https://www.jospt.org/doi/full/10.2519/jospt.2016.7049

I was listening to a podcast on the subject earlier this week, while sliding my way to work on the first snowy, slick roads of the season. Motor vehicle accidents clearly occur year around, but the risk factors are about to increase for several months.

The article did not bring anything exceptionally new in the clinical dilemma of understanding the overlap of neck injuries and concussion in rear end motor vehicle accidents, but it highlighted a couple of important reminders:

The position of the head rest in a rear end collision is a big determining factor of the forces that will be applied to the upper spine and head. The headrest should be slightly above the occiput to block the head from hyperextending. If the headrest is lower than the occiput, it creates a buckling point for the head to sharply and violently hyperextend, a risk for both spine and brain injury.
Females tend to have longer and less complete recoveries than males in equal accidents, since the circumference of the neck to the head is on average smaller, and the head acts as a fulcrum weight on the lower neck during flexion and extension.
The force applied to the head and neck in rear end collisions at speeds as low as 10 MPH are equal to the hit taken by a football quarterback at full speed, if certain mechanical elements of the crash are not favorable, such as the position of the head rest and head rotation at the time of impact.

Not everyone in a rear end collision will have a serious neck injury, but many will have milder injuries that will linger on and come back to haunt them for the long run. In case of doubt, get checked.