https://www.newscientist.com/article/2170049-uber-self-driving-car-saw-woman-but-didnt-brake-before-crash/

In a preliminary report on the crash, the National Transportation Safety Board (NTSB) said emergency braking manoeuvres are not enabled while Uber’s cars are under computer control “to reduce the potential for erratic vehicle behaviour”.

Instead, Uber relies on a human backup driver to intervene but the system is not designed to alert the driver.