That also correlated with the times that a number of states began to legalize marijuana for recreational use[1]. There are studies looking at this relationship and finding a correlation between road death increases and marijuana legalization.

[1]: https://en.wikipedia.org/wiki/Legality_of_cannabis_by_U.S._j...

[2]" https://www.usnews.com/news/health-news/articles/2022-07-19/...