THEY DON'T flash on neon "No Vacancy" signs when a jail or prison fills up, but at the rates people are checking in these days, something is going to have to give -- other than the taxpayers. All over the country and right here in the region, the same question keeps coming up for the begging: Will people continue to pay for bigger and bigger detention facilities, or would they prefer to consider better ways to incarcerate those who are dangers to society while doing something more productive with non-violent offenders?

Many jailers and prosecutors reflexively opt for bigger jails and prisons -- and hang the costs. But taxpayers in various areas -- Fairfax County being the most notable local example recently -- are begining to think twice before they agree to shell out millions for bigger jails at a going rate of anywhere from $50,000 to $75,000 a cell. Voters in Fairfax are thinking for that second time right now, having rejected one jail-expansion bond issue already. A county government task force has examined alternatives to relieve crowding at the jail, which is only three years old and already jammed, and recommendations include a number of sensible steps that should be taken before any blind approvals are given for multi-million-dollar expansion projects.

It is not a matter of flatly rejecting an expansion, but a look at the math shows why other moves are essential: unless changes are made in jailing procedures, the jail population may well continue to swell with the new cells, as the present county jail did shortly after it was opened. In addition to judicious use of work-release, drug and alcohol treatments and community service programs for non-violent offenders, every effort should be made to avoid locking up people charged with misdemeanors in expensive or crowded cell space.

The task force did not simply dust off familiar generalizations about releasing huge numbers of prisoners and bringing a halt to the building of any more detention facilities. Instead, the recommendations deal with specific in-county possibilities, such as renovation of the old jail as a temporary work-reliease facility; establishment of a relocated, secure and staffed pre-release center; and a weekend court to speed arrest and release procedures.

Along with these measures, the task force concludes that, yes, an expansion of the jail is called for -- and that, no, none of the above will come cheaply. So another referendum may be in the offing. But if the county supervisors expect to get it past the voters, they would be wise to ensure that any expansion of the jail is contingent on approval of a broader corrections program along the lines of the task force recommendations.