IT'S STILL TENTATIVE, subject to memberhip review and a vote tonight, but an agreement reached between teams of negotiators from Metro and Local 689 of the Amalgamated Transit Union appears to be a model package of tradeoffs that should benefit not only labor and management but the paying public as well. Above all--and of importance to every party involved--this would be the first contract put together and agreed to by the union and the current transit system, instead of having been dictated by binding arbitration.

In addition, Metro would achieve new and necessary curbs on wages--including a freeze until next May--and on cost-of-living provisions by eliminating compounded quarterly increases. In return, Metro's employee members of the local, part-time as well as full-time, would win new benefits, including a significant take-home bonus in the form of pension payments assumed by the management.

Employee pension contributions currently amount to 5 1/2 percent of pay; this would be added to take-home pay as of July 1 of this year. Then next May, and again on May 1, 1985, instead of the old cost-of-living computations, employees would receive general increases of 6 1/2 percent. Also in May 1985, they would receive 80 percent of any difference between the last general increase and the last annual increase in the consumer price index. This same CPI formula would be used in April 1986 to determine the effective wage at the end of this agreement.

Another key management change would allow Metro to raise the number of part-time bus operators from 10 to 15 percent of the total force. For bus scheduling--and just as important, for savings on the payroll--this is a significant gain.

As in almost any negotiated agreement, this one falls short of what either side (or the public) might wish for. Employees could always hope for more money, of course, even if inflationary settlements may mean no real gains. In turn, Metro and the public could always hope for smaller wage arrangements, greater insistence on productivity improvements and even more cuts in full-time positions. Instead, this package represents a thoughtful and fair balance of concessions and improvements--as well as a better labor-management spirit than has been the case when arbitrators have dictated the terms.