Calculating the risk numbers for passenger cars is a lot harder than the air. First, the data gathering is more challenging, thanks to the sheer number of vehicles on the road. The next thing is to estimate the number of car crashes a year. But, let’s make an attempt.
As per wiki, globally, about 1.4 billion motor vehicles are in use; a billion of them are cars. We don’t know how many journeys those make. Assuming an average of 100 days, you get 200 billion trips a year.
We use some shortcuts to estimate the number of crashes involving cars. India, which accounts for 11% of global death from road accidents, reports 150,000 fatalities from 450,000 incidents in a year. By extending the logic to the global scale, for the 1.3 million deaths every year, we estimate the incidents to be four million. We try yet another way of estimation. About 50 million injuries happen every year from vehicles and let’s assume half of them involve people travelling in the car (same ratio of reported death). The rest of them involves pedestrians and cyclists. Assuming an average of 3 people inside, we can estimate 25/3 = 8.3 million cars involved in incidents.
In the same way, 1.3 million deaths every year translates to 650,000 involving car travellers. That suggests a maximum of 650,000 fatal incidents and a minimum of 200,000 fatal incidents. Assume a mid-value of 400,000. Let’s compile all these (reported and assumed) into a table.
| Item | Data |
| # of car trips | 200 bln (estimated) |
| # road incidents | 4 – 8 mln (estimated) |
| # fatal incidents | 400,000 (estimated) |
| # deaths | 650,000 (estimated) |
| # passengers | 600 bln (estimated) |
| average trip length | 20 km (estimated) |
| passenger-km | 12000 bln-km (estimated) |
Calculated quantities
| Metric | Data |
| Incidents per trip | 20 – 40 (per million trips) |
| Fatal incidents per trip | 2 (per million trips) |
| Fatality per trip | 3.2 (per million trips) |
| Fatality per passenger-km | 54 (per billion-km) |
| Fatality per passenger | 0.81 (per million passengers) |
Now compare these with what we had estimated previously for the air.
Comparison – air travel
| Metric | Data |
| Incidents per trip | 3.13 (per million trips) |
| Fatal incidents per trip | 0.2 (per million trips) |
| Fatality per trip | 14.4 (per million trips) |
| Fatality per passenger-km | 0.06 (per billion-km) |
| Fatality per passenger | 0.13 (per million passengers) |
Looks like air travel is safer on all counts.
References
[1] http://www.rvs.uni-bielefeld.de/publications/Reports/probability.html
[2] https://economictimes.indiatimes.com/news/politics-and-nation/india-tops-the-world-with-11-of-global-death-in-road-accidents-world-bank-report/articleshow/80906857.cms
[3] https://en.wikipedia.org/wiki/Aviation_accidents_and_incidents
[4] https://www.who.int/news-room/fact-sheets/detail/road-traffic-injuries
[5] https://www.icao.int/annual-report-2019/Pages/the-world-of-air-transport-in-2019.aspx
[6] https://data.worldbank.org/indicator/IS.AIR.PSGR
[7] https://en.wikipedia.org/wiki/Aviation_safety
[8] https://accidentstats.airbus.com/statistics/fatal-accidents
[9] https://injuryfacts.nsc.org/home-and-community/safety-topics/deaths-by-transportation-mode/
[10] https://www.sciencedaily.com/releases/2020/01/200124124510.htm
