Cars are much bigger (easier to accidentally hit stuff with them), taller (harder to see things at street level) and heavier (take longer to stop and hit much harder) and smartphones greatly reduce driver attention.

I went googling to find evidence to disprove your statement about cars, and I found that you are correct. Though the trend slope is pretty shallow in the graphs I found, I can believe small increases have outsized effects.

...and the smartphone part I obviously wouldn't dispute.