city officials do have a plan for a nuclear detonation. And it’s not the same as during the Cold War.

The biggest threat now is not from a nation state, but from terrorist act. That makes planning a response more difficult. The Soviets likely targeted military installations and defense plants as part of an overall military strategy.

“The target now may just be crowds and that can be anywhere,” Bean said.

Among the reasons for concern: terrorism, unstable regimes, unstable leaders, rogue groups and the possibility of stray nukes.

“We are facing a threat of a nuclear detonation, and not a dirty bomb, but a substantial nuclear explosion from North Korea or a rogue terrorist group,” said Irwin Redlener, a Columbia University professor and public health activist. “Someone stealing a bomb is perfectly conceivable. But not a single city in America is prepared for such an explosion.”

Kansas City officials would dispute that. They’re not on high alert at the emergency command center, but they were recently. The last time it was fully manned was in August, for the total eclipse.

The siren is a Cold War relic now. Rust, bird poop, rickety ladder and chicken wire, up there since the 1950s, little more than a reminder of a time when every kid in America knew “duck and cover.”

There used to be three others like it around the city. Now and then, somebody offers to buy this remaining one.

“We ask them how they plan to get it down and then we never hear from them again,” said Mike Riccitiello, a Hardesty Self Storage manager.

The recent visit by Kansas City emergency management officials to the rooftop was nothing more than a curiosity field trip. But it came the week after the Hawaii alert.

Calls are growing across the country to dust off the nuclear attack response protocols and evacuation plans that every city once had.

The collapse of the Soviet Union in 1991 ended that diligence — the Cold War was over. That peace of mind lasted about 25 years. Now, the world has changed again.

Michael Scheibach knows a little about this. He turned his doctorate dissertation into a book: “Atomic Narratives and American Youth.”

He remembers when every city in America had an evacuation plan that told people where to go, which streets would become one-way, train schedules and which streets would be dedicated for emergency vehicles.

“We are to a point where the subject needs to be revisited,” Scheibach said. “I know parts of country, mainly the West Coast and Hawaii, are looking to re-implement evacuation and fallout plans.”

He, too, thinks the biggest threat does not lie with old Cold War foes. “Russia, China and the U.S. are too invested in stability of the world,” Scheibach said. “It’ll be North Korea or a terrorist group.”

Brooke Buddemeier, a health physicist and radiation expert at Lawrence Livermore National Laboratory, is currently working on models of low-grade nuclear detonations. He thinks the delivery method would be a delivery truck instead of a missile.

“The response, outside the blast zone, would be very much like for a tornado,” Buddemeier said. “Get indoors, avoid all the particles that are going to land on rooftops and the ground. Stay there.

“A little bit of knowledge can save a lot of lives. A city could prevent 250,000 deaths.”

That’s the plan for Kansas City’s office of emergency management. Inside the control room on a recent morning, a large screen showed a nuclear explosion simulation. Circles indicated the blast radius, second tier and third tier. The immediate job is to section off the city. Hospitals would be cleared of anybody who doesn’t have to be there.

“We go into mass casualty phase,” Bean said. “Half the people may be dead, but we still have to help” the rest.

In 1970, the Kansas City area cooperated on a community shelter plan for people to follow in case of nuclear attack. Part of it was a list of hundreds of fallout shelters, sometimes three to a block.

That was Cold War thinking. Now, the plan is to tell people to get inside and stay put. After a blast, dirt, dust, debris go up and come back down.

James Connelly, Kansas City emergency manager, said the city’s response would be based on blast site and prevailing winds. There are 129 sirens around the city, designed for tornado warnings, but they can become civil defense sirens.

Software would map the response. “Then we will tell people what to do and where to go,” Connelly said.

Just off Interstate 70 sits a building with no name. Inside, two guys are putting finishing touches on a bomb bunker.

“It’ll withstand anything but a direct hit,” said Ryan Olah.

Olah, 33, is in charge of manufacturing for Defcon Underground Manufacturing. He and his partner, Cory Hubbard, 35, had an idea a couple of years back to make underground bomb shelters.

They have sold a “handful” of the shelters, which sleep a family of four and come with bathroom, shower and radioactive air filtration.

A typical bunker is 8 feet wide, 8 feet high and 20 feet long. It is designed to be put in the ground with 3 feet of dirt on top. “You’re not going to live in this thing for 10 years, just until things calm down,” Olah said. Price: $100,000.