[eesmith]

The underlying paper comments the Czech Republic has high car ownership but relatively low use because of good public transport:

> The few exceptions where car modal share remains low and car ownership is relatively high, such as Switzerland, Japan, and the Czech Republic, have well-developed and efficient public transportation systems (e.g., public buses and subways) to satisfy their main mobility demand.

Thus, a ranking of "Vehicles per 1000 people" isn't necessarily indicative of vehicle use, and it's the latter which generates CO2 (for IC engines) and other pollutants, not mere ownership.

The paper calculates the effect of changing the modal share of bike use world-wide to match that of Denmark, and presents the first ever (to the authors' knowledge) substance for that calculation.