>Anyway, the emphasis, in my opinion, should be on behaviors that indicate loss of coordination, reflex issues, etc. not some arbitrary value.
Any such test is likely to be highly subjective and therefore open to bias and abuse. A breath alcohol content of 0.008% might be fairly arbitrary in terms of risk, but it's objectively measurable. A cop can claim that I was driving erratically just because he doesn't like the look of me, a jury can interpret dashcam footage unfavourably based on their prejudices, but a correctly calibrated breathalyzer doesn't lie. Drawing an a line in the sand between "sober" and "too drunk to drive safely" based on a biological marker of alcohol intake is almost certainly the fairest means of enforcement. There is of course the broader issue of who the police choose to stop and test, but there's no obvious technological solution to that risk of bias.
Any such test is likely to be highly subjective and therefore open to bias and abuse. A breath alcohol content of 0.008% might be fairly arbitrary in terms of risk, but it's objectively measurable. A cop can claim that I was driving erratically just because he doesn't like the look of me, a jury can interpret dashcam footage unfavourably based on their prejudices, but a correctly calibrated breathalyzer doesn't lie. Drawing an a line in the sand between "sober" and "too drunk to drive safely" based on a biological marker of alcohol intake is almost certainly the fairest means of enforcement. There is of course the broader issue of who the police choose to stop and test, but there's no obvious technological solution to that risk of bias.