AFTER 21 UPBEAT YEARS as the face, voice and resident Pollyanna of Washington's regional transit authority, Cody Pfanstiehl intends to retire, effective, he says, at of the "close of business --the public's business--Sept. 10." People who have worked with or around this ever-genial director of public affairs to get to the bottom of a Metro story must confess to having marveled at his exuberance and to having appreciated his respect for the public's interest in knowing what's going on at any given hour.

There were times, in fact, when Mr. Pfanstiehl's open disclosing of Metrofacts had his own colleagues frowning or fretting--such as the time he related the various salaries of the staff, insisting that what public officials are paid is public business. The man obviously likes the buses, subways and people in them; he waves at drivers and talks to anyone within earshot.

It is unclear precisely which of the apparent dozen or so Cody Pfanstiehls is retiring: the one people see and hear on the air explaining delays and other breakdowns, the one in the hard hat who leads guided tours of new tunnels, the one who speaks to community gatherings, or the one who writes all those corny memos and press advisories. Perhaps it is the one who only one week or so ago startled passengers on a subway car that kept stopping and starting on the tracks near Union Station; up he got, walkie-talkie at the ready, to announce that there had been a report of a man walking on the tracj. "Don't know why he'd want to walk on the track," he said, "when he could be riding in a nice air-conditioned car."

We'll miss Cody Pfanstiehl.