What can a “black box” tell us about a semi crash?

When we investigate a semi crash, one of the first things we do is preserve the black box data.

Preserving the “black box”

An electronic control unit (ECU) is the embedded system that controls one of more of the electrical systems or subsystems in a vehicle. This system – what we think of as a “black box” –  is present in both commercial semi-trucks and passenger vehicles built in the last couple of decades.

In most cases, that means preserving the Engine Control Module (ECM).

The ECM contains data about truck speed and braking. Looking at the truck speed and braking, both pre-collision and at the time of impact, can give us critical information about how and why a semi crash occurred.

Quick tip: You must send an official letter to the truck’s motor carrier requesting that

they do not destroy or alter evidence – including the ECM, or the truck itself.

It is incredibly important that the ECM data is preserved until it can be downloaded by an expert. This can only be done by taking the semi-truck out of service.

How we use semi crash data from the ECM

In a recent case where I was hired as a lawyer for people injured in a semi crash, I sent a preservation letter to the motor carrier and its insurance claims agent.

Then, we located and hired an appropriate expert witness, who came in and correctly downloaded the ECM data.

At the start of the case, it seemed clear that the trucker had been speeding, and failed to brake before hitting my client’s vehicle. The black data provided us with confirming evidence. Using this information, and other evidence, we were able to prove that the trucker was at-fault for the semi crash.

And if needed, we could have gone even farther with the data: pinpointing the semi-truck driver’s dangerous actions leading up to and at the point of impact.

In this case, it worked out. But we have seen it happen before: important evidence, including ECM data, is lost because there is no lawyer involved to force the trucking company to preserve it.

Attorney Kevin Coluccio, Coluccio Law.


CBS news_Lawsuit filed in truck bus crash_Coluccio Law


After a deadly bus-semi crash in New Mexico, a lawsuit was filed the very next day –  in order to preserve black box evidence.



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