LEAVING NOW as secretary of transportation, Elizabeth Hanford Dole has proved to be a loyal, top-level administrator -- popular on the political circuit and, according to the president yesterday, "invaluable." Though her stewardship has drawn its share of criticism, Secretary Dole can point to a number of accomplishments over a period of great changes in federal oversight of transportation in the air and on the ground.

In these last summer months of public discontent with airline service and of anxiety about safety in flight, the administration's record has been far from perfect. Still haunting airline safety policy was President Reagan's 1981 firing of striking air traffic controllers and his refusal even six years later to consider rehiring any of them. However one may view those decisions, the administration was slow to acknowledge a need to hire and train more controllers -- and to install sophisticated equipment at facilities across the country.

During Mrs. Dole's tenure, the industry underwent a rapid expansion after the 1970s congressional deregulation of fares and routes, and then still more structural transformations as many newer, smaller airline companies were swallowed up by larger lines. Meanwhile, the number of people able to travel by air increased dramatically, a development afflicting flight schedules, near-collision reports, baggage foul-ups and overbooking.

The fashionable but sloppy explanation for these troubles has been that deregulation bombed and ought to be reversed. But as Secretary Dole has insisted, safety has not been deregulated. Better service, more truth in scheduling and better procedures for inspections and other safety measures can be -- and have been -- ordered.

There are other issues in which Mrs. Dole's leadership and lobbying paid off. Conrail was sold, National and Dulles airports were turned over to regional control, and Union Station was brought back from the dead.

It is important that the administration find someone quickly to take over a department that is in the middle of so much urgent business. Mrs. Dole was, as usual, conscientious in concluding that she could not give the amount of time she wished to her husband's campaign and still run the Department of Transportatio