1. Auto travel has grown (cited by the article).
2. Vehicles have far more safety features today, but I suspect they are increasingly unsafe in many high-impact collisions as fuel efficiency standards have pushed manufacturers to build lighter cars.
3. We've seen an awful decline in driving skills in general, with distracted driving a particular factor. Add our aging driver population to the mix, too.
4. With the growth of walking and cycling in urban areas all over the country, there is more exposure to injury and death among people who have almost no protection in a crash. Dangerous designs in many roads that have crosswalks or bike lanes aren't helping, either.
“Dangerous designs in many roads that have crosswalks or bike lanes aren’t helping, either.”
The local “progressive” county commission pushes cycling and walking as viable alternatives to auto commuting but without providing the funds to fix the streets to make these alternatives safer. Pedestrians and cyclists are lured into a false sense of safety just because there are crosswalks with pavers or some painted bicycle lanes. Through distracted drivers into the mix and it is a recipe for increased carnage along commuter routes.
I'm going to say that is not a factor. Cars are actually not lighter today than they were 50 years ago. There is video out there of a IIHS crash test of a 2009 Chevy and a 1959 Chevy in an off-set collision. The 2009 busted into a million pieces, but the driver would have lived. The 1959 busted up, too, and the driver would have died instantly.
I looked into it further. The 1959 looked bigger and heavier, but that was due to perception. It was slightly longer, but no higher, and no wider.
It was also within 200 lbs of the 2009 Chevy in weight.
The weight difference between the two cars was insignificant in the crash.
1959 Bel Air 4-door
Weight (varies) 3,615 to 3,660 lbs.
Length - 210.5 inches (17' 6.5").
Width 79.9" (6' 7.9").
Height 54'-56'.
2009 Malibu:
weight: 3,415 lbs (200-245 lbs lighter)
Length: 191.8" (15' 11.8") - 18.7" shorter.
Width 70.3" (5' 10.3") - 9.6" narrower
Height 57.1" - 1.1 to 3.1 inches taller.
Sources: Malibu http://www.edmunds.com/chevrolet/malibu/2009/sedan/features-specs/
Bel Air: http://www.oldride.com/library/1959_chevrolet_bel_air.html