Vehicle black box downloads are now available in most vehicles on the road. Most people are surprised to learn that they tucked away a crash data recorder out of sight in their car or truck. They can obtain the data in a matter of minutes. This information contains the speed of their vehicle up to 5 seconds prior to a collision.
Even those who are aware of the existence of black boxes don't realize that they have equipped some vehicles with the units for almost thirty years, starting with the 1974 Cadillac. Vehicle black box downloads are common practice after an accident.
The application of air bags caused the existence of these devices in order to store the proper criteria and control the timing of airbag deployment. An assembly of sensors and associated microelectronics had to be mounted on the vehicle to determine when all the conditions were correct, as in a frontal crash, to blow the bag out.
Almost in step with increasing use of airbags was the more elaborate use of microprocessor controllers for engine management, emission reduction functions and antilock brakes.
These, in turn, required sensors to measure such parameters as engine speed, wheel speed and throttle position. These and other device additions converged on enough vehicle models by the early 1990s to provide the foundation for recording various data items in a rolling memory.
The recorded data in memory is continually revised and updated as old data is discarded, so that a five-second snapshot is always available and is frozen in memory when a collision occurs.
The Event Data Recorder (EDR), as the rolling memory is called, has its functionality actually incorporated into the air bag controller, which is the Sensing and Diagnostic Module (SDM) on GM vehicles or Restraint Control Module (RCM) on Ford products.
That's the unit which, in some manner, has always been needed to determine when the bag should deploy in an accident situation. In its present day form, a typical module looks like the one shown in the photograph.
It's important to know that every car or truck which has at least one air bag also has an event data recorder of some type. As with most electronic modules, the EDR is often called a "black box."
Since the accelerometers, the devices which sense the amount and direction of vehicle motion are packaged together with all the electronics, the location of the module in the vehicle must be near its center of gravity. That requirement normally leads to placement under either the left or right front seat, or inside the center console.
Vehicle black box downloads often require the technician to cut through the carpet under the car seat. The unit can be removed or multi-pin connector can be attached to the module. They attached the connector to an external computer.
The process of collecting data from vehicle black box downloads is sometimes called "harvesting." The data can be harvested by attaching pins to the black box or by removing the EDR.
Regardless of the method chosen to physically connect to the EDR module, the read-out hardware and software remain the same as shown. The data conversion, interpretation and display software is loaded into a PC laptop.
The basic information of interest for accident reconstruction is:
Download a Sample Black Box Download Report from a 2007 Dodge Charger SRT8 here.
There are many highly visible precedents which clearly show that the courts readily accept EDR data.
Even as far back as 1992, in a case involving Jerome Brown of the Philadelphia Eagles, the court denied a claim by his family that his car had hit a pothole and the airbag deployed prematurely causing him to lose control of the car and his life. Reconstructionists, using the EDR, proved that Brown was speeding, lost control and struck a tree before the airbag deployment.
More recently, in February 2003, the court accepted EDR evidence that a woman in Ipswich, Massachusetts was speeding when her car slid off an icy road, struck a tree and killed her passenger.
Then, in May 2003, the EDR was used to prove that a Pembroke, Florida man, was traveling at nearly 120 mph when his car hit and killed two young girls.
The future of vehicle black box downloads is clearly headed toward greater reliance on this data.
The accident scene investigation
Atlanta Engineering Services, Inc. offers scene mapping... read more here
Why you need an expert witness
Multiple surfaces calculator to determine the stopping distance when there is more to consider.
Vehicle speed calculator
Accidents involving motorcycles
How a vehicle inspection analysis can help you after an accident
Reconstructing accidents involving Non-Commercial trucks
It just may be those roadway ruts that caused you to hydroplane, find out more here
More 3D accident reconstruction videos can be found here
See actual photos of traffic accidents here