n deciding to impose a 15-month moratorium on mergers involving major railroads, the Surface Transportation Board said it wanted to restore stability to the rail industry and investor confidence in railroads. It appears to have accomplished neither.

Instead, it has made itself look less than impartial while reinforcing the impression that several major railroads are reluctant to compete.The decision, if it stands, stops in its tracks the proposed combination of Burlington Northern Santa Fe Corp. and Canadian National Railway Co. into what would be North America's largest rail system. BNSF and CN have each asked an appellate court to overturn the STB order.

We'll leave it to the courts to decide whether the STB has the authority to do what it did, or whether it overstepped its bounds. And the agency, sooner or later, will rule on the merits of the merger itself.

But the STB's rush to issue a merger moratorium - just a week after the agency's three commissioners listened to more than 150 people at a four-day hearing on rail mergers and the future of the industry - is worthy of note.

For openers, the agency appears to have bought in their entirety the arguments of five other major railroads that have been calling for a merger moratorium. They include Union Pacific, which suffered a service meltdown following its 1996 acquisition of Southern Pacific, and Norfolk Southern and CSX Transportation, which still are digging out of the congestion and service delays that followed last June's division of the former Conrail.

They claim that neither the railroad industry nor the shipping public has yet achieved the benefits of the last round of mergers and their attention should not be turned from working on the railroad to thinking of mergers.

They're right that there were service difficulties and that shippers had problems. But whose fault is that?

Moreover, the STB itself declared the service crisis in the West ended in December. UP is operating at pre-merger levels and its customers finally are realizing promised merger benefits. And service is improving in the East. All indications are that NS and CSXT soon will be at pre-June 1 service levels.

The railroads see this as a bad time for them to be forced into strategic responses - make no mistake, that means another round of mergers - to a BNSF-CN combination. Purchase premiums for past mergers and the extraordinary costs of restoring service have left UP, CSX and NS with weak balance sheets.

But where's the shipper in all this? Ed Emmett, president of the National Industrial Transportation League and no friend of rail mergers, had a pointed comment. He noted that the STB is always accused of failing to take the side of shippers. He suspects the moratorium may be wrapped ''in the mantle of a shipper-friendly decision, when in fact it was done more because of the other Class 1 railroads.''

It's hard to argue with him.

Moreover, the speed of the decision after the four-day hearing reinforces the view that the agency had determined what it would do even before the first witness appeared. That's unfortunate for the STB's credibility.

The railroad industry is not financially fragile, despite what the STB said. No railroad has had its credit rating cut. Nor have any had difficulty funding the largest capital spending binge in industry history. Stock prices are another matter. They reflect numerous factors: fuel prices, labor costs, the popularity of the ''new economy'' and the market uncertainty created by mergers and moratoriums.

It is not the responsibility of the STB, however, to protect either railroad stockholders or executives from self-inflicted commercial wounds. Nor should the regulator try to insulate companies from the working of the market place. It cannot succeed. The Staggers Rail Act of 1980 was government's admission that railroads would be better off in a market environment.

The STB appears also to have heeded the argument that a rapid industry consolidation to two systems following this merger would lead to re-regulation. But if rail-service quality meets customer expectations, there is no reason to assume re-regulation would occur. If anything, rail service might improve even faster if other railroads had to face the prospect of competing with an aggressive BNSF-CN.

There is nothing in the STB decision that reflects the contention that a BNSF-CN combination will offer shippers the benefits of greater market reach through more single-line service provided by the two most efficient railroads in the industry; or that because of the end-to-end nature of the merger, there is little likelihood of the kind of service disruptions experienced after other mergers. In fact, if BNSF and CN are to be believed, the only negative effects of their getting together might be the competitive impact on other railroads.

And that is the problem with the order. It imposes the judgment of Chairman Linda Morgan and Commissioners Wayne Burkes and William Clyburn Jr. on the transportation market. But it does so without due process.

No witnesses at the STB hearing were under oath, nor were any cross-examined. Ideas and positions were not challenged or tested. In reaching its decision, the agency ignored those whose views differed from its.

If the STB had allowed the BNSF-CN proposal to go forward, a record would have been created that would justify approving or rejecting the combination. No such record exists to support the arbitrary imposition of a moratorium.

The STB and BNSF-CN now are in a legal fight. We hope that all railroads, however, will continue to focus their efforts on improving the service they provide their customers. Like walking and chewing gum at the same time, rail executives should be able to operate railroads and deal with merger issues simultaneously.