PHILADELPHIA'S cops and judges are right - a focus on repeat offenders can mitigate prison overcrowding.

More crowding and more spending aren't predestined if the city adopts some of the promising programs popping up nationwide to help jail inmates transition back to the community and if the droves of "frequent fliers" who make the jail their home get help fast.

Although a new (and not-yet-released) study by Paul Heroux, at the behest of ex-Philadelphia Prisons Commissioner Leon King, suggests that increased admissions and longer stays are keeping local jails overflowing, recidivism is equally a problem.

Grounding those repeat offenders will improve public safety and save money.

A 2006 report by the Urban Institute for the Philadelphia prison system found that nearly four out of five prison releases from 1996 through 2003 were re-releases. Seventy percent of prisoners released in 2003 had "been there, done that" in the previous eight years, and about one in every five prisoners released were coming out for the second, third, even fourth time. If the city can identify the oft-imprisoned and provide services to assist their return to the community, the city will save money and otherwise wasted lives.

Some cities are finding that concentrating on cutting the number who frequent jail and use other services can slow the revolving door, cutting the jail population and saving millions.

In New York, where researchers compared those in homeless shelters with those in jail, at least 900 people had been in jail four or more times and in shelters that many times over a five-year period ending in 2006. Early results from a city initiative to place these high-cost nomads in permanent supportive housing halved their jail stays. In Seattle, 125 mentally ill people who bounced in and out of jail and averaged 21 emergency-room visits a year cost taxpayers more than $3.2 million in hospital bills alone.

Corrections systems may balk at spending money for community-based pre-release programs. But it's just too expensive to define public safety narrowly. Given economic pressures to cut the jail population and political pressures to improve public safety, the choice is between which approach to programs aimed at frequent users is best, not whether to launch or expand them.

Maybe Philadelphia can learn from Allegheny County. A light bulb came on when corrections administrators, in collaboration with county health agencies, found that 64 percent of women and 43 percent of men in the jail from 2003 to 2005 received services from the Department of Human Services and 72 percent of those booked five or more times over two years were also in at least one such program. After programs were developed to assess and address detainees' risk and needs, recidivism dropped by half and saved the county $5.3 million.

So what are the ingredients of re-entry programs that work?

FIRST, individually assess the needs of all inmates and count their entrances and releases before they head out the gate.

Second, assign frequent fliers a case manager to coordinate housing, employment, health and mental-health services.

Third, address the dire need for housing for this population by providing short-term and long-term transitional housing, as well as permanent supportive housing. Permanent supportive housing has been shown to be highly successful with the seriously mentally ill who cycle in and out of jails.

Fourth, train the staff of community organizations and corrections agencies to understand the roles and responsibilities of each and the range of services that are available for hard-to-serve populations.

Finally, appoint an intermediary to manage the program, reinforce the vision, and nurture collaboration and democratic decision-making.

Even without new programs, city leaders and researchers should analyze what data they have to set re-entry priorities, develop evidence-based programs, and document successes.

Real progress requires figuring out where services will be most effective, where savings are possible and which services and agencies will benefit. Ignoring the re-entry challenge jeopardizes the city's crime plan and wastes dollars and lives. *

Caterina Roman and John Roman are justice-policy researchers with the Urban Institute in Washington, D.C.