Choosing denominators: per capita vs per distance; rankings that reverse
road safety
In 2025, Region A had 30 road deaths, a population of 300 000 and 3.6 billion vehicle-km travelled; Region B had 45 road deaths, a population of 600 000 and 4.5 billion vehicle-km travelled.
| Region | Road deaths (2025) | Population | Vehicle-km travelled |
|---|---|---|---|
| A | 30 | 300 000 | 3.6 billion |
| B | 45 | 600 000 | 4.5 billion |
Figure 1 shows the number of road deaths in each region every year from 2016 to 2025 (illustrative data). Population and vehicle-km travelled in each region changed very little over this period.
Time-series graph of the number of road deaths each year from 2016 to 2025 for Region A (about 22 to 38 per year) and Region B (about 36 to 52 per year), with both series fluctuating from year to year and no clear trend. Data are illustrative.Facts you may need
(a)
Calculate deaths per 100 000 people and per billion vehicle-km for each region.
(b)
Explain why the two measures rank the regions differently.
(c)
A minister says 'Region B's roads are the most dangerous.' Which measure supports this? Use Figure 1 to comment on how strong this evidence is, and state what else you would want to know.
(d)
Which measure would you use to decide where to spend road-safety money, and why?
