One of the greatest dangers for cyclists in any city is the risk of being run over at intersections by right-turning motor vehicles. (Left-turning in the UK.)
Copenhagen has come up with a good solution to this problem. At a few intersections (only a few when I was there) they have installed separate traffic lights which are set to make right-turning cars stop while bicycles go straight ahead, and visa-versa.
This is no doubt more expensive that just letting cyclists be squashed to death, but the expense is totally justified and in any case is just a small fraction of the huge amounts routinely spent on infrastructure for motor vehicles.
Another solution to the problem of cyclists being hit by right-turning vehicles is to paint blue stripes on the street at dangerous crossings.
At many corners, the blue stripe extends only halfway across the intersection, only through the most dangerous area where cyclists are liable to be hit by right-turning vehicles.
These blue stripes in Copenhagen are the equivalent of the dark red stripes in parts of Germany, Belgium and Switzerland, and the white arrows on the streets and squares of Paris.
The city of Copenhagen has commissioned research into the effectiveness of these blue stripes. The conclusion is that there should be one and only one blue stripe per intersection. One blue stripe effectively reduces accidents, but two or more blue stripes are counter-productive because they confuse car drivers.
My photos in this post are from 2009. I revised the text in 2019.