Simulations and validations are necessary elements in the development of driverless cars, but they aren’t going to fully replace real world testing. Virtual testing will help engineers improve safety, but physical tests will be needed for system developers to understand how humans react to different driving conditions.

WCX panelists expressed a high level of confidence in simulations and validations, acknowledging that digital testing. But they noted that they’re no replacement for actual testing on public roadways.

“No matter how realistic simulations are, they’re not the same as testing in the real world,” said Jack Weast of Intel and Mobileye. “When you have pedestrians in simulations, how do you know that the pedestrians in these simulations react the same way real people do.”

Humans are largely predictable—someone walking down a sidewalk isn’t likely to suddenly leap onto a street, for example. But at the same time, people can be unpredictable. It will be important for humans and vehicles alike to understand how the other is likely to respond to changing conditions.

“It’s not just how vehicles interact with other vehicles, roads and rules,” said Ed Straub, director of SAE International’s Office of Automation. “They’ve got to respond to people who will vary region by region. There’s also an opportunity for determining how these vehicles communicate with us, they can give us clues about whether they’re automated or if a vehicle isn’t automated.”

Humans are only one of the uncertainties that arise as the industry moves towards automated driving and autonomy. Conventional vehicle systems have had a fairly limited number of potential failure points, but more sophisticated safety electronics have huge numbers of variants. Panelists discussed a few techniques, including the development of standards, that can make it easier to handle these variables.

“Traditional systems have a finite number of options, you can decide when a product is ready to go,” said Elektrobit’s Hurley Davis. “Now, there are limitless options. You don’t know how other people on roadways will react, you don’t know what vehicles will communicate with. We need standards.”