IT'S STRICTLY FOR your own good, but you should know that police in Maryland have a way of looking down on you at all times--and it's paying off. If you're driving this weekend for any reason (and there are plenty that leap to mind right about now), be advised that the state police are not only all over the roads but also in the air, checking your speed in imaginative and legally definitive ways. Be thankful--the result seems to be that people just aren't dying the way they used to on those highways.

If the traditional safety sermons tend to fall on deaf ears, maybe numbers talk: in 1980, traffic accidents in Maryland were killing about two people every single day of the year. But unlike too many other states, Maryland's death tolls have been decreasing. Last year, "only" 595 were killed. The difference may well be related to the latest super-crackdown--with air surveillance, checkpoints for drunken drivers, marked and unmarked cruisers and now big computerized billboards that will flash the driving speed of a car leading a group of other cars with a warning to "Check Your Speedometer."

How you drive, of course, is only part of staying alive. Sobriety behind the wheel, using seat belts and sturdy infant seats, maintaining prudent speeds and--truckers, please note--care not to tailgate, are all elements of auto safety. But often the most unpredictable, dangerous threat is another driver who challenges your mental and physical reflexes in terrifying ways.

Perhaps you have come to suspect that a lot of drivers are breaking the speed limits. You're right: state highway surveys have shown that the average speed of motorists traveling 55-mile-an-hour roads is 60.5 miles per hour. During the year ending last Sept. 30, 44.4 percent of Maryland motorists had exceeded the speed limit. Moreover--on more number--the decrease in the rate of fatalities in Maryland has a catch to it. The percentage of those killed on highways with a 55-mile-an-hour limit has risen, from 17 percent in 1980 to 20.3 percent in 1982.

Needless to say, the police in Virginia and the District also will be out and about this weekend with a job to do. They can use all the help they can get.