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Nine women are suing Uber. They say they were sexually assaulted by the ride-hailing company's drivers.

Originally, two women filed the lawsuit in November. Since then, seven more plaintiffs have signed on. Uber has said that all court proceedings must take place in private arbitration, rather than be open to the public, because of agreements the women clicked on when they signed up to use Uber's app.

On Thursday, these nine women, plus another five who allege sexual assault at the hands of Uber drivers, sent a plea to the company's board of directors asking it to release them from the private arbitration agreement. (Update: Uber agreed on May 15 to drop arbitration agreements for victims of alleged sexual assault).

"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 14 women wrote in an open letter to the board, which was obtained by CNET. "Silencing our stories deprives customers and potential investors from the knowledge that our horrific experiences are part of a widespread problem at Uber."

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. But with its growth, the company has come under fire for numerous allegations of drivers committing sexual assaults.

A handful of states, including California, Colorado, Massachusetts and Texas, have previously launched investigations into Uber, claiming it routinely fails to adequately screen drivers and has hired drivers with criminal histories. Reports of women allegedly being sexually assaulted by Uber drivers make news headlines several times a month.

Uber has acknowledged the problem and says it's working hard to make its platform safer. It launched several new safety features earlier this month, including an in-app emergency 911 button and tougher driver screenings that require annual background checks. It also stopped giving drivers a log of passengers' pick-up and drop-off addresses.

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

'Safe rides'

Uber uses a third-party screening company called Checkr to conduct its background checks. Checkr does a seven-year criminal history check at a series of national, state and local databases, along with looking at the National Sex Offender Public Website and other databases. However, some security experts say these checks aren't as thorough as state and FBI fingerprint background checks -- something Uber has long refused to do.

In their open letter, the 14 women say that by pushing to hold the lawsuit in private arbitration, Uber is hiding the potential danger of using its app. They say that when they created their Uber accounts, they believed they were going to get the "safe ride" that the company promotes.

Several of the women detail their personal experiences with Uber drivers in the letter, which range from allegations of rape to being locked in the car and forcibly groped to the driver masturbating during the ride. The alleged assaults took place across the US, including in Pennsylvania, Florida, California, Michigan, New York, New Jersey and Iowa.

"As Uber devotes its resources towards an IPO, it must disclose to potential investors the magnitude of the problem it has regarding Uber drivers that sexually assault or rape their female riders," Jeanne M. Christensen, a partner at law firm Wigdor LLP who's representing the women, said in an email. "The critical first step in such transparency is to let our clients litigate their claims through the court system and not bully them into the secret halls of confidential arbitration."

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.

Uber CEO Dara Khosrowshahi has insinuated that he's open to holding the lawsuit in open court. In a tweet exchange with Susan Fowler, the former engineer who blew the whistle on Uber's workplace sexual harassment, Khosrowshahi said he'll explore her suggestion of doing away with the private arbitration agreement -- when it comes to people who were allegedly sexually assaulted.

"I'm trying and our company is bought in," Khosrowshahi tweeted to Fowler last month. "I will take a look at your suggestion -- I will take it seriously but we have to take all of our constituents into consideration."

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