Each state sets its own speed limits, and it also decides what to do about drunk driving in the state. The table below shows how states define drunk driving, whether they immediately suspend the driver's license for first-time offenders, how long offenders have to wait until they can drive again, and whether drunk drivers face having their vehicles impounded or fitted with an ignition interlock. Administrative license suspensions happen independent of the criminal process, which means drunk drivers get taken off the roads that much more quickly.
Interlocks analyze a driver's breath and disable the ignition when they detect alcohol.
You'll notice that there are different figures for adults and youths. That's a result of the zero-tolerance measure passed by Congress in 1995, and subsequently by the states. It sets a different standard for drivers under the age of 21, who cannot legally drink alcohol. Per se is Latin for in itself , or intrinsically . Other factors would include slurred speech, unsteady gait and all those other things that the police look for when they give those roadside tests.