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Pressure is mounting on Uber for it to let passengers who've allegedly been sexually assaulted by their drivers sue the company in public court.

Senator Richard Blumenthal, a Democrat from Connecticut, wrote a letter to Uber CEO Dara Khosrowshahi on Wednesday calling on him to release reported sexual assault survivors from their private arbitration agreements and let them sue the company in court. He said such agreements "silence" victims. (Update: Uber agreed on May 15 to drop arbitration agreements for victims of alleged sexual assault).

"I challenge you to finally demonstrate how seriously you take the issue of sexual harassment and assault," Blumenthal wrote. "Your company must lead by example and show that it values transparency and your users' safety more than your company's bottom line."

When people sign up to use the Uber app, they must click on and agree to the company's terms of service. Within those terms, it says riders agree that legal disputes with the company must take place in private arbitration -- not public court. It also means they cannot be part of a class action lawsuit with others who've gone through similar experiences.

San Francisco-based Uber, valued at around $72 billion, is one of the largest ride-hailing services on the planet, operating in nearly 75 countries. It gives millions of rides per day. But as Uber has grown, the company has come under fire for numerous allegations of drivers committing sexual assaults.

Uber has acknowledged the problem and says it's working to make its platform safer. It launched several new safety features last month, including an in-app emergency 911 button and tougher driver screenings that require annual background checks.

"Sexual assault has no place anywhere," an Uber spokeswoman said in an email. "We are committed to doing our part to end this violence."

Blumenthal's letter comes after a report from CNN found that at least 103 Uber drivers and 18 Lyft drivers have allegedly raped, forcibly touched or kidnapped passengers, among other crimes, over the last four years. To get that information, CNN combed police reports, federal court records and county court databases across the US. Both Uber and Lyft have declined to make public any data on such allegations.

The pressure on Uber to release alleged victims from private arbitration agreements started building last week when a group of 14 women wrote an open letter to Uber's board of directors. In their letter they said they were all sexually assaulted by Uber drivers in separate incidents. Nine of these women are suing Uber for the assaults and say the company misled them about the safety of its service.

"Forcing female riders, as a condition of using Uber's app, to pursue claims of sexual assault and rape in secret arbitration proceedings does not 'make streets safer.' In fact, it does the opposite," the women wrote in their letter. "Silencing our stories deprives customers and potential investors from the knowledge that our horrific experiences are part of a widespread problem at Uber."

If the case ends up in arbitration, the women named in the suit will still be free to speak to the public about the case. However, the day-to-day proceedings will be off limits.

Khosrowshahi has insinuated that he's open to dropping arbitration agreements in the case of passengers who've allegedly been sexually assaulted. In a tweet exchange with Susan Fowler, the former engineer who blew the whistle on Uber's workplace sexual harassment, Khosrowshahi said he'd explore her suggestion of doing away with the agreements.

Blumenthal, who is the lead sponsor of the Arbitration Fairness Act, said he supports the request made by the 14 women and urges Uber to "do the right thing," (which is one of the company's eight "cultural norms"). In addition to asking Uber to release victims of sexual assault from arbitration agreements, he said the company should also fully stop its practice of requiring such agreements in the first place.

"I call on you to immediately release survivors of sexual assault from Uber's arbitration provisions so that they may exercise their fundamental rights as Americans and pursue their complaints through the court system," Blumenthal wrote. "More broadly, I urge you to end your use of these dangerous agreements against your customers."

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