The NTSB's report contains a few surprises, including how and where Tesla's captured data is stored, routed and saved inside a vehicle.
The National Transportation Safety Board (NTSB) last week released, after more than a year of suspense, a 500-page document or “docket,” about a fatal highway crash involving a Tesla S and a tractor-semitrailer truck.
For an automotive industry now fixated on the development of self-driving cars — among which the Tesla S is one of the grand experiments — the NTSB probe is a treasure trove of data. However, it falls short of determining who, or what, is to blame for the death of the driver.
The NTSB docket includes reports on highway design, vehicle performance, human performance, and motor carrier factors. The crash reconstruction report, included in the docket, describes the crash sequence, along with interview transcripts and summaries, photographs, and other investigative details.
The NTSB emphasized that the docket contains “only factual information collected by NTSB investigators” and it “does not provide analysis.” It said no conclusions about how or why the crash occurred should be drawn from the docket. The NTSB is planning to release its own analysis, findings, recommendations, and a judgment about probable cause “at a later date.”
Using system performance data downloaded from the passenger car, the report states that its speed just prior to impact with the trailer was 74 mph. The data also revealed that the driver was operating the car using automated vehicle control systems, a Traffic-Aware Cruise Control (TACC) and the Autosteer lane-keeping system.
Driver Assistance System
Among the documents released last week, the one entitled “Driver Assistance System” poses particular interest for EE Times readers.
The report delves into details of how Tesla’s driver assistance system — consisting of a Bosch radar system, Mobileye image capture & processing system, an ultrasonic sensor system and gateway electronic control unit — works. It literally reads like a teardown of the Model S driver-assistance system.
It also contains a few surprises, including how and where Tesla’s captured data is stored, routed and saved inside a vehicle, and how it’s sent to Tesla’s server using a virtual private network connection established via Wi-Fi, or using the vehicle’s 3G cellular data capability.
The report says that Tesla S stores non-geo-located data in-vehicle in non-volatile memory using a removable SD card installed within the Gateway ECU.
Really, an SD card? What role does the SD card play?
No Event Data Recorder?
After reading the report, Mike Demler, a senior analyst at The Linley Group, told EE Times, “I find the description of some of Tesla’s control and data-recording systems to be interesting.” In particular, he said, “The statement in the report that says, ‘This SD card is large enough to typically maintain a complete record of all stored data for the lifetime of the vehicle’ is interesting.” He asked: “How could they determine how much data will be generated over the lifetime of the vehicle?”
Unfortunately, the NTSB report doesn’t answer such questions.
But one thing is clear. The NTSB apparently sees this “removable” SD card as a proxy for an event data recorder (EDR). Because current NTSB specs do not require an EDR (it's completely voluntary), the NTSB appears to conclude that Tesla did enough.
Danny Kim, director and partner of Vision Systems Intelligence (VSI), told EE Times, “The Tesla Model S involved in this crash did not, nor was it required to by regulation, contain an event data recorder.” Even had it included an EDR, he noted that “The current EDR, outlined by the regulation, is outdated and it does not reflect what autonomous vehicles can do.”
Kim said, however, that sooner or later there will probably be a new regulation including an EDR mandate, per NHTSA’s recommendations last fall.
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