You can measure mixed risk like this in hours exposed, since the outcome of a car and bike trip in Denmark is the same (you get to work or whatever). That will also be fairer to cars, since I suspect there are more deaths per KM for cars.
I ride my bike just shy of 40kms per commute, the same amount I would drive.
I find it very dubious to assume that cars drive the same amount of kilometers as bikes in the Netherlands...