Another Tesla crash, another round of finger-pointing. This time, a Tesla owner in Los Angeles drove into the back of a parked fire truck on a freeway this past Monday while the car’s Autopilot semi-autonomous drive system was, according to the driver, engaged. Fortunately there were no injuries, but the National Transportation Safety Board indicated that it would send two investigators to look into the incident.

That last detail alone—that the NTSB would even show up for an otherwise straightforward rear-end collision on a highway—is actually the most significant part of this story, and it’s a telling indicator of what we’re up against as we march through the semi-autonomous phase of driving on our way to the Holy Grail of fully autonomous transport. This is new turf, and the NTSB needs as much data as it can get about what happens when drivers engage new technologies on public roads and things go awry.

This is the second time the NTSB has investigated a Tesla accident. The first one, in 2016, resulted in a fatality, andthe investigation found that the driver was over-reliant on the Autopilot system—using it in circumstances it wasn’t designed for—and also that the Tesla system allowed him to be that over-reliant, by not preventing its use on certain roadways and by not monitoring well enough the driver’s engagement. Monday’s crash likely won’t result in a full investigation, but it is an opportunity to collect that data on the safety of semi-autonomous systems.

As with the 2016 crash, the questions for the NTSB—again, keeping in mind that it’s not a full investigation—won’t be who was generally at fault in the crash, even though it might appear pretty obvious who was at fault. After all, Tesla’s Autopilot is a Level 2 autonomy system, which means it’s an advanced driver assistance device that can take control of the car under certain relatively constrained situations with the critical caveat that the driver is still in charge and responsible. So if that Tesla in California roared into the back of the fire truck at an estimated speed of 65 miles per hour...why didn’t he stop it?