Uber has been testing a phone number that its passengers can dial in case of an emergency. According to Inc., Uber's emergency response line, called the Critical Safety Response Line, has been undergoing testing in 22 cities across the country since October. Quartz first found the phone number buried in Uber’s app in February. Uber hasn't notified riders or drivers about the number. Instead, it has placed the number in various locations within the app to test how easy it is to find and access. When a rider calls the number 800-353-8237 (800-353-UBER), they are transferred to one of two Uber Incident Response Teams, located in Chicago and Phoenix. But here's a crucial note: this isn't meant to replace 911. Rather, the phone number could be used to help passengers retrieve phones, keys, medication, and other items accidentally left in a vehicle after a trip. Calls placed to the center could also deal with concerns about a driver. The discovery comes as more concerns have surfaced regarding Uber’s safety protocols and just one month after Uber driver Jason Dalton was charged with six counts of murder in February.