Buried inside Uber’s inaugural safety report this week that detailed thousands of sexual assaults and more than 100 deaths was another staggering revelation: Hundreds of rape allegations have gone undisclosed to law enforcement.

Uber said in its 84-page transparency report, released Thursday, that law enforcement was involved in only 37 percent of the 464 reports of rape during Uber’s U.S. rides in 2017 and 2018. That suggests police weren’t aware of nearly 300 rape allegations, potential felonies. Uber didn’t disclose the involvement of law enforcement in the 6,000 reports of sexual assault. That means police are potentially unaware of thousands more cases of sexual assaults.

Uber chief executive Dara Khosrowshahi said the ride-hailing company doesn’t automatically share reports of sexual assault with law enforcement because advocacy groups recommend leaving that decision up to the victim. “Our first order is not reporting to the police,” Khosrowshahi said in an interview with The Washington Post on Friday. “Our first order is to help the survivor.”

The finding that Uber knows vastly more than police about the scale of rape and sexual assault during its rides is raising alarms among law enforcement, regulators and victims advocates who say the company keeps valuable information to itself — and struggles to take responsibility for what happens on its platform.

“These numbers represent a staggering systemic failure,” said Sen. Richard Blumenthal (D-Conn.), a frequent critic of ride-hailing services who accuses them of dodging responsibility for safety concerns. He has called on Uber to do more to make the problem apparent to the proper authorities. “In that time of vulnerability when a victim comes forward, the difference may be the level of encouragement that Uber gives that could lead them to law enforcement.”

Former San Francisco district Attorney george Gascón, who sued Uber over its safety claims and failure to institute fingerprint-based background checks, said the company’s revelation raises serious issues with the platform and its aggressive expansion.

“I think it’s extremely troubling that we’re finding out now that only a third of [offenses] have been reported because what we know also is that people who engage in sexual assault and receive no consequences tend to reoffend,” said Gascón, who is running for Los Angeles County district attorney. “I would never advocate for forcing a survivor to report to law enforcement because that could often be traumatizing the survivor again. But I don’t believe that looking the other way and just simply shelving the thing is the right approach.”

Of the 2.3 billion U.S. Uber trips in 2017 and 2018, such reports occurred on a fraction of a percent of total rides.

Investigations by The Post have shown how Uber and its rival Lyft have shied away from taking responsibility for safety issues. The Post in September found that workers in Uber’s internal Special Investigations Unit are forbidden from passing to law enforcement credible felony claims and from sharing data with Lyft or other companies that could keep them from hiring dangerous people. Uber said its investigators are trained to direct those who report sexual offenses to its preferred outside victim advocacy group for further counsel.

For months, victims advocates’ calls for Lyft to put safety features in place went unheeded. Sexual harassment victims said Lyft fell far short of their expectations in addressing their complaints, giving them boilerplate responses and in some cases casting blame on their actions leading up to the incidents.

Victims rights groups and other experts said the thousands of reports of sexual assault could represent just a fraction of the incidents during ride-hailing trips.

In general, many sexual assaults go unreported: A 2013 survey from the Bureau of Justice Statistics, a division of the Justice Department, said 34.8 percent of rapes were reported to law enforcement, close to the same proportion as with Uber. And many other instances of sexual assault occur during rides set up by Lyft. That means there are potentially hundreds more rape incidents that have never reached law enforcement. Lyft hasn’t yet published its inaugural safety report.

Lyft spokeswoman Alexandra LaManna said Lyft was in discussions with Uber as recently as Thursday about how to establish an information-sharing process.

Khosrowshahi said the company’s recent efforts to crack down by adding new safety features have contributed to a decrease in reported incidents year-over-year. But he said the numbers were still too high.

“I’m not satisfied with that. It’s half of a too-big number,” said Khosrowshahi, who mandated in May 2018 that Uber produce the safety report. “The goal for us is zero. We are incredibly demanding of ourselves, and this is a start for us.”

In the report, Uber disclosed that in 2018, there were 235 reports of rape and 3,000 reports of sexual assault. In contrast to the 37 percent of rapes in which police were involved, Uber estimated that only 10 percent of episodes of “non-consensual touching of a sexual body part” were reported to authorities, according to a sample it conducted of 100 cases. The company said it was intentionally broad with its definitions of what constituted certain offenses in an effort to make the report as comprehensive as possible. It collected data from its own reporting apparatuses, police departments and any other sources of information that could provide a comprehensive view of known incidents on the app.

Uber, in the report, called on other industries to produce their own safety reports. Chief Legal Officer Tony West said in his executive summary that “it’s our intention to make an impact well beyond our own company, encouraging others to be more transparent with their data and to share best practices that can make everyone safer.”

New York City’s Taxi and Limousine Commission says it encourages taxi and ride-hailing passengers to report allegations of crimes, such as sexual harassment or assault by a driver, directly to the New York Police Department. Unlike in other cities, New York Uber drivers have to be licensed by the TLC, just like taxi drivers, through a process that includes an extensive background check, drug testing, fingerprinting and a 24-hour training course. The commission says it received 28 complaints of sexual harassment and six alleging sexual contact in 2018.

Police involvement is not a magic solution to the problem of sexual violence, said Cindy Southworth, executive vice president at the National Network to End Domestic Violence, who also serves on Uber’s safety advisory board. “People think police is the answer, and it’s often not what survivors want. What survivors want is they want other people to be safe, they want to prevent someone else from being harmed. But if the survivor wants to go to law enforcement, the beauty is there is a fair amount of digital evidence that Uber has.”

Mike Bomberger, an attorney with Estey & Bomberger, which has filed lawsuits against Lyft over 34 cases of alleged rape of sexual assault, said that by concealing the scope of the problem from police, Uber had neglected its duty to the public trust.

“Nothing that they have done is defensible regarding not reporting these incidents to police,” he said. “Look at the consequences of not reporting: What’s the message you send to your drivers if you know a crime’s been committed in the car, you’re aware of it and it’s not been reported to police? Number two: You know that a particular driver has committed a crime, is a sexual predator, and now you’re going to let that sexual predator back into the public to do whatever sexual predators do. You look at the pros and cons, and there’s no way you can defend not reporting that to police.”

He said at the very least, the company needs to encourage victims to come forward to prevent bad actors from reoffending.

Allison Tielking, a Stanford University student who has been an outspoken advocate on the issue after alleging repeated instances of sexual harassment on Lyft, said she spoke with Uber executives this fall about how to address the problem. She advocated a system in which Uber informs victims of the potential benefits of notifying police. “You should make them aware of what happens, what the broader impact is — it’s not just you having to deal with this reporting to police on your own; this could potentially save the lives of many other potential survivors because this person now is getting kicked off of every app.”

Uber said it is in discussions with law enforcement and advocates to determine the best approach to encourage reporting of incidents by those who wish to go to the police, as well as how to connect them to authorities. The company said it directs police to a law enforcement portal where they can easily find detailed information on trips if victims do come forward, in an effort to speed up law enforcement requests. Meanwhile, the company directs victims to a Rape, Abuse & Incest National Network hotline to lay out their options and can help them advise law enforcement. It’s working with that group to establish a “dedicated survivor hotline that will provide confidential crisis support and specialized services to survivors” by 2020.

Lyft said it has a 24/7 law enforcement team and a policy to respond to all valid police requests. The company’s privacy policy, however, requires a subpoena or other “valid legal process” in order to give user information, in an effort to protect potential victims’ identities and to allow the user “to be the core decision-maker when it comes to deciding whether and how to report an incident,” according to LaManna.

Uber and Lyft both said Thursday that they were considering means for sharing data with one another regarding banned drivers, known as deactivations. The companies currently have a policy against handing over that information, even to background-check firms, as it is considered proprietary. That means that drivers who are restricted from Uber or Lyft for violations like assaults on passengers or poor driving can, with impunity, simply register as a driver for the other company.

The risk inherent in not passing along information about bad drivers came into stark relief over the summer when Chicago officials found that an Uber driver who fatally kicked a taxi driver in a 2018 dispute had been deactivated for punching a passenger weeks earlier while driving for Lyft, which had failed to report it. Had the company disclosed it to the city, as required within 48 hours, Uber may not have allowed the driver, who has since fled to China, to work for it, officials contend. Lyft has admitted the error and will pay a $10,000 fine.

“We’re committed to finding a way to share the names of drivers who have been banned from our platform for the most serious safety incidents with our ridesharing peers,” Uber said in its report. Lyft said it is working toward sharing “information about drivers who don’t pass our initial or continuous background checks or are deactivated from our platform.”

Some of the reporting issues stem from systemic issues at Uber’s Special Investigations Unit, a call center in Phoenix that is charged with handling the most sensitive reports from passengers and drivers. The Post revealed in September that workers in that unit were charged with serving the company’s interest first, seeking to avoid liability for safety issues, guided by a policy that prohibited reporting to police.

Because of the frequent occurrence of the offenses, Gascón said, Uber has an obligation to offer therapy, psychological services and medical services, and to undertake extensive efforts to address the problems.

“We’re now placing Uber at a position where they’re placing the public at large at risk,” Gascón said. “Look, Uber disrupted the public transportation system and in some areas for good, other areas the jury is still out — but given that you created that disruption for all the other systems, were not necessarily prepared to address all the byproducts of that disruption, then you have an obligation to start also being part of a solution.”

Heather Kelly contributed to this report.