Among the many criticisms Uber faces is a persistent allegation that the company does far too little to protect the safety of passengers or respond to their claims. Why, critics demand to know, isn't there some kind of panic button or 911 line riders can use to get help in an emergency or report a driver who's behaving strangely, like the one who recently went on to kill six people in a shooting spree in Kalamazoo?

As a matter of fact, there is. Uber just doesn't want it too widely known.

After four months of keeping it under wraps, Uber confirmed the existence of an emergency response number to Inc. on Wednesday, saying it was part of a pilot program that's been running since October in 22 cities.

Quartz first reported on the existence of the line in February, in a story about how a panic button could improve safety on the platform. But Uber told Inc. on Tuesday that it had no hotline for drivers. On Wednesday a representative amended that response, saying the reason for the seeming discrepancy is that the line -- called a "Critical Safety Response Line" -- is not technically a hotline.

Hotline or critical response line, Uber isn't telling drivers or riders about it either way. The company says it has abstained from announcing the number's existence -- even in the 22 cities where it is being piloted on the app -- because part of the test is for "discoverability." Basically, the company wants to see if people can find the number on their own. The pilot also includes a/b testing, which a representative said could include changing where on the app people find the number, though she said she believes the number has been findable in the same part of the app since it was released.

The number connects drivers and riders with two "centers of excellence" in Chicago and Phoenix, where dozens of representatives on Incident Response Teams are available to respond at all hours. Representatives are trained to call emergency services if a caller is in a position of immediate danger, according to Uber.

The line is not meant to replace a call to 911 according to Uber. An example a representative provided of use for the line was someone leaving insulin in an Uber car. In such a case, emailing customer support would provide too slow of a response, and but calling 911 might be extreme.

"We are always looking for ways to improve communication with riders and drivers. 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," reads a statement provided by Uber.

Uber said it is not releasing the locations where the number is being piloted on the app at this time. Anyone who has the number, published in the story by Quartz, can call it regardless of where they are calling from.

Confirmation of the line comes following a story by Buzzfeed about thousands of customer support tickets that contain phrases like "rape" and "sexual assault," raising questions about whether safety issues were more prevalent on the platform than previously imagined. Lyft has a line that is publicly known.

Uber's decision not to tell drivers and riders about the line speaks to a lack of transparency, says a former Uber driver who pointed out the existence of the line to Inc. in response to reading that an Uber spokesperson said the platform did not have a hotline.