Last month, bulldozers broke ground on Washington's latest shopping mecca, Arundel Mills, a sister megamall to Northern Virginia's Potomac Mills. The shopping and entertainment complex will feature a bevy of national chain stores and a 24-screen multiplex movie theater, along with attractions such as a skateboard park, and possibly a sporting goods store outfitted with an indoor fishing stream.

The giant retail outlet destination in northwestern Anne Arundel County near Baltimore also may feature something else: traffic jams.

A study commissioned by the developer, the Mills Corp. of Arlington, indicates that the opening of Arundel Mills 15 months from now in November 2000 is likely to worsen rush-hour congestion on the Baltimore-Washington Parkway near Route 100--particularly in the late afternoon.

And partial relief, in the form of new lanes on the parkway and a new interchange, is not expected until at least six months after the mall opens.

Dennis Connolly, the Mills Corp. vice president in charge of the Arundel Mills project, says the company is committed to doing what it takes to accommodate whatever traffic the mall generates.

"We live and die by how people get there. It's in our best interests to make sure people can get to the mall and leave without problems," he said.

Mills Corp. malls across the country have proven themselves to be such popular destinations that some congestion is inevitable. CEO Larry Siegel hopes Arundel Mills and Potomac Mills become the retail "bookends" of the Washington metropolitan market. Potomac Mills, located 30 miles south of Washington in Prince William County, has evolved into Virginia's No. 1 tourist attraction since it opened in 1985.

Congestion due to Potomac Mills has not been as heavy as traffic that has clogged roads near a few of the company's other properties. It operates eight large malls across the country, with two more scheduled to open this fall.

In Tempe, Ariz., a newspaper report on the first anniversary of the Arizona Mills last year described the mall as a "Traffic Monster."

In suburban Chicago, the fourth-most accident-prone intersection in the state of Illinois is located outside the Gurnee Mills megamall, according to the state department of transportation.

In Southern California, the opening of Ontario Mills in 1996 transformed the local interstate into what one business newspaper described as "a virtual parking lot."

To avoid similar problems in Anne Arundel County, state and county traffic engineers in Maryland are laying out plans to expand the capacity of the parkway and of local roads in the vicinity of Arundel Mills.

Nonetheless, Neal Pedersen, director of planning for the Maryland State Highway Administration, anticipates the improvements will not prevent all future traffic problems.

"On the mainline of the parkway, north and south of the Mills project, we are expecting congested conditions" in coming years, Pedersen said in an interview.

A traffic study conducted by Wells & Associates, a Fairfax-based traffic consultant hired by the Mills Corp., suggests that the biggest problems are going to come in the evening rush hour.

Using accepted formulas for how retail stores generate shopping trips, Wells estimated that Arundel Mills will generate a total of 2,630 vehicle trips during the peak hour of traffic between 4 and 6 p.m.

About half of those vehicles will travel on Route 100, which runs just north of the Arundel Mills site, and Interstate 95, which sits five miles to the west of the megamall, according to Terry Miller, vice president of Wells & Associates.

The rest of the mall traffic will travel primarily on the parkway, he says. The firm's computer model predicts about 600 vehicles will travel north and another 600 south.

That would add enough cars to qualify that stretch of the parkway for a traffic engineer's grade of F. Under such conditions, the flow of vehicles breaks down, stop-and-go traffic results, and the average travel speed declines to less than 30 miles per hour, according to the Highway Capacity Manual, a reference book for traffic engineers.

Miller says the congestion may not turn out to be quite so bad because some of the people likely to travel to and from the mall are already using the parkway and thus may be counted twice in the computer model.

Pedersen also cautioned against attributing future parkway congestion solely to the mall. Parkway traffic has been increasing 3 to 4 percent per year in the 1990s without any mall, he notes.

Congestion, he said, "will either happen at the mall or at some other development in the area."

In response to such projections, the state has approved a plan for the Mills Corp. to build at its own cost an interchange on the parkway between the Route 100 and Route 175 exits. The entrance and exit ramps will feed cars and trucks directly into the mall.

The new interchange will become operational in May 2001, according to the Mills Corp., six months after the mall is scheduled to open. The Mills Corp. and the highway administration also plan to expand the parkway from two lanes to three in each direction between Routes 100 and 175--again at company expense.

There is no set date for completion of the lane expansion. Cost estimates were unavailable.

Miller said that the traffic problems at other Mills malls are not relevant to the Arundel project. "Our problem in Arizona is that access to the mall comes off of a left turn," he said. "Those are always harder to manage. At Arundel Mills, we've got all right turns."

The problems at Gurnee Mills, he said, were due to massive unplanned residential developments to the west of the mall.

In Ontario, he said, an infusion of federal dollars to fix a problem interchange near Ontario Mills is going to alleviate the traffic problems there.

Bob Tyson, the traffic engineer for Anne Arundel County who is still reviewing the Mills Corp.'s designs for 11 new or expanded intersections in the vicinity of the mall, said: "I think they're learning from their past mistakes."

CAPTION: Arundel Mills (This graphic was not available)

CAPTION: Construction has begun on the new Arundel Mills mall. The mall is to open in November 2000, but new lanes and a new interchange will come later.