Actual scientific studies show that measurable impairment begins at .02, is absolutely measurable at .035, and prohibits numerous vision, motor skills, and cognitive processing abilities associated with driving at levels between .04-.05.
The reason the .05 BAC number was chosen is because at that point, anyone in a scientific study has eroded their own skills to the point that it is without any doubt provable that they are incapable of performing safely.
In other words, you are already "drunk" at .05, and incapable of performing up to your own standards on any test that they give.
So, if the govt is supposed to be involved in these acts of monitoring, then .05 is the highest level that should be passed over. Most studies would indicate .035 as a "scientifically provable" threshold.
https://pubs.niaaa.nih.gov/publications/aa25.htm [links to many studies in the footnotes]
http://www.tac.vic.gov.au/road-safe...nk-driving-statistics/effects-of-alcohol [the accident commission notes that studies show multi-tasking impairment begins at .005, and most other impairments are provable at .03]
https://healthblog.uofmhealth.org/wellness-prevention/how-alcohol-impairs-your-ability-to-drive [scroll down for an easy chart showing what impairments happen at what BAC levels]
https://www.onhealth.com/content/1/alcohol_impairment_chart [chart for body weight and BAC levels and impairment]
