The short answer is not much. At best, they may correlate to someone having a blood alcohol concentration over a .08. At worst, they prove nothing at all. To understand their meaning you must look at how they came into existence and who developed them. In the late 1970’s, NHTSA (the National Highway Traffic and Safety Administration) paid for some research to see if tools could be developed for law enforcement to identify people who are potentially DUI / DWI.