Completely agree with this. It would be interesting (and more valuable) to see the difference between mean or average car size over the years. Especially since (in Europe at least), there has been a rapid increase in SUVs, and, I am guessing, a decline in compact cars.
Will the cost of insurance and tax not outweigh the cost of a (monthly) ticket? And (especially older) cars must pass EU controls regularly for them to be road legal.
Considering this is a test to see if car users (they must park in a P&R) would use PT if it were free, it might just be a lead up for proposing it to be free for all.
To add, while the car users are not the ones that need this the most, a reduction in cars (even at the cost of ticket sales) could have positive effects for inhabitants of Aarhus on health and maybe even economic (some research shows that areas with fewer cars see local business thrive).