The effects of various blood-alcohol-content percentages on behavior are not a matter for debate in American legislative halls. Science long ago settled the issue. What remains to be decided is whether states want to continue allowing people with alcohol impairments to legally drive.

Utah and other states should lower their legal drunk driving limits from the current .08 percent to .05 or less. That has been the position of this newspaper for at least 20 years. It would save lives and eliminate much of the guesswork in deciding whether one has had too much to drink. This week, the National Transportation Safety Board voted to recommend the .05 level, which may begin to move serious discussion in that direction.

Don't count on quick action, though. It took decades to get all states down to the .08 level, and then only because President Bill Clinton signed a law that removes 4 percent of a state's federal highway money allotment if it refuses to do so. We don't advocate that sort of heavy-handed approach from Washington toward a .05 limit, but it is significant to note that drunk-driving related deaths have been cut in half over the past three decades to coincide with lower limits, and that a cultural stigma against drunken driving has grown.

To understand why the legal limit should be lowered, you need to know what happens between the levels of .05 and 08. Studies show that, while concentration levels begin to be impaired at a .03 blood alcohol level, at about .06 one begins to lose reasoning, depth perception, peripheral vision and glare recovery. Emotionally, one begins to lose inhibitions and the ability to properly calculate risks. While reflexes and reaction times may still be at safe levels, these other changes pose significant safety risks on the road.

The effects of a lower DUI limit also are fairly easy to predict, especially since the United States is among the few nations worldwide that persist in maintaining such a high limit. Australia, for example, recorded a reduction of between 5 and 18 percent in traffic fatalities across its provinces when it moved the limit from .08 to .05.

Not surprisingly, restaurant owners and the beverage industry oppose tightening the definition of drunken driving. It is difficult, however, to argue against the NTSB estimate that as many as 1,000 lives could be saved nationwide each year if the limit was uniformly lowered. This 10 percent reduction would be well worth the effort.

In Sweden and Norway, the legal limits are .02 percent, which is just high enough to account for false positive tests and naturally occurring alcohol in the body. Quite simply, diners do not need to fool with guesswork in those countries. The same can be said for diners in .02 Estonia, The Netherlands, China, Israel, Poland and Puerto Rico. They may have to annoy themselves with finding rides home after only one drink, but drivers can appreciate a higher level of confidence in the abilities of others they encounter on the roads.

Ultimately, the answer to drunk driving fatalities lies not so much in blood-alcohol limits as in deterring people from driving after drinking. Stricter limits, however, make it easier to get that message across. Utah, a state that already enjoys low DUI rates, ought to lead the way toward reduced limits and even safer roads.