NEW YORK (CBSNewYork) — The city knew that hundreds of bicyclists who shut down the Cross Bronx Expressway this past weekend, so why wasn’t the NYPD able to stop the bikers from entering the busiest highway in the country?

As CBS2’s Tony Aiello reported, hundreds of bike riders flooded the expressway this past Sunday, causing frustration delays. It was a dangerous stunt, though it seemed to delight the participants.

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“That’s no good. That’s looking for trouble,” said Hector Maccow of the South Bronx. “That’s looking for big trouble.”

The NYPD said it was monitoring social media, and knew hundreds of young bikers were planning a so-called “rideout.”

Police had followed their movements, ready to break things up if they got out of hand. But as riders approached the Webster Avenue entrance to the Cross Bronx, video shot by “Inside Edition” showed no police in place.

A high-ranking police official told CBS2’s Aiello that officers tried their best in a fluid situation – rushing units to the scene after a large group of bikers broke off from the rest and entered the highway.

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The source said even if officers shut down the ramp, bikers could easily access the highway by walking up grassy areas near other entrances.

At an event in Brooklyn, Aiello asked the mayor what his level of concern was about the “rideouts,” and whether police should have done more to keep them of the highway.

“Well, they’re not acceptable — let me make that very clear — anyone thinking of participating, not acceptable,” de Blasio said. “The NYPD will respond vigorously and there will be real consequences. A number of those people were arrested.”

A total of 16 people were busted for disorderly conduct. Police said they will study how the event unfolded to better prepare for the next one.

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CBS2’s Tuesday night report on the “rideout” generated hundreds of responses on Facebook. You can add your comment by going to our Facebook page.