The verkeerscentrum maps the traffic density (the traffic 'volume', or number of cars) in Flanders, Belgium for the calendar year 2018 (mean, weekdays). The density ranges between 0-20k, 20k-50k, 50k-80k, 80k-100k, and 100k-140k. Highest density is identified at the ring of Antwerp and the ring of Brussels.
The 'verkeerscentrum' is managed by the Flemish government.
You can access the website/create the map overview via this link: http://indicatoren.verkeerscentrum.be/vc.indicators.web.gui/indicator/index.
In Ireland in 2017, the total road traffic volume was 2,684,730 according to state official data on data.gov.ie.
477 private cars per 1000 inhabitants
Source: Sveriges officiella statistik: Trafikanalys (Swedish official statistics: Transport Analysis)
15.490,503 cars registered in 2015
source: Kenya Road Transport: No of Motor Vehicles
Number of vehicles registered in Norway in total exist through SSB (https://www.ssb.no/en/transport-og-reiseliv/statistikker/bilreg/aar/2017-03-28), but finer data in terms of vehicle per citizen or which regions these numbers are higher than others may be more difficult to obtain.
2010 UCLA Study and Map by Prof. Mike Manville and Prof. Donald Shoup (UCLA), reported on by the LA Streets blog. No link to the original study / seems hard to find even on the UCLA profiles of the researchers.
Total Vehicles In Urbanized Area: 6,433,000
Urbanized Area: (sq. mile): 2,980
Vehicles per Person: 0.54
State of California Traffic Census for Highways/Interstates
In the Netherlands: 7.3 million cars owned by private people.
Amsterdam: lowest car ownership, yet many vehicles in Amsterdam