ONE OF THE finest traffic jams of the spring season has been brought to our attention by a number of motorists who spent too much of their Sunday inching along Maryland's Route 50 in an excruciating attempt to return from the Eastern Shore beaches.

Before anyone leaps to a traditional conclusion, it was not the fault of the Bay Bridge. Nor was that other infamous obstacle along this beaten path-- the Kent Narrows Bridge--the biggest problem either, even if the repairs there do seem to have taken the better part of an eon. Traffic there was only backed up for a few miles or so at a time.

No, for this first spectacular weekend of the warm season, Maryland's construction wizards chose Sunday afternoon to turn two critical highway lanes into one, right by the overpass at Routes 50 and 301--which backed up traffic for a good 13 miles for most of the afternoon and evening hours, according to the state police, who did their best to assist motorists running out of gas, food and/or patience during the two hours or so that it took to crawl the highway stretch leading to the overpass.

Maybe no one in the state department of transportation noticed that on Friday evening and Saturday morning, a large number of travelers did seem to be taking advantage of an exceptional weather forecast to get out of town. Or maybe it never occurred to anyone in charge that a large majority of these vehicles might just be coming in the other direction on Sunday.

But if tourism is a serious industry, and if the joys of the Eastern Shore are to remain alluring to anybody other than property owners, Gov. Hughes had better order some quick fixes during off-hours to get weekend traffic moving reasonably. We're told that the Kent Narrows Bridge mess, which has been bad enough since last fall, will be gone by May 15. But so will many of the tourists, unless the whole route is open for business by Memorial Day.