Cover photo

How road deaths are counted and why the math matters

Every time you get into a car, there is a non-zero chance that you might get injured, or worse, die. The probability of this happening depends largely on where you're driving and, of course, how much you drive. However, there are a few different ways to measure this statistical risk. A recent Bloomberg article by David Zipper highlights one ongoing debate.

The three most common methods are:

  • Road deaths per capita

  • Road deaths per registered vehicle

  • Road deaths per distance traveled

In my opinion, options 1 and 3 seem the most relevant. Option 1 is useful because it measures a citizen's overall risk and allows driving risk to be easily compared to other causes of death (which tend to be measured on a per capita basis). The limitation is that it is harder to compare a country where everybody drives to a country where few people drive.

That's where option 3 comes in. In theory, it provides the best indicator of road risk by accounting for distance traveled, which is the primary argument for why it's commonly used in the US where the car is king. But it does "dilute" the fatality count the more people drive, and it hides overall car dependency. In his article, Zipper likens this approach to measuring cancer deaths per cigarette smoked.

In any event, here is how both methods appear in the International Transport Forum's 2025 Annual Road Safety Report (which is cited in the article):

post image
post image

On a per vehicle-kilometre basis, the data appears much more gradual. But on a per capita basis, the countries with the highest road fatalities appear much more as outliers. Here, you can more easily see that, broadly speaking, a person in Colombia is nearly ten times more likely to die in a road-related incident than a person in Norway (pretty much the gold standard when it comes to road safety).

Perhaps the answer is to just look at both figures to make sure you're not lying to yourself.


Cover photo by Tom Barrett on Unsplash

Charts from Road Safety Annual Report 2025