Surely even our 6-year friend David could have told us why the chicken crossed the road-but was that all that had impelled our party of 13 parents and children, along with roughly 50,987 other people, to walk across the Chesapeake Bay Bridge the other Sunday? Or was it that we could do so without paying the toll?

The bridge did take its toll on some, judging from the expression of one woman who finally kicked off her heels at mid-span and forged ahead barefooted. But by and large, give or take an occasional cranky toddler or glazed teen-ager, here was a mob on a lark, reveling in an essentially simple-minded, 4.03-mile mission.

The view from the bridge? Not today, for the higher we got (which our brochures told us would peak at 186.5 feet above mean high water), the cloudier and clammier it got. Fair enough, I said to myself, since the trustly movei camera wasn't working anyway.

Besides, action shots would have been few, for activities are somewhat limited on the bridge, even though the Maryland Transportation Authority had thought of certain things one might want to do along the way, including bellying up to an ice-water bar.

So what was it that made this such a kick? For one thing, you can feel athletic without being so. You can climb high in the sky without scaling any mountain. And to the joy of those of us who haven't yet pledged our souls to jogging, there's a pedestrian rule: You're not allowed to bike, run or jog on Bay Bridge Day.

Skateboarding, pets and food are prohibited, too, though there wasn't any mention of dancing, tumbling or walking on your hands.

The whole walk idea first suggested in 1974 by a Scout leader from Towson, when he heard that one span had been closed for maintenance. When the first Bay Bridge Day was held the next year, about 20,000 people turned out, and the crowds have been growing ever since.

This year, there were people in wheelchairs, infants on backs and, just as some of us were beginning to tire, stirring sight: on crutches, taking it one small step at time and loving it, 80-year old Albert Baker, a former professor of religion who was with a church group from Largo. All of sudden, our 26 feet didn't hurt at all.

The real fun of its is the thrill of doing something you're usually not permitted to do and living to tell about it. It's getting to go backstage; being allowed for the first time to stay up all night; hopping up at the crack of dawn to bike on the boardwalk.

That must have been why, when jovial Sgt. P. P. Wallace of the Toll Facility Police was handling out suitable-for-framing certificates of participation, I wanted one as badly as the kids did-though I tried my best to be nonchalant.

Granted, Chesapeake "Bay Bridge Day" doesn't rank with the Boston Marathon, the C&O Canal Hike or your basic sacling of the World Trade Center. The exhilaration here, however short-lived, has not to do with any joy of conquering. Perhaps the fact that there isn't much point to this event contributes to its popularity. After all, did anyone ever ask that chicken to justify its crossing?