For the second time in three months, Mayor Bill de Blasio has suggested that there should be a law forcing cyclists of all ages to wear helmets.

In September, de Blasio told CBS2's Marcia Kramer that mandatory helmet laws—which have been shown to depress overall rates of cycling in other major cities—were "something we are studying right now."

At a press conference on Wednesday, Kramer again asked the mayor about mandatory helmet laws, citing a National Transportation Safety Board meeting on Tuesday in which the board recommended that all 50 states pass mandatory helmet laws.

"The NTSB just said that the only way to reduce the increase in bicycle fatalities is to require helmets," Kramer said. (In fact, the NTSB said that promoting better infrastructure, road diets, and decreasing vehicular speed would also lead to decreases in crashes and fatalities.)

"Marcia, I think it's time for us to really focus on this in New York City," de Blasio said. "I hear the voices that say, 'Hey, we don't want to discourage people from riding bikes, it's good for the environment, fighting climate change, it’s good for reducing congestion.' I hear that. I really do. But we have to have an honest conversation about the value of bike helmets."

The mayor added, "I don't have the magic formula yet, but I think the NTSB is pointing us in the right direction."

Kramer, who once suggested that the existence of the Second Avenue bike lane would promote domestic terrorism, pressed the mayor further, specifically asking if he wanted to see a law passed.

"Marcia, I think I said very clearly, I want to make sure we balance those two pieces. I think they really both matter. Clearly, I think it's time to consider legislation or regulation that would improve the situation," the mayor replied.

The mayor's position contradicts that of his Department of Transportation Commissioner, Polly Trottenberg, who is a former undersecretary for policy at the federal Department of Transportation.

"DOT supports people wearing helmets. We don't support making it mandatory," Trottenberg said a few weeks ago.

A DOT spokesperson told Gothamist on Wednesday, "We look forward to reviewing the final report’s full text, which is still under revision and will be released later this month." (Governor Andrew Cuomo has indicated that he won't sign a bill legalizing e-bikes unless e-bike riders are required to wear helmets.)

The NTSB has made around 14,000 safety recommendations in its history, with around 82 percent of them being closed or addressed to their satisfaction, according to the board. The majority of their work concerns the aviation industry, since they are charged with investigating every aviation crash in the country, around 1,300 each year. The NTSB hasn't had a hearing on cycling safety in 47 years.

Most #bicycle fatalities involve a motorist overtaking a bicyclist. Focusing safety countermeasures on that type of crash scenario can seriously reduce injuries and fatalities overall. https://t.co/m6rspe9L5j pic.twitter.com/T4eqI9pCO9 — NTSB (@NTSB) November 5, 2019

NTSB member Jennifer Homedy, who proposed the mandatory helmet law recommendation, told Gothamist that the other recommendations the board made yesterday were getting "lost" in the helmet law controversy, including research on collision avoidance technology, and creating a "coalition of stakeholders to develop a comprehensive national strategy to increase bicycle helmet use among bicyclists of all ages that would include, at a minimum, a model all-ages bicycle helmet law."

"We are focused on a comprehensive approach to safety, and helmets are just to focus on the head injury aspect of it," Homedy said. "It's preventing the crash in the first place. It's roadway design, it's separated bike lanes, and it's implementation of technology in vehicles, and reducing speeds."

Research strongly suggests that helmet laws depress cycling rates, which in turn negatively affects the "safety in numbers" phenomenon crucial to safe cycling. Did the NTSB just declare that the safety benefits of wearing a helmet outweigh the decrease in crashes found in cities with higher rates of cycling?

"No, first of all, I do agree that more cyclists actually improve safety. Where I don't agree is the premise that requiring helmets would reduce cycling," Homedy said, pointing to the roughly 60 jurisdictions in the U.S. where there are mandatory helmet laws for all cyclists.

One of those jurisdictions used to be Dallas, Texas, until they repealed the law in 2014, after they found it discouraged cycling and that enforcement of the law disproportionately fell on communities of color, a problem that persists in New York City today without any mandatory helmet law.

"Personally of course, that is a concern, I would not want to see that," Homedy said, but suggested that racially biased enforcement of helmet laws was not the purview of the NTSB.

"Our mission is safety. Our focus is preventing crashes and preventing injuries and saving lives," Homedy said. "That's where we come at these issues. It was unpopular at the time, when we recommended seatbelts, when we recommended motorcycle helmets, when we recommended airbags," Homedy noted. "None of those were well-received."

Homedy, who described herself as a "road cyclist and a triathlete," urged cyclists concerned about the helmet law to join the "coalition of stakeholders" that the NTSB recommended. (You can watch the full NTSB meeting here.)

Jon Orcutt, a former DOT official who is now the director of communications at Bike New York, said he didn't expect the NTSB's recommendation to spur mandatory helmet laws in New York City. The recommendations, are after all, just that. Many states don't require adults to wear motorcycle helmets. In 2013, the board recommended that states lower the BAC intoxication level to 0.05 from 0.08, but so far only Utah has done so.

"I think the mayor's Transportation Department—they're very articulate on this topic," Orcutt said, noting that a mandatory helmet law for all cyclists would "kill one of the best biking trends we've seen under de Blasio."

"We're talking about doubling the size of Citi Bike, which is already huge. A helmet law kills that," Orcutt said. "There's no way Citi Bike is going to supply helmets to all 100,000 daily riders."

Orcutt added, "I think the whole federal transportation safety establishment is very fragmented and I think broken. There's nobody in the federal government who's gonna say, look, if you plan a city or town more efficiently, people are going to walk and bike, not drive. That's not even a conversation happening at a federal level.

"They're decades behind in a real conversation about bike safety or sustainable transportation or people-focused transportation."