NEW YORK -- Hundreds of new protective barriers will be permanently installed in Times Square and other locations around New York in an effort to block vehicles from hitting pedestrians after deadly attacks last year on crowds. The city is spending $50 million on protective measures including the installation of 1,500 metal barriers, or bollards, in key locations around the city, Mayor Bill de Blasio said Tuesday.

Known around the world for the New Year's Eve ball drop, Times Square is crowded most days with tourists, costumed characters, sightseeing bus hawkers and office workers.

In May, a man said by police to be high on drugs drove through crowds for more than three blocks, killing an 18-year-old tourist from Michigan. The vehicle was eventually stopped by one of the squat metal barriers. Temporary concrete blocks were put up along the Seventh Avenue sidewalk while city officials weighed a long-term solution and considered banning vehicle traffic from the area all together.

Then, on Halloween, a man who claimed to be inspired by ISIS drove down a busy bicycle path near the World Trade Center, authorities said. He killed eight people before he wrecked his rented truck and was shot and wounded by police. Barriers have also been placed there to keep cars out of the bike path.

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"In 2017, New Yorkers witnessed the horrible capacity of people willing to do us harm, whether it was in our subways, on our bike paths or in Times Square," de Blasio, a Democrat, said. "We know we have to do even more to keep people safe and that's why we conducted a review on how best to secure our streets and public spaces, and we formulated a plan of action."

The rollout will begin in March. Meanwhile, the temporary blocks already set up will remain in place. "People have to be able to get around but they have to be safe at the same time," de Blasio said.

City officials didn't specify what other locations will be fortified, beyond the bike path and Times Square, but said there would be barriers set up in all five boroughs.

Officials in Europe have also been grappling with the threat of vehicle attacks in recent years after terror suspects used similar tactics in France, Germany and Britain.

Last August, former FBI assistant director Ron Hosko said it's "almost impossible" to defend sidewalks from vehicles "in an urban setting."

"I think there is a way with those high-concentration areas, and we see it outside of sports stadiums, we see it in other places, we see it right behind us, where it's a safer pedestrian area and tourist area and citizen area behind us than it is on the street," Hosko told CBS News transportation correspondent Kris Van Cleave.

His comments came after Charlottesville police said James Alex Fields Jr. drove his car into a crowd, killing a 32-year-old woman and injuring at least 19 others in a matter of seconds.

"There is no cost-effective way to secure every sidewalk in a major city -- there is none," Hosko said. "We can harden targets that are high concentration areas, but we're always going to be vulnerable."