NORTHERN VIRGINIA commuters are constantly challenged by frustrating regulations, detours and computerized gimmickry, all in the name of improved traffic flow or environmental bliss. But they may have found a friend in Washington. Transportation Secretary Elizabeth Dole, noting the many complaints about plans for a $22 million ramp-metering system on Shirley Highway, has agreed to review the project. The news is welcome not only to drivers but also to local officials who have been complaining about the ramp idea for some time.

Fairfax and Alexandria have been threatening suits to stop the Virginia state highway authorities from installing this system, on grounds that it will create even worse traffic backups than the monumental ones that already occur daily on many of those ramps. In addition, they have suggested that these alleged traffic-flow controls will send much traffic back out to congest neighborhood streets.

State Highway Commissioner Harold C. King has been insisting that the computerized control system would improve safety and efficiency and that, anyway, it's too late to stop the project. But Mrs. Dole's people say the system should be reviewed carefully, and the process could mean either a delay or cancellation of it. Such a review is sensible and fair. Fairfax Board of Supervisors Chairman Jack Herrity, who thinks so too, put it this way: "This is a solid chink in the armor of this roadblock that is driving down the street."