WASHINGTON'S police are preparing to crack down on the scourge of the streets, the red-light runners. Maybe they will bring back the difference between red and green. As our readers have been volunteering regularly in the letters column, there are countless theories as to why more drivers have been ignoring traffic lights: the lights don't work well, right-on-red has cheapened the color code, the driver behind you is going to ride right over you if you stop, nobody cares anymore anyway . . . you name it.

The trouble is, none of this excuses the lawbreaker or protects the innocent. Traffic fatalities are up. Radar-equipped units will be watching high-violation areas in each of the city's seven police districts starting next month. The roving enforcement units will be operating only about four hours a day, Mondays through Thursdays. Other police teams will be on the prowl anytime, spot-checking intersections just the way they have for drunk drivers.

There is more good news for the various corners of the city: One of the country's oldest traffic-light systems will start being replaced soon. It can't be too soon. It is a miracle that the current system works at all. It was installed in the 1950s and relies on radio messages that are supposed to switch and coordinate the lights. Thanks to a marvelously innovative crew of repair people who have begged, borrowed and pirated ancient radio parts to keep the system taped together, the lights still do change now and then. But the supply of luck and parts is dwindling -- and computers will be taking over.

Obviously even the best traffic- light system and police vigilance can't catch all the violators. But if the message can get out to residents and tourists alike that Washington is not taking kindly to red-light runners, lives can be saved. Who knows -- maybe sensible driving will become fashionable again.