Charles C. Roberts, Jr., Ph.D., P.E.

The evolution in computerized automotive technology has resulted in data being stored in various memory devices (black boxes) throughout the vehicle (1, 2, 3). Only recently, some of this data has become accessible to the automobile accident investigator and is proving to be as valuable in accident reconstruction as other information such as tire mark distances and points of impact. During an accident, whether the airbag deploys or not, information such as vehicle speed, throttle position, brake application, engine RPM, seat belt usage and airbag status is recorded in nonvolatile memory. Figure 1 shows the sensing diagnostic module (black box) found in most late model vehicles with airbags.

Figure 1

The data in the black box on about 30 percent of the vehicles on the road can be downloaded onto a laptop and used as evidence in subrogation related actions. As an example, take the “stuck throttle” claim depicted in Figure 2. The insured claimed that the accelerator stuck and that he had difficulty controlling the vehicle, causing an accident. Inspection of the vehicle showed that the accelerator pedal may have engaged the carpet, causing it to stay about 50% depressed as shown in Figure 2. The pedal can catch in the plastic wear guard, leading one to conclude that either a defective design of the carpet or defective installation exists.

Figure 2

Figure 3

Figure 3 is the download from the black box in graphical form. The horizontal axis shows seconds before impact. The vertical axis graphs vehicle speed (MPH), engine speed (RPM/100), percent throttle opening and brake switch status (brake on or off). At 5 seconds before impact, the brake switch is 100 = ON, indicating the brake pedal has been pressed. The throttle position is 62% open. The vehicle speed is 53 MPH and the engine RPM is about 2800. At one second before impact, the brake switch is 100 = ON, indicating the brake pedal continues to be pressed. The throttle position is 62% open. The vehicle speed is 32 MPH and the engine RPM is about 2700. Since the brake is pressed, the driver’s foot is not on the accelerator, and the engine speed should quickly drop to idle or about 800 RPM. In this case, the throttle stays about 62% open, which tends to substantiate the claim that the accelerator pedal stuck. Figure 4 shows additional data from the download, which indicates that the driver was not wearing his seat belt.

Figure 4

Black box data is a form of evidence that could be influential in subrogation and at trial. The consensus among legal scholars is that black box data is the property of the vehicle owner. As always, permission from the insured or a court order is necessary to download the data. It should be noted that some data is time dependent and after a certain number of ignition cycles is erased.

Black box data is expected to revolutionize automobile accident reconstruction, rendering speed and velocity change calculations obsolete is certain cases. Although not all black box data is readily available, more vehicles will be equipped with accessible memory as time goes on. Currently, software is available to access the black box data on about 30% of the vehicles on the road. Availability of favorable black box data at trial can form a credible basis for legal arguments as to why a particular party should prevail.

1. “Claims Issues and the Supplemental Individual Restrain System,” Claims Magazine, December 2003, pp 30-32.
2. “Inside the Mind of a New Car,” Claims Magazine, June 1994, pp 36-44.
3. “Computer Fault Codes Interest Investigators,” Claims Magazine, March 1989, pp 91-92.