The ride sharing service Uber has been quietly testing an emergency hotline for passengers.

Uber has faced safety concerns lately, after an Uber driver was charged with killing six individuals and injured two more during a shooting rampage in Kalamazoo, Mich. this February. The driver picked up Uber passengers for rides in between the shootings.

The hotline’s number is 800-353-8237 (UBER). Customers who call that number, which Business Insider calls Uber’s “secret” emergency number, will speak first with a customer service representative, and then to 911 if the problem is severe enough.

The hotline has been in its testing stages since October, when it was introduced to the Uber system in 22 cities. The hotline is simply listed under the Help button on the Uber app, though customers who know the number may call, whether or not they are in one of the cities with a hotline pilot program. Kalamazoo is not one of the cities that features the hotline. Uber’s Incident Response Teams are based in two cities, Phoenix and Chicago. 

“We are always looking for ways to improve communication with riders and drivers,” the company said in a statement. “In select U.S. cities, we have a pilot program where riders and drivers can call an Uber support representative directly for assistance with an urgent situation after a trip.”

Uber says that it does not want its secret number to replace 911 in case of emergency.

“In the United States, 911 is the panic button and it’s the panic button that we want people to use,” said Uber’s security chief Joe Sullivan, after the Kalamazoo shootings. “It’s the panic button that law enforcement wants people to use. And we don’t want to try and replace that.”

So why does Uber need a hotline? According to the company, the hotline is not intended to respond to Kalamazoo type emergencies, but rather to less-pressing problems or complaints, such as belongings left in the backseat of an Uber vehicle.

After the Kalamazoo shooter, Jason Brian Dalton, began to act erratically during an Uber call, a passenger reported him to 911 and filed a complaint with the company. Mr. Dalton had passed Uber’s main security feature, a background check.

“We are horrified and heartbroken at the senseless violence in Kalamazoo,” Uber’s security chief Joe Sullivan told CNN after the incident, “We have reached out to the police to help with their investigation in any way that we can.”

Uber has also faced hundreds of reports of sexual assault and rape, according to BuzzFeed News.

The problem goes both ways, however, with Uber drivers also reporting cases of verbal and physical assault by passengers, according to Wired. Because ride sharing service drivers are considered independent contractors and not employees, companies like Uber and Lyft are not able to give them safety training.

Altogether, it has been a difficult year for Uber in the security department.

In early February, Uber agreed to pay $28.5 million in a class action lawsuit regarding the terminology of its “safe ride fee,” which customers say misrepresented Uber’s security procedures. Although Uber previously called its background checks “industry leading,” it was revealed that drivers were merely put through a routine background check by a service.