This was a news story in itself [1]. It was attributed to increased driving, encouraged by economic factors such as higher employment and lower gas prices.
[1] http://www.npr.org/sections/thetwo-way/2016/02/18/467230965/...
https://en.wikipedia.org/wiki/Transportation_safety_in_the_U...
In its own early estimates that were released late in 2015, NHTSA reported seeing a 3.5 percent rise in vehicle miles traveled in the U.S. But it also said the fatality rate — the number of deaths per 100 million vehicle miles traveled — was rising at a slightly higher pace of 4.4 percent.
Interesting - I always assumed that the increase in road deaths was at least largely due to increased cellphone usage, resulting in distracted drivers.
https://mobile.nytimes.com/2016/11/16/business/tech-distract...
Florida and Georgia combined saw a +190 drunk driving fatalities in the same period.
EDIT: found a more specific report about electronic device usage: https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/...
[0]: https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/...