Analyze This
When is the cause of a crash NOT the cause of the crash?
When it's being analyzed in FMCSA's Crash Causation Study

By Jami Jones
senior editor

When someone in the trucking industry - or the motoring public, for that matter - talks about the "cause" of a wreck, the word requires little explanation.

That's clearly not the case with the Federal Motor Carrier Safety Administration's newly released Crash Causation Study. In fact, in the first pages of the study, the authors ponder the definition of "cause."

The Owner-Operator Independent Drivers Association Foundation took a hard look at an interim report and FMCSA's report to Congress on the study, and saw problems with it right away.

When all was said and done, the study was conducted in a way that relies on a statistical definition of "causation," which defines "cause" in terms of relative risk.

The study, rather than reporting who was at fault and why, is actually a collision-avoidance or crash-prevention study focused on pre-collision events rather than the consequences.

"Its purpose is to increase knowledge of the factors associated with large truck crashes," the executive summary concluded. "With greater understanding of the events and conditions that lead to crashes, the objective is to develop strategies to decrease their frequency."

That purpose and the intention of the study have escaped many who began citing statistics - erroneously - from the study almost immediately following its release.

That's not too hard to understand when you look at an example cited throughout the methodology summary:

"A truck turns across the path of an oncoming car at an intersection. The critical event is the truck's turn across the path of the other vehicle . The truck had the turn arrow, observed the oncoming vehicle, and assumed that the oncoming vehicle would stop, which proved to be incorrect. (Right-of-way, which is captured separately, does not necessarily determine the critical event, because the collision may still be avoidable.) The critical reason is 'false assumption of other road user's actions.' "

Huh? The car ran the red light, so it is the cause of the crash. Why is the trucker being hit with statistical labels of "critical event" and "critical reason?"

What the study does is look at car-truck crashes from a statistical analysis point of view.

For the purpose of data collection for the study, the "critical event" is the starting point because the researchers defined it as the vehicle movement that made the collision inevitable.

So, back to the example, the trucker who had the turn arrow was assigned the "critical event," because it was the vehicle movement of the truck that made the collision inevitable. Given that action, the collision could not be avoided by normal driving skills or vehicle-handling properties.

The immediate reason for the critical event is coded as the "critical reason." It can include driver decisions and conditions, vehicle failures and environmental conditions.

That means the trucker was also assigned a "critical reason" because of the assumption that the car would stop at the red light.

The trucker's "critical reason" is lumped in with the final statistic that reports that truck driver decision plays a role in an estimated 88 percent of all truck crashes, when broken down by critical reason.  

However, driver decision was cited as the critical reason in only 38 percent of the crashes.

That said, one can also note that truck drivers were coded less frequently for both driving performance errors and non-performance problems - for example: asleep, sick or incapacitated - than passenger vehicle drivers.

The study goes on to break down the percentage of "associated factors" present in the crashes studied - something like a driver talking to a passenger at the time of the critical reason.

So you have all these critical events, critical reasons and associated reasons that are coded to vehicles and drivers. But just what those vehicles are may surprise you as well.

The broadest definition of "large truck" was used in the study. There were 976 crashes studied - 60 percent involved large articulated trucks and 40 percent involved straights weighing more than 10,000 pounds. But that statistic isn't being picked up on either in the mainstream.

The statistical validity of the number of wrecks is being challenged by the likes of transportation researchers. There were slightly less than 1,000 wrecks studied. More than 140,000 happen each year involving big trucks. Yet researchers took the percentages from the study and assumed they can be used to break down the reasons contributing to the other 139,000 wrecks.

Do those stats from the study tell the tale for the industry as a whole?

With more questions arising out of the Crash Causation Study than answers, chances are, when all is said and done, you will see stories written with statistics cited that are either horribly misleading or dead wrong.

For example, this is FMCSA's exact headline on the press release announcing the report to Congress: "New study concludes driver behavior causes most truck crashes."

Did anyone at FMCSA actually read the study? The authors were very clear that it is not a report on cause. Remember, it's a look at collision avoidance or crash-prevention focused on pre-collision events.

Many stories in the media are telling readers that driver behavior caused 88 percent of truck crashes.  

Wrong again.

What the study says is that action or inaction by the driver of either the truck or other vehicle was the critical reason for 88 percent of the crashes.

Remember the example, when a critical reason was assigned to the fact that the trucker assumed the other driver would stop at a red light?

Makes you wonder just how misleading this 88 percent could be to people who think it's talking about the cause of wrecks or legal fault, doesn't it?

All of this is not to say that the study isn't worth the paper it's written on. It's just unfortunate that it is not a study of causes, but is - and will continue to be - sourced and reported that way.

It does confirm what many of us on the roads and in the industry have known all along - that driver behavior must be targeted in wreck-reduction efforts, in cars and trucks alike.