Tuesday’s deadly terror attack in which a man is alleged to have driven a truck into a crowd of pedestrians and bicyclists on a New York City bike path has revived concerns that more such attacks could happen in U.S. cities.

Some cities are beefing up security, and advocates are renewing calls for more investment in barriers to prevent vehicles from entering spaces with heavy pedestrian traffic.

Police say eight people were killed and a dozen injured when 29-year-old Sayfullo Saipov mowed them down on a Manhattan bike path Tuesday afternoon. Authorities say Saipov acted alone and was influenced by the Islamic State.

In the wake of Tuesday’s attack, New York tightened security at airports, the subway system, and Penn Station, officials said Wednesday.  The city is also boosting surveillance, adding car blockage, snipers, and heavy weapons teams for Sunday’s New York City Marathon, which is expected to draw more than 50,000 runners and 2.5 million spectators along the route.

The attack was the latest in which a vehicle used as a weapon has terrorized a city, though most have occurred in Europe. It was also the deadliest such attack on U.S. soil.

In other cities around the world where such attacks have happened, including Barcelona, London and Berlin, barriers have been erected for added safety. Some have installed posts known as bollards, oversized flower pots, sculptures and cement barriers along busy pedestrian thoroughfares. Some say it’s time for the U.S. to do the same.

“We have had plenty of warnings about these things happening,” said Rob Reitier, a pedestrian safety expert.  “This is another call for actions on safety and security.”

Even before the attack Tuesday in Manhattan, some U.S. cities were installing barriers to protect pedestrians after similar attacks in Europe.  Those stepped up efforts included installing bollards and security barriers, as well as increased police presence at big events.

In Washington, D.C., the Metropolitan Police Department said it is “vigilant to any potential threats” in the capital area and is working with other local and federal agencies to ensure the safety of residents and visitors.

Authorities across the country are asking residents to remain vigilant and report suspicious activity.

“We are working tirelessly to prevent anything like this from getting repeated,” New York Police Commissioner James O’Neil said at a morning news conference.

New York officials said they would look into the lack of bollards as part of the investigation. Experts say bollards could have prevented the rented truck from entering the bike path where users encounter maintenance, garbage trucks, and police vehicles on a daily basis.

Investments in tools such as protective barriers will help improve pedestrian safety whether they are pushed for counter-terrorism or not, experts and advocates say. Permanent bollards and bigger curbs are some options that can protect the places that have become target for terrorists.

“There’s no way that you will ever make a city perfectly safe from a terrorist attack,” said Tamara Evans, an advocate with the Washington Area Bicyclist Association. “But there are ways that we can be protecting infrastructure so that it is harder to get a vehicle onto it.”

In Las Vegas, 700 bollards are being installed along the Las Vegas Strip this year in an attempt to protect bystanders from deliberate acts to use vehicles as weapons. Though there’s no specific threat, authorities said recent terrorist propaganda featuring snapshots of Las Vegas Boulevard can’t be overlooked.

In New York, officials have been calling for the installation of more bollards, citing the ones that stopped the speeding sedan in a May incident that left one person dead and 22 injured.

The Los Angeles City Council voted this summer to direct the police department and other agencies to issue a report on mitigation methods for vehicle attacks.

In addition to metal bollards and concrete barriers that provide greater separation between cyclists and drivers, some advocates and experts say U.S. cities should start looking at creating more pedestrian-only streets.

“If a vehicle can get on a trail at some point, a vehicle will get on a trail,” Evans of the WABA said. “How do we make it harder? How do we make it impossible? There are design elements that can do that and cities should be prioritizing those. We can’t prevent everything, but we can make it a lot harder.”