The causes of the fatal Tesla Model S crash, that occurred in May last year, while the vehicle’s Autopilot function was engaged, included an over-reliance on vehicle automation technologies and a lack of safeguards, the USA’s National Transportation Safety Board (NTSB) has found. The report has led to the USDOT and NHTSA releasing new safety recommendations for automated vehicles.
The driver of a 2015 Tesla Model S was killed when the vehicle collided with a 2014 Freightliner Cascadia semi-tractor-trailer on US Highway 27A on May 7, 2016. The Tesla’s Traffic-Aware Cruise Control and Autosteer lane-keeping assistance features were being used by the driver at the time of the crash.
NTSB’s Tesla investigation
The NTSB accident investigators found that the Tesla was traveling at 74mph (119km/h) just prior to impact. The posted speed limit was 65mph (104km/h). As a result of its investigation, the NTSB also determined the operational design of the Tesla’s vehicle automation system permitted the car driver’s overreliance on the driver-assistance technology, noting its design allowed prolonged disengagement from the driving task, and enabled the driver to use it in ways inconsistent with manufacturer guidance and warnings.
Findings in the NTSB’s report include:
The Tesla’s automated vehicle control system was not designed to, and could not, identify the truck crossing the Tesla’s path or recognize the impending crash. Therefore, the system did not slow the car, the forward collision warning system did not provide an alert, and the automatic emergency braking did not activate;
The Tesla driver’s pattern of use of the Autopilot system indicated an overreliance on the automation and a lack of understanding of the system limitations;
If automated vehicle control systems do not automatically restrict their own operation to conditions for which they were designed and are appropriate, the risk of driver misuse remains;
The way in which the Tesla Autopilot system monitored and responded to the driver’s interaction with the steering wheel was not an effective method of ensuring driver engagement;
Tesla made design changes to its Autopilot system following the crash. The change reduced the period of time before the Autopilot system issues a warning/alert when the driver’s hands are off the steering wheel. The change also added a preferred road constraint to the alert timing sequence;
Fatigue, highway design and mechanical system failures were not factors in the crash. There was no evidence indicating the truck driver was distracted by cell phone use. While evidence revealed the Tesla driver was not attentive to the driving task, investigators could not determine from available evidence the reason for their inattention;
Although the results of post-crash drug testing established that the truck driver had used marijuana before the crash, his level of impairment, if any, at the time of the crash could not be determined from the available evidence.
As a result of its investigation, the NTSB issued seven new safety recommendations and reiterated two previously issued safety recommendations:
To the US Department of Transportation (USDOT) –
1. Define the data parameters needed to understand the automated vehicle control systems involved in a crash. The parameters must reflect the vehicle’s control status and the frequency and duration of control actions to adequately characterize driver and vehicle performance before and during a crash.
To the National Highway Traffic Safety Administration (NHTSA) –
2. Develop a method to verify that manufacturers of vehicles equipped with Level 2 vehicle automation systems incorporate system safeguards that limit the use of automated vehicle control systems to those conditions for which they were designed.
3. Use the data parameters defined by the USDOT in response to safety recommendation as a benchmark for new vehicles equipped with automated vehicle control systems so that they capture data that reflects the vehicle’s control status and the frequency and duration of control actions needed to adequately characterize driver and vehicle performance before and during a crash; the captured data should be readily available to, at a minimum, NTSB investigators and NHTSA regulators.
4. Define a standard format for reporting automated vehicle control systems data, and require manufacturers of vehicles equipped with automated vehicle control systems to report incidents, crashes and vehicle miles operated with such systems enabled.
To manufacturers of vehicles equipped with Level 2 vehicle automation systems (Audi of America, BMW of North America, Infiniti USA, Mercedes-Benz USA, Tesla Inc., and Volvo Car USA)
5. Incorporate system safeguards that limit the use of automated vehicle control systems to those conditions for which they were designed.
6. Develop applications to more effectively sense the driver’s level of engagement and alert the driver when engagement is lacking while automated vehicle control systems are in use.
To the Alliance of Automobile Manufacturers and to global auto makers
7. Notify your members of the importance of incorporating system safeguards that limit the use of automated vehicle control systems to those conditions for which they were designed.
As a result of its investigation, the NTSB reiterates the following safety recommendations to the NHTSA
Develop minimum performance standards for connected vehicle technology for all highway vehicles.
Once minimum performance standards for connected vehicle technology are developed, require this technology to be installed on all newly manufactured highway vehicles.
“While automation in highway transportation has the potential to save tens of thousands of lives, until that potential is fully realized, people still need to safely drive their vehicles,” said NTSB chairman, Robert L Sumwalt III.
“Smart people around the world are hard at work to automate driving, but systems available to consumers today, like Tesla’s Autopilot system, are designed to assist drivers with specific tasks in limited environments. These systems require the driver to pay attention all the time and to be able to take over immediately when something goes wrong.
“System safeguards, that should have prevented the Tesla’s driver from using the car’s automation system on certain roadways, were lacking and the combined effects of human error and the lack of sufficient system safeguards resulted in a fatal collision that should not have happened.”
The NTSB is an independent federal agency charged with determining the probable cause of transportation accidents and promoting transportation safety.
There are still no universal rules or regulations in which autonomous vehicles can operate, and the potential legal issues surrounding autonomous vehicles are undefined. Autonomous Vehicle Safety Regulation World Congress 2017, which takes place at the Suburban Collection Showplace in Novi, Michigan, on October 23-24, will address this and present an environment in which to discuss and explore how to create a regulatory framework to enable further public testing of autonomous and driverless vehicles.
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