I remember this particular data point being refuted by cars becoming more and more streamlined. The bugs don't die anymore, they whoosh over ;) Anecdotal: after driving at normal speeds, very few bugs indeed, also compared to 30 years ago. After prolonged driving on the autobahn at high speeds (200kph+) there are more bugs on the front of my car than ever.

I am quite sure there is a significant decline in insects, and we should be worried and act upon that, but the bugs on car thing is not the best way to measure.