The NYPD’s multi-agency training exercise that simulates a dirty bomb attack on New York City is entering its fourth day Friday.
On Thursday, police, FDNY and Coast Guard vessels managed to find a mock dirty bomb aboard a boat near the Verrazano-Narrows Bridge.

Friday’s drill includes police checkpoints in front of the United Nations, at 96th Street and Columbus Avenue, Broadway and Riverside Drive, Canal and Broadway, and Lafayette and Varick streets.

Also, there will be increased police activity at both terminals of the Staten Island Ferry.

More on Thursday’s drill from the Associated Press writer Tom Hays:

On a cold afternoon at the mouth of New York Harbor, a tiny yellow fishing boat bobs in the water as a flotilla of law enforcement vessels fitted with sophisticated radiation detection equipment closes in.

The boat has drawn suspicion by emitting gamma rays – a sign it may be carrying a dirty bomb, packed with radioactive material.

High-speed vessels from the New York Police Department and state Naval Militia halt the boat, tie it up and accomplish their mission of neutralizing an apparent terror threat.

The radiation was real, but the threat wasn’t: The scene Thursday was a drill designed to test an ambitious NYPD-led effort called Securing the Cities. The program aims to detect and intercept radiological devices before they can wreak havoc on Wall Street and other high-profile targets in Manhattan, the heart of the nation’s largest city.

The effort also has tested the limits of domestic counterterrorism logistics, costs and tactics. It relies on the manpower and expertise of more than 100 law enforcement and public safety agencies across New York, New Jersey and Connecticut, tens of millions of dollars in federal funding and a belief that plots already set in motion can be thwarted wherever necessary.

“That includes the waterways,” NYPD Commissioner Raymond Kelly said.

Security experts say such safety initiatives can’t just look good on paper. To work, first responders need to be drilled constantly using mock devices and various scenarios cooked up by their superiors.

READ MORE: WABC