From an operations standpoint, it makes sense with all of the power options and accessories available on vehicles, you may want power to move a seat, access a sunroof, move pedals, etc...
If you cut the wire, it is very difficult to hold the two ends together while someone else moves a power seat back!
Cutting battery cables does not affect the evidence in the so called "black box". It may cause the Collision Analyst to acquire the data in a different way from a different point in the vehicle (and be more work for them) but it does not alter, remove, or contaminate any data (evidence) that may be available post incident.
Removing/disconnecting a battery cable is perhaps a "better" option than cutting in most circumstances, but the purpose and reasoning for the fire service doing so, remains.
Above is what is commonly referred to as the vehicle "black box" and they are much less sophisticated and capable than those used in aircraft. The data is often accessed through the vehicle On Board Diagnostic (OBD) port. The EDR can also be connected to directly or removed from the vehicle and downloaded in the lab.www.cedtechnologies.com wrote:The Insurance Institute for Highway Safety describes an event data recorder (EDR) as a device that records certain information from a vehicle immediately before and/or during a crash Police, crash investigators, and others can download the data from the EDR's memory to help them better understand what happened to the vehicle and how the safety systems performed, and in some cases, help establish culpability.
Mechanical Forensics Engineering Services wrote:Up to now, manufacturers have each approached EDRs in their own way, but in August 2006, NHTSA issued a rule governing what data an EDR must record when a car has one. In January 2008, they issued their updated Final Rule which addressed some of the petitions they got after the first Rule was announced. It now applies to cars built after 01SEP2012. It mandates a list of things that an EDR must record if the car has an EDR which is intended to be downloaded after a crash. Think about that for a moment: if a car doesn't have an EDR intended to be downloaded after a crash, then the rule does not apply.
"Rusty Haight - Collision Safety Institute" wrote:There is no stand alone "EDR" in a car. An "EDR" is a function of another module (i.e.: rollover sensor or airbag control module). So, during a collision these modules do whatever it is they do and then, when their primary function is done they MAY, MIGHT, COULD record some crash related information as a function of the EDR capability of that module but that's going to happen long before the fire department shows up. If the module which has an EDR capability has done its job, it has long since recorded crash related data before the fire department cuts cables so their cutting those cables doesn't really impact the data but can make it "that much" harder for you to get data using the Bosch CDR System later.
Most of these "black box type things do hold some stored engery to keep working.
specific to your question I just did a hybrid/new vehicle technology 1 day deal and his answer to this was 'its a computer, it doesn't need power to remember, safety first'
If the vehicle is getting towed then disconnect the battery even if it is minor. Failing to do this could cause a fire due to a short in the system. And having put out a car fire in the middle of a towed car storage lot where cars are tightly packed together...i can tell you it is not fun.
but further, with all the myths about hybrid, HID lights, electricity in general I HIGHLY recommend bringing this program to your area. Invite all your neighboring department and send a few people from each department to bring the info back to their crews. We had 100+ people their from 15+ deparments i'd say.
are you afraid of hybrids and that scary orange wire...is it on and ready to drive away?? how about SRS systems and bleed down times?? you should be afraid of HID headlights, but with the right training it is just a car, metal and plastic like 100 years ago.
3rd Gen - I took the same course with MGS in Parksville. I am NOT an expert in vehicle extrication, nor do I pretend to be. However the information I learned in this class sure made me more confident if I have to deal with a hybrid vehicle involved in an MVA.
One of the "myths" that we discussed was air bags deploying while doing extrication. Only one documented case that the instructor knew of (Dayton, Ohio), and that was caused by a number of factors.
In order for an air bag to deploy, 3 things are required to make up an "event" - impact, deceleration, and speed. When all three are present and receive the right signals at the same time, then a "command to fire" will be initiated, and the air bag will deploy. Without all three, the air bags will not deploy. So all of the worry about air bag deployment after a crash is just a myth.
So - it is not possible to deploy air bags after the ignition is off, and the 12 volt battery has been disconnected. In answer to the original question, make the scene safe by disconnecting the battery - the information in the onboard computer will not be lost.
Stay safe !!
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