You have nothing but milk and butter in your basket, so you scurry over to the empty checkout lane. But a woman steering a grocery-laden cart wins the race. You fume, and wait in line another 10 minutes.

Can technology save you?

The supermarket chain Harris Teeter Inc. hopes to turn grocery shopping into a self-service experience similar to the one that transformed the gas stations.

On Wednesday, the grocer will introduce a self-service checkout lane at a store in Arlington's Ballston community, the retailer's first supermarket to open in the Washington area. The system is one of the more advanced in the grocery industry. It allows shoppers to scan their own groceries, bag them and then check out without having to wait for a cashier. Harris Teeter's system accepts bills, coins, credit cards and debit cards.

"It's really designed for the consumer," said Sonya Elam, a spokeswoman for retailer, based in Matthews, N.C. "It's no different than the trend today with the gas service pumps. People like to pump their own gas. We find people also like to do their groceries themselves."

Super Fresh and Winn-Dixie Stores Inc. also have opened self-checkout systems in several stores. But those retailers' systems do not accept payment, so customers must pay a cashier after scanning and bagging their products.

Not everybody likes the new checkout technologies. The systems tend to draw younger patrons, who seem more comfortable using computers. "Most people like it, but older people don't seem to use it that much," said Doug North, manager of a Super Fresh store in Fairfax that recently opened with three self-service checkout lanes.

So far, U.S. supermarket have not been able to prove that self-checkout lanes improve the entire buying process, industry analysts and some retailers said. The best cashiers, they say, can ring up sales and bag items faster than customers.

"I think it's an interesting consumer option," said Jeff Metzger, an expert on the area's shopping scene and publisher of Food World in Columbia. "On the Richter scale of 1 to 10, it's about a `1' in terms of affecting the whole tenor of the stores."

Giant Food Inc. and Safeway Inc., the Washington area's two largest grocers, don't seem to be enthused by the self-service concept. Giant has no plans to dabble in self-checkout lanes. And Safeway, meanwhile, tested a rudimentary self-service aisle 10 years ago at a store in Greenbelt and abandoned it.

"We experimented for a few months and decided it wasn't something we would do," said Gregory TenEyck, a Safeway spokesman. "I'd summarize everything by saying Safeway's definition of good service is having [employees] involved in the checkout process."

TenEyck isn't sure whether customers really like the idea of bagging their own groceries. And even if consumers relish the extra work, some grocers aren't sure they want them to do it.

Shoppers Food Warehouse, for example, has a "bag-it-yourself" policy that fits in with the retailer's lean approach to business. But on busy days, some cashiers can barely hide their impatience with slow-moving customers. Executives with Supervalu Inc., Shoppers Food Warehouse's new owner, want the retailer to ditch the old system.

So far, self-checkout systems are so rare that they don't appear to threaten workers' jobs. "They aren't widespread because they don't work," said Jim Lowthers, president of the local 400 of the United Food and Commercial Workers union.

But Lowthers is no skeptic. It's only a matter of time, he said, before retailers develop faster and better systems. Harris Teeter already has added several features to its self-checkout system, including one that checks the accuracy of the scanning by weighing merchandise in customers' bags. Harris Teeter declined to say how much the scanning equipment costs.

"They're working on it," Lowthers said. "I am worried about it. We always worry about anything that could displace people. But the fact of the matter is, you can't stop technology."