According to Uber, “However, our research shows that riders may not consistently report experiences that make them feel uncomfortable due in part to being distracted after the trip. When you are meeting friends for dinner, going right into a business meeting or coming home to family, reporting something like harsh braking or inappropriate remarks may not be top of mind.”
So if you use Uber often and come across a ride that you don’t enjoy, you’ll be able to send a report to Uber while the trip itself is happening. “Riders will see a “report safety incident” option in their Safety Toolkit (accessed by tapping the blue shield icon). Once they tap this feature, they will be able to report a non-emergency safety issue while still on the trip. Uber’s safety team will follow up after the trip.”
Note that this isn’t a feature meant to be used for emergencies, but rather just for general feedback about the trip and the driver. Uber recommends that users who need emergency help to contact 911.