Despite all the ad campaigns, it's still not illegal to drink and drive in Texas - even Waco, Texas. While that's good advice, it's not the law. You don't commit a criminal offense unless you drive while you're "intoxicated". That is defined as having an alcohol concentration of more .08 in your blood or breath, or not having the "normal use of your mental physical faculties".
So how do you know if you've had too much to drink and drive? Since alcohol alters your judgment, you aren't the best person to make that decision. I can't tell you how many people I've had tell me they were "fine" and did "great" on the field sobriety tests, and when you look at the tape they were barely able to stay standing.
While nothing is absolute, there are some general estimates you can make based on how alcohol is absorbed and processed in your body. Once ingested it will be absorbed, and then after a period of time your body will start to metabolize the alcohol, and it ends up being eliminated through the urine.
You can make a rough calculation of your blood alcohol content by knowing a few things. Generally, you process and eliminate the equivalent of one drink every hour; so if you only have one drink every hour you are going to be in pretty good shape - unless you're doing that over 10 or 12 hours and then you probably have other issues. There are a number of calculators out there which account for various factors, including weight and sex. Here's one from the National College of Drunk Driving Defense (which I'm a member of by the way), that will give you an estimate. Remember, it's just an estimate - If you are close to the limit I certainly wouldn't risk it; especially since the testing devices used are not entirely accurate; even blood tests have margins of error, so you could actually be under .08, and end up with a result over .08.
You also need to remember that the police officers are going to err on the side of caution. If they suspect you "might" be intoxicated you are going to get arrested and taken to jail. Even if you end up being released, that's not a pleasant experience. What that means is you need to err on the side of caution also. Don't chance an arrest - stay a little longer at the party, or have someone drive you home.
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