I remember the first time someone pointed out this lack of bug splatter to me and I was a bit scared about humanity's fate, but then someone else pointed out that our cars are a LOT more aerodynamic now. Not sure which side to land on here.
I have to say seems like wishful thinking. Sure cars have changed and aren't insect traps but at 80km/h bugs splatter on a windshield. The decline of insect biomass has been well reported, e.g. https://pubmed.ncbi.nlm.nih.gov/29045418 although not uniform. I've spent some time in northern areas where the bugs are bad!
This UK study used number plates, which haven't changed form between the two years (2004 and 2021), and have found a decline of just under 60%. Aerodynamics may have something to do with it, but I know from driving through insect-abundant areas recently that you still get plenty of splatter in modern cars.
The number plate is still attached to the car and thus the shape of the rest of the car affects how air moves over it.
How much is hard to say. Aerodynamics is just hard but basically as the car moves through air it pushes air out of the way and this air also pushes other air out of the way and thus elements next to each other will effect each other.
The aerodynamics of our ‘81 VW camper van haven’t changed in 43 years (basically a barn door). We get significantly less bug splatter on the windshield than, say, 20 years ago.
And though I can’t find the link again, it has been claimed that a more aerodynamic vehicle should get more bug splatter. I don’t remember why, attack angle maybe?
Another factor is that the right of way for highways is generally cleared further back (I guess for things like deer strikes). Insects have to go a long way out into a heat island to get to the center of the right of way these days.
