Americans aren't going to let a sluggish economy and an elevated terror alert put an end to their Memorial Day (search) travel plans. People are expected to hit the highways, skyways and railways in droves this weekend. In fact, AAA predicts a record number of people traveling via car, for what is deemed the beginning of summer driving season.

But the travel season didn't start off too smoothly. After being hit by a semi-trailer, a bridge over Nebraska's Interstate 80 (search), the nation's busiest highway and the major east-west corridor through the state, collapsed, causing Midwest travel to be tumultuous. The accident killed the driver and shut down a 10-mile stretch on the interstate.

In Maryland, a 90-car pileup killed two people on Friday, resulting in a 17 mile shutdown of Interstate 68 (search). Fog and rain has hindered cleanup efforts, which prompted officials to acknowledge that the traffic problems will persist throughout the long Memorial Day weekend.

"It's a major interstate going out west, and it's partially closed, with people being diverted, so it's going to be causing problems this weekend," said state police Sgt. David Jones.

An Associated Press poll found that most travelers weren't going to let worries about terrorism and the economy interfere with plans this year. But Americans were more likely to drive to their holiday destinations than before the Sept. 11, 2001, attacks on New York and Washington.

Four of five in the AP poll said problems with the economy and terrorism will have no effect on their vacation plans. Some others said they would postpone or cut back vacation travel, but only one in 20 said they would cancel those plans, according to the poll conducted for the AP by ICR/International Communications Research of Media, Pa.

Meanwhile, scattered showers were expected across much of the country as low pressure systems move across the Southeast and Great Lakes (search).

A lingering system off the Virginia coast was likely to continue triggering showers and isolated thunderstorms over coastal regions of the Southeast and Mid-Atlantic.

None of the storms were expected to be severe, but some strong storms were expected to hit coastal regions of Massachusetts and Maine late in the day. Scattered showers and thunderstorms were seen reaching Florida through the evening.

A low pressure system centered over the Great Lakes Region will produce scattered showers and strong thunderstorms across the Great Lakes, Ohio Valley (search) and Northeast.

Conditions will be calm over most of the West, except for some scattered showers and thunderstorms across Utah, Wyoming, Colorado, and New Mexico. A strong system will push into the Pacific Northwest during the early afternoon, bringing scattered showers and thunderstorms to Washington, Oregon, Idaho, and portions of the Great Basin.

On Interstate 80 in Nebraska, both eastbound and westbound traffic was being rerouted around the Big Springs (search) interchange after the deadly accident, the State Patrol said.

"We're completely packed right now," said Stanley Crandell, assistant manager at the Bosselman Travel Center in Big Springs. "Just a lot of people wanting to know how to get around and keep going to Denver."

Chris Peterson, an aide to Gov. Mike Johanns, initially estimated the interstate would be cleared by Saturday morning, but revised that after officials arrived on scene and saw the damage.

"The bridge fell in such a way that it won't be easily cleared," Peterson said. "It's too early to determine how early the interstate will reopen, the assessment is under way."

Just west of Big Springs is the Interstate 80-Interstate 76 interchange. Interstate 76 is the main route to Denver from Nebraska.

In Finzel, Md., thick fog lingered over Interstate 68 on Saturday morning as crews cleared away the wreckage that left two dead and injured dozens.

A jumble of cars, trucks and tractor-trailers jammed the roadway and shoulders after the pileups began along a fog-shrouded mountain ridge Friday afternoon.

One of the victims was killed after leaving his vehicle to escape the pileup, police said. At least 60 other people were injured.

"The magnitude of vehicles and the damage and devastation was mind-boggling," said Cpl. Rob Moroney, a state police spokesman.

Visibility was near zero atop Big Savage Mountain, an Appalachian ridge in Garrett County where the accidents occurred, county Emergency Director Brad Frantz said.

In the AP poll, 25 percent said they planned in-state vacations, while almost six in 10, 58 percent, said they planned to travel to another state. Fifteen percent said they would travel outside the country.

The number vacationing by car jumped from fewer than half in May 2001 to about six in 10 a year later, after the Sept. 11, 2001, attacks. It remains at that level in this poll.

Just over a fourth, 27 percent, said they would travel by plane, down from a third in 2001.

About half said they would spend the same amount on their vacation this year as they did last year, and the remainder were about evenly split whether they would spend more or less than last year.

The new poll was taken May 14-18 of 1,020 adults and has an error margin of plus or minus 3 percentage points. It was taken before the Bush administration raised the terror alert to high early this week. This is the fourth time the terror alert has been raised to high.

The Associated Press contributed to this report.