(CNN) -  Even if they don't admit it, most people know when
they're hammered.  But they may not always know when they're
legally drunk.  If states heed the new recommendations of the
National Transportation Safety Board, it will be easier for
motorists in the U.S. to be arrested for drunken driving. The
NTSB wants states to reduce the blood-alcohol content threshold
used by law enforcement to prosecute drunken driving from 0.08
to 0.05.  In plainer language, that means drivers could be
subject to arrest after downing as few as two recent drinks.
How do you know when it's safe to get behind the wheel and when
you should hand the keys to someone else? Here are some tech
tools that can help.  Blood-alcohol calculators  If you have
access to a computer, there are sites that can estimate your
blood-alcohol level. You enter information such as your body
weight, the types of drinks you've had and how long you've been
drinking, and these online calculators will spit out a number.
For example, a 180-pound man typica