NTSB: Uber’s Autonomous Car Had Disabled Emergency Braking System

Early results seem to indicate a conflict between Volvo’s ADAS system programming and Uber’s software stack for autonomous-vehicle operation.


By Murray Slovick, Contributing Editor

The National Transportation Safety Board (NTSB) released its preliminary report after investigating the crash of an Uber Technologies Inc. test vehicle. The vehicle was based on a modified 2017 Volvo XC90 and operating with a self-driving system in computer control mode. It struck a pedestrian who was walking her bike across the roadon Sunday, March 18, 2018, in Tempe, Ariz. The woman, Elaine Herzberg,died as a result of the accident.

While NTSB doesn’t yet indicate probable cause or fault, the report found that the Uber self-drive system detected the pedestrian six seconds before the crash. However, its software did not engage the car’s brakes to prevent the collision.

View of the self-driving system data playback at about 1.3 seconds before impact, when the system determined an emergency braking maneuver would be needed to mitigate a collision. Yellow bands are shown in meters ahead. Orange lines show the center of mapped travel lanes. The purple shaded area indicates the path the vehicle traveled, with the green line representing the center of that path. (Source: NTSB)

Here’s the exact language of the report:

According to data obtained from the self-driving system, the system first registered radar and LIDAR observations of the pedestrian about 6 seconds before impact, when the vehicle was traveling at 43 mph.


As the vehicle and pedestrian paths converged, the self-driving system software classified the pedestrian as an unknown object, as a vehicle, and then as a bicycle with varying expectations of future travel path.


At 1.3 seconds before impact, the self-driving system determined that an emergency braking maneuver was needed to mitigate a collision. According to Uber, emergency braking maneuvers are not enabled while the vehicle is under computer control, to reduce the potential for erratic vehicle behavior. The vehicle operator is relied on to intervene and take action. The system is not designed to alert the operator.

And this is how NTSB described the vehicle:

Uber had equipped the test vehicle with a developmental self-driving system. The system consisted of forward- and side-facing cameras, radars, LIDAR, navigation sensors, and a computing and data storage unit integrated into the vehicle. Uber had also equipped the vehicle with an aftermarket camera system that was mounted in the windshield and rear window and that provided additional front and rear videos, along with an inward-facing view of the vehicle operator. In total, 10 camera views were recorded over the course of the entire trip.


The self-driving system relies on an underlying map that establishes speed limits and permissible lanes of travel. The system has two distinct control modes: computer control and manual control. The operator can engage computer control by first enabling, then engaging the system in a sequence similar to activating cruise control. The operator can transition from computer control to manual control by providing input to the steering wheel, brake pedal, accelerator pedal, a disengage button, or a disable button.


The vehicle was factory equipped with several advanced driver assistance functions by Volvo Cars, the original manufacturer. The systems included a collision avoidance function with automatic emergency braking, known as City Safety, as well as functions for detecting driver alertness and road sign information. All these Volvo functions are disabled when the test vehicle is operated in computer control but are operational when the vehicle is operated in manual control.

While it’s still early in the investigation, it does seem that there was a conflict between the ADAS system programming in the Volvo and the software stack for autonomous-vehicle operation provided by Uber.

Interestingly, but debatable as to relevance, toxicology test results for the pedestrian were positive for methamphetamine and marijuana.

All aspects of the crash remain under investigation as the NTSB determines the probable cause, with the intent of issuing safety recommendations to prevent similar crashes.

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