There is good news in the battle against crime. Washington area jurisdictions all report that in the first half of 1983 serious crimes were significantly down as compared with the same period in 1982. Everyone should pause to congratulate the local police forces, and then urge them to do more.

The figures include homicide, rape, robbery, aggravated assault, burglary, larceny and auto theft. Percentage decreases range from 16.2 in Montgomery County to 8 in Arlington. In the District, the drop was 11 percent. These improvements are part of a nationwide trend that began about two years ago and is due largely to a declining population in the trouble-prone under-25 age group. As bad actors get older, they either find themselves locked up for a good while or, more likely, mature out of their antisocial ways. A few die from weapons or needles. Some may be rehabilitated.

Absolute levels of crime remain intolerable. In the District during the six-month period, there were almost 100 homicides and more than 6,000 burglaries. There are no good measures of the anxiety and fear. In a sense, it is rather remarkable that most citizens are conditioned to expect the levels of violence, disorder and fear that exist. After all, personal safety is a human right. One hopeful sign, and an apparently important contributor to the improving figures, is that more communities are organizing themselves against crime. What they expect, they will no longer accept. The results are more political pressure on police departments and politicians, and neighborhood self-help efforts, which, with police assistance, can be effective.

Officials also point to better police strategies, such as a focus on repeat offenders and expanded narcotics teams. Stiffer pretrial detention procedures, bail practices and sentencing may be playing a role. It is impossible to say, because the criminal justice system is so complicated and the factors thought to influence crime rates so numerous. When it's hard to make a strong case that any particular strategy helps or hurts, and when budgets are tight, there is a continual danger that crime will slip as a government priority. There will be flashy raids and sweeps, but inadequate resources for police, courts and corrections. Only a persistently aroused public can prevent that. The new figures, showing modest improvement, should be taken as encouragement to fight harder.