Nix said there's essentially a spectrum on which these systems can be calibrated. Engineers can determine their sensitivity. That is, they can choose to reduce instances of false negatives — situations in which real obstacles might potentially be missed — by making the systems more responsive to perceived threats, which in turn makes them susceptible to false positives. Or vice versa.
Finding a balance depends on the philosophy of individual automakers and suppliers.
"Our theory was that we looked very closely to see how dangerous it would be to have a false positive," he said. "Hey, if we go into full emergency braking but only at less than 50 kilometers an hour, maybe that's an OK trade-off to brake for a ghost that isn't there. On the other hand, if you have a braking at 150 km, we might limit that braking because that risk equation is very different."
The Rogue evaluation isn't the industry's first brush with problems associated with false positives in automated emergency braking systems. It isn't even Nissan's first encounter with them.
Based on two complaints associated with inappropriate braking, NHTSA opened a preliminary evaluation in July 2012 into the Intelligent Brake Assist feature on the 2013 Infiniti JX35. In one complaint, a pregnant motorist driving with her 7-year-old son said her leased vehicle came to a "dead stop" on a bridge in Ocean Township, N.J.
After talking to a mechanic at her local dealership, she wrote to NHTSA, "I am told that this particular bridge is the only culprit in the entire country because it has too much metal."
In the ensuing federal evaluation, Nissan told federal safety officials that "unique road environment anomalies" may cause brake activations even when no threat is imminent. Investigators replicated the problem during their four-month probe but nonetheless concluded the braking interventions were "extremely brief and may interrupt travelling speeds, but do not stop the vehicle."
NHTSA said the inappropriate braking posed a "low risk to motor-vehicle safety." Investigators were satisfied a customer service campaign conducted by Nissan, which included a software reflash of the electronic control units that govern radar and Intelligent Brake Assist functions, would fix the problem.
It is unclear how the automated emergency brake system design evolved or changed from the 2013 Infiniti JX35 to the 2017 and 2018 Nissan Rogues. Documents from both the 2012 and ongoing 2019 federal evaluations show a matching 284E7 prefix on parts numbers associated with the driver-assist feature. It is not yet known how — or whether — the parts were modified in the interim. Parts numbers from the radar units change from 28437 to 28438 between the two investigations.
“Nissan is committed to the safety and security of our customers and their passengers," the automaker said in a statement. "Nissan has investigated this issue extensively and, in consultation with NHTSA, launched field actions notifying affected customers of a software update that improves MY17-18 Rogue AEB/FEB system performance.
"Customers are invited to bring their vehicle to an authorized Nissan dealership where the update will be applied at no cost to the customer. As always, Nissan will continue to work collaboratively with NHTSA on all matters of product safety.”
With regard to the reported problems with the Rogue, Nissan has sent seven communications, including a Technical Service Bulletin, to dealers with instructions on how to reflash the ECUs associated with the radar and driver-assist functions.
That guidance started coming out Sept. 6, 2016. The most recent came Aug. 17, 2018, informing dealers of a customer service campaign to update the software. But some wonder why the automaker hasn't issued a recall of the affected Rogues to ensure they receive the fix.
"At least here, we have an example of a fix that can be applied, hopefully," Levine said. "I think that NHTSA, if they are not writing a standard, they could at least set the bar that an AEB defect is a safety concern that requires a recall. At least you'd have a floor to work from that will hopefully enhance safety going forward."