Some years ago I responded to an accident scene on a mountain pass. The orginal report as received by our dispatch had been froma tourist in a bus, who had been sitting up high enough to see the subject vehicle. It had gone over the top of a guardrail, and was in such a position that most vehicles coming down the mountain couldn't see it, because the hillside dropped off so sharply as to hide it from view.
The person reporting the vehicle said it appeared someone had parked at the bottom of a steep incline, as was outside the vehicle, probably "taking pictures of flowers."
On arrival, the guardrail was damaged. We had no missing persons report and therefore no accounting for the number of people who might be involved. The vehicle was a four runner, the back end ripped off. It had rolled over the guardrail and down the incline. I found the first victim, tripped over him actually, face down just below the guardrail. He had been ejected and then crushed as the vehicle rolled over him. Beneath the vehicle we found the other victim, a young lady who was dead about three days. She had crawled free, propped a folded sweater beneath her head as a pillow, and there she lay, clutching her chest as though to stay warm. She appeared to have fallen asleep, but was dead.
We ran the plates, made some calls. Yes, these two were expected home, and now they were accounted for. I began a hasty expanding square search of the area, and soon found a third victim some distance downrange. He had been thrown well clear, and was laying face down, his arms by his sides, his neck broken from impact. Some distance past him was the fourth and final victim, a dog, in the same condition.
We had no idea of knowing how many victims there were, who might be alive where, or even how far to search. The last two victims were quite a distance from the final resting spot of the four runner.
What has that got to do with your question, you ask? Fast forward a few years to a crew that crashed New Mexico. One crewmember survived the crash, crawled clear, propped himself against a cactus. He died there. He was wearing a sage green nomex flight suit. He blended in, he was hard to find. That company began issuing indian orange flight suits immediately.
In an emergency, when responding to the scene, knowing how many people to look for is a very critical piece of informtion. It's not always available, but it's important to know in order to get adequate resources dispatched to the scene. It's important for searchers to know how many potential victims and the scope of what may be a mass casualty incident (MCI). It's important psychologically to prepare everyone for what's to come. It's important for accountability. I can tell you from personal experience that when searching for survivors, the knowlege hanging over you that you may be missing someone is a heavy weight. There's a lot to be said for knowing you've got everybody you came for.
Likewise, you're asked to identify the amount of fuel on board. This isn't just to state how far you can fly, but what kind of threat responders might face when they get there. The color of the aircraft is important...I've known of cases in which searchers found previously crashed aircraft and reduced the scope of the search, or saw the debris and didn't recognize it. Last year I overflew a crashed Cessna 210 three times while searching for it at low level in the snow in a King Air 200...I was looking for something else, and didn't have much information...I overflew it and didn't even see it. All the information that one can get is always helpful. Conversely, a few weeks later another crew went out in that same airplane and quickly located a helicopter that had crashed under similiar circumstances...they knew exactly what they were after, from the number of souls to the color and type, to the habits of the pilot. By knowing that last bit of information, they went where they thought he would have gone, and sure enough, there he was.
Knowing how many souls on board is a way of making sure nobody gets left behind.