Calgarians spend a significant portion of their lives whizzing around at a hundred kilometres an hour, encased by a thousand kilograms of steel.

We call it commuting.

For roughly half the year, we do this on roads covered in snow and ice, surrounded by fellow commuters careening about. We travel in packs, sometimes close enough to reach out and touch the vehicle beside us.

And, every so often, things go wrong. Really wrong.

Last Friday was one of those days. On an icy bridge deck shrouded by fog, a chain-reaction started. Driver after driver crashed into a massive wreckage that eventually grew to claim 50 vehicles. Nine people were sent to hospital, once they could be extracted from the twisted mass of metal. And that was no small task.

Untangling the wreckage took hours. Sorting out exactly what happened will take weeks. And assigning blame — a fundamental premise in our province's insurance system — could take months, even years.

With such a complicated crash, where do you even begin?

There's a natural tendency to want to point a finger at a single person. Chatter on social media is, of course, already laying blame. But police say don't jump to conclusions. And the insurance industry says there's usually plenty of fault to go around in crashes like this.

And in Alberta, that matters.

Why blame matters

Things would be different if this crash happened in a province with "no-fault" auto insurance.

Under that type of system, each person's insurer would pay them for the damages to their vehicle — and, potentially, medical and other costs, too — regardless of who caused the crash. That's not to say there are no consequences for the at-fault drivers. They would likely be slapped with higher insurance premiums in the future.

Alberta, by contrast, has what's known as a "tort" system.

A tort is legal principle that refers to wrongful action that causes harm to someone else. And sorting out who committed a tort in a crash is essential, because that person's insurer is on the hook for the damages.

In practice, though, assigning blame can be complicated — and contentious. Disputes often arise in a two-vehicle crash, so you can imagine the challenges that come with a 50-car pileup.

"That's where things get very complex," said Rob de Pruis with the Insurance Bureau of Canada.

"In many cases, there would be shared responsibility over multiple different people."

Just imagine, hypothetically, there's a crash. The person at the front of a chain-reaction collision suffers a neck injury. How much of that injury is due to the first car that rear-ended her vehicle? How much of it is due to the next car that struck the car behind her, driving it further forward? And the next car in the wreck? And the next one?

With something like the Stoney Trail crash, you also have impacts on both sides of some vehicles. It becomes a three-dimensional puzzle to sort out.

Enter, the police.

The limits of dashcams and skid marks

You likely have an image in your head of traffic officers on the scene of a crash, tracing tire tracks and calculating skid distances.

Calgary police say that indeed happens after simple collisions. But in a massive pileup, it all blends into an indecipherable mess.

Physical evidence is marked on a road after a two-vehicle crash in Calgary. When dozens of vehicles are involved, however, police say it's nearly impossible to gather this kind of evidence. (CBC)

"Once you get a multitude of vehicles like that involved in a collision, utilizing the physical evidence left on the roadway is going to be almost impossible," said acting Staff Sgt. Chris Gauvin.

"In a collision like that, you'll typically have to rely on the witness evidence."

Witnesses, however, often offer incomplete — sometimes conflicting — versions of events. Memories get especially hazy in traumatic situations. That's why police try to interview witnesses as quickly as possible after a collision, before recollections fade.

Of course, when liability is involved, some people will have an interest in minimizing their own role in a collision.

That's where dashboard-mounted cameras come in, right?

Actually, not so much.

Gauvin said they're still not as common as many people believe. While dashcam video is helpful, he said police can't yet rely on it to piece together chains of events.

In more serious crashes, he said police will try to obtain other forms of objective information, such as data from vehicles' airbag modules and onboard sensors.

It can take weeks or even months for police to complete a report on a complex collision.

In the meantime, insurance adjusters are conducting their own investigations.

Months to investigate, years to litigate

While insurance companies often make use of police reports to help determine who's at fault, they don't necessarily need to wait for those to be completed.

They, too, will interview witnesses and gather evidence — photographs, video and data — as they work to sort out liability.

When dozens of vehicles are involved in a crash, a multitude of insurers will all be doing their own investigations and, usually, communicating with each other at the same time. Typically, de Pruis said, there will be "a lot of phone calls" going back and forth as adjusters negotiate with one another, and their clients, to try to settle who pays for what.

Sometimes, though, talks break down. And that's when the lawyers get involved.

"I'll have people call me anywhere from a few days after a collision all the way to almost two years after a collision," said Ryan O'Fee, a Calgary-based lawyer who specializes in motor-vehicle crashes.

Like police, lawyers don't rely heavily on dashboard cameras. O'Fee estimates only five per cent of the cases he sees involve dashcam video, and while the quality of recordings is improving, it's not always great.

"They sometimes are still blurry," he said. "It's hard to make out licence plates."

A dashboard camera captured this high-quality footage of a collision on Deerfoot Trail in 2016, but police and lawyers say dashcams are still not common enough to be a reliable source of collision reconstruction. (Nick Xu/YouTube/Screenshot)

More and more, he said, it's the on-board vehicle data that makes it into evidence. Modern vehicles are equipped with what O'Fee likens to the "black box" on aircraft.

The more sophisticated modules will tell you exactly when a driver accelerated or braked — even when they changed lanes. Lawyers will send all that data to accident-reconstruction engineers who analyze the information and build a picture of the most-likely scenario that led to a collision.

It's rare for cases to actually make it to court, however.

O'Fee said people usually end up opting for private settlements or mediation to resolve their disputes. If clients insist on going to court, it's a long process — especially in Alberta, where there is a persistent shortage of judges.

If you tried to book a two-week trial today, O'Fee said, you'd be looking at a start date sometime in 2020, maybe 2021. And that's assuming you already have all the evidence prepared.

Take your foot off the gas

Given how long it takes for the law to sort out these types of crashes, police warn against jumping to conclusions based on snippets of information gleaned from the news or social media.

​"I would say that we'd have be very cautious when we start listening to what people are saying online," Gauvin said. "Because, with a collision like this, there could be so many different things that caused it."

Generally, in a chain-reaction crash, there will be multiple rear-end collisions — and, therefore, multiple people at fault. Drivers who run into the back of another car are generally considered to be liable for the collision, O'Fee said, although there can be mitigating factors. Every situation is slightly different, and blame can be divvied up in any number of ways.

Still, if there's one piece of advice from driving instructors, it's to keep your distance from other vehicles. Following too closely is the No. 1 cause of collisions in Alberta, according to Ron Wilson, manager of driver education with AMA.

At 50 km/h or less, he advises at least a three-second following distance. When travelling at highway speeds in poor conditions, he recommends upping that to four to six seconds.

"That way, if someone ahead of you happens to stop or brake quickly, you're going to have no problem doing that yourself," he said.

It's a simple thing that could prevent you from ending up in a complicated crash.

Calgary: The Road Ahead is CBC Calgary's special focus on our city as we build the city we want — the city we need. It's the place for possibilities. A marketplace of ideas. So. Have an idea? Email us at: calgarytheroadahead@cbc.ca