To play it safe, when should you start counting the time to sober up?

Starting to count the time to sober up after finishing the last drink is the most effective and accurate approach. The body needs time to process and eliminate alcohol. Alcohol is metabolized at a specific rate, typically about one standard drink per hour for most individuals. By beginning your countdown only after the last drink, you can better estimate when your blood alcohol concentration (BAC) will decline to a level considered safe for driving.

The other choices may lead to a misunderstanding of how alcohol affects sobriety. For instance, counting an arbitrary hour or eating food may give a false sense of security and could encourage someone to drive too soon, as food does not significantly speed up alcohol metabolism. Similarly, counting during the drinking session does not accurately reflect when the effects of alcohol will diminish since intoxication continues to increase until the last drink is consumed.