Your other friends MUST come over, must join you in the backyard pool for a dip.

Natalie, you say into the mouthpiece, come over.

But Natalie can't drive, and neither can you, and therein lies the impediment to nearly every summer social opportunity.

You're trapped, at the mercy of parents and older siblings who haul you from place to place at their convenience--not yours.

But if you are 15-year-old Mary Cline--polite yet persistent--you press on.

You hang up with Natalie. You look at Stephanie and think: Kelly.

Kelly, Stephanie's older sister, drives.

It's 11:30 a.m. The pool's sun-kissed water beckons. You, in bare feet, shorts and tank, dial Stephanie's number.

Is Kelly there?

Kelly, your would-be chauffeur, is still snoozing.

"We can't wait until Mary gets her license," Stephanie says.

A driver's license may be the most revolutionary possession a teen-ager can acquire.

Because once that license is tucked into a wallet, there's no more asking Mom or Dad to please pick you up from the movies at 11, knowing full well they go to bed by 10.

No more trying to figure out if your friends can get to the mall, which isn't far away but might as well be on the moon if nobody has a ride.

And no more worries that someday you'll find your butt on the plastic seat of a yellow school bus, getting hauled to class in the uncoolest of rides.

Mary Cline, a junior at Stafford High School, keeps a busy schedule--one that requires much transportation. She plays tennis for the school team. She volunteers at Mary Washington Hospital. She baby-sits. And she hangs out with her friends every chance she gets.

So Mary has developed ride-sharing skills that would dazzle the most resourceful Fredericksburg-to-Washington commuter.

She knows who has a license, who has a car and who works when. Still, she can't always get where she wants, and neither can her friends.

"If we want to do something during the day, we usually can't do it unless, like, our sisters will give us a ride," Mary said one morning. "But usually they have to work, or they're too lazy."