Nearly 2,000 New York Police Department officers “equipped with an additional level of training, heavy vests and long guns” were on guard around the city on Tuesday, said a spokesman for the NYPD.
Police departments in Boston, Baltimore and Chicago said they were taking additional precautions as well, particularly around outdoor holiday events.
Since a truck attack in July killed 86 people in Nice, France, many cities stepped up their use of “blocking vehicles” to stop drivers who might be using trucks as weapons, said Edward Davis, a former Boston police commissioner who oversaw the department during the 2013 Boston marathon bombings.
(At least 9 people were killed when a truck plowed into the crowd at a popular Christmas market in Berlin, Germany. Witnesses describe it as a deliberate attack. CBS News correspondent Charlie D’Agata has the latest. Courtesy of CBS News and YouTube)
The NYPD recently used the vehicles as barriers during the Macy’s Thanksgiving Day Parade.
Blocking vehicles are typically dump trucks filled with sand and deployed in strategic locations to stop vehicles from barreling into an area, said Mr. Davis. “We’re going to see more of that as this becomes a more frequent tactic,” he said of attacks involving trucks.
“Clearly this is the newest threat we’re facing,” he said.
Heavy traffic in big cities like New York makes truck attacks difficult, according to the NYPD.
“It’s actually hard to get up to speed to run anybody over,” said John Miller, the department’s deputy commissioner for intelligence and counterterrorism, on MSNBC on Tuesday. “On the other hand, we look at this on a layered approach.”
(Police in some U.S. cities are in heightened states of alert after Monday’s truck attack at a Berlin Christmas market. Heavily armed units patrolled similar markets Tuesday in New York and Chicago, while in Atlanta, police say “they are monitoring the situation.” Courtesy of CBS Evening News and YouTube)
Mr. Miller said after previous truck attacks, police visited 140 truck companies to make them aware of signs of suspicious behavior.
Although a commercial driver’s license is required to rent most vehicles bigger than a light box truck, most companies do some level of additional screening when people come in to rent or lease trucks, said Jake Jacoby, president and CEO of the Truck Renting and Leasing Association, an industry group that includes U-Haul, Penske Truck Leasing Co. and Ryder System Inc.
Penske says it requires two forms of valid identification, and each renter’s name is run through a watch list of known criminals. The company says it also keeps in close contact with federal law-enforcement agencies, and sends out regular bulletins advising rental agents about potential threats.
Rental-company employees are generally instructed to contact a supervisor if something doesn’t seem right, including if a person doesn’t respond readily when asked what the vehicle will be used for. “If they can’t tell you right away that is a red flag,” Mr. Jacoby said.
After the Berlin attack, which killed at least 12 people, the Boston Police Department stationed additional officers at an outdoor holiday market in City Hall Plaza, a spokesman said.
In Chicago, police said they were monitoring the situation in Germany closely and staying in regular contact with federal and international law-enforcement agencies. The department said it is beefing up patrols in a downtown plaza where a popular German-style event called Christkindlmarket is held.
Police in Baltimore said they, too, were following events in Berlin.
“Our antennas are certainly raised, and we’ve put our ears to the ground to find out if this is something that could visit Baltimore,” said department spokesman T.J. Smith.
Mr. Davis, the former Boston police commissioner, said he hasn’t heard of municipalities discussing checkpoints to watch for suspicious trucks coming into cities, but that “in my mind that would be a logical next move.”
Charissa Isidro thought of the truck attacks in Berlin and Nice when she went to the Union Square holiday market in New York on Tuesday and saw counterterrorism officers there.
“It’s just sad because these places are supposed to be places where you’re enjoying the holiday season,” said Ms. Isidro, a 21-year-old student at New York University.
After the truck attack in Berlin, Ms. Isidro said she realized she was unprepared for such an act.
“If there was a giant vehicle, coming straight towards me what would I do?” she said. “It’s weird we have to think of that now. … I feel like now this is part of surviving in the city.”
Law-enforcement officials say lone-wolf attacks involving vehicles have become more common since Sept. 11, 2001.
In 2006, Mohammed Taheri-azar drove a rented sport-utility vehicle through a courtyard area on the campus of the University of North Carolina at Chapel Hill, hitting nine pedestrians. He pleaded guilty to nine counts of attempted murder and was sentenced to up to 33 years in prison, according to news reports at the time.
Daniel Linskey, who spent nearly three decades with the Boston Police Department, said that after 9/11, trucks were often banned on highways near special events, including the 2004 Democratic National Convention in Boston.
Concrete bollards and temporary metal barriers are also used to minimize the damage from truck attacks.
Attacks involving vehicles are much more difficult to prevent than attacks involving firearms, Mr. Linskey said, because firearms are less accessible and require more training to use. “Anyone can drive a car 80 miles an hour into a crowd of people,” he said.
Another concern is that such attacks require little preparation, said Eugene O’Donnell, a professor of law and police studies at John Jay College of Criminal Justice.
“Someone can decide a short time before carrying out an attack, on impulse, to do this. It does not require acquiring firearms,” Mr. O’Donnell said. “An actor can go from thought to action in a very abbreviated period. And Manhattan at holiday time offers infinite opportunities to create carnage.”
A 2010 article in “Inspire,” the English language magazine used by al Qaeda in the Arabian Peninsula, urged would-be recruits to use pickup trucks as a way to carry out a terrorist attack.
“We don’t really know what to look for in terms of pre-attack flags and indicators,” said Brig Barker, a retired Federal Bureau of Investigation special agent who focused on counterterrorism. “It’s definitely not a science.”
—Jennifer Levitz and Scott Calvert contributed to this article.