NEW YORK (CNN/Money) - Can The Revenge of the Mummy, Halfpipe and The Twilight Zone Tower of Terror bring guests back to the nation's theme parks?

With business picking up, theme park operators hope scary new rides will lure big crowds.

Or will it take a lower dollar and a shift in demographics?

Some experts say the theme-park industry, which is still recovering from a post-Sept. 11 downturn, may need more than a few heart-pounding attractions to fuel growth going forward. The summer season, which generally begins around Memorial Day, accounts for the bulk of its $10.5 billion in revenue.

"We're not looking for a major growth spurt," said Arthur Gruen, partner at the New York-based entertainment & media consultant Wilkofsky Gruen Associates. "We think it (the theme-park industry) will grow about 4 percent in terms of total revenue, while attendance will edge up fractionally by 1 to 2 percent."

"There doesn't appear to be a dramatic thrust that would drive traffic higher," Gruen said. "One thing that does drive attendance is a major new park. There were none in 2003."

As with other aspects of the economy, currency fluctuations and fuel prices are likely to have an impact -- although in different directions.

"If the dollar stays weak, that's a boost to tourist attendance especially at the destination parks," said Gruen, since tourists from outside the United States are more likely to exchange their stronger currency here.

"But one wild card this season is the high gasoline prices which could hurt the regional parks whose business depends largely on folks who live two to three hours away," he added.

Another concern for the industry, Gruen says, is that theme park-goers have gotten older.

Six Flags Halfpipe ride opens this month at the Elitch Gardens park in the Denver area.

"Today, families are bringing their parents or even their grandparents with them to amusement parks," he said. "That's one reason why there's been a shift in focus. Many theme-park operators are adding fewer new rides and instead finding ways to become more family-friendly destinations."

For example, Cedar Fair LP (FUN: Research, Estimates) spent about $22 million to convert an existing hotel at its flagship Cedar Point park in Ohio into an indoor water park resort called Castaway Bay that is set to open this November.

"In terms of our capital expenditure, the focus is on the family resort side of our business rather than on the high-glamour thrill side," said Brian Witherow, a spokesman for Cedar Fair, said.

But whenever a new theme park season begins, families search out the new thrill rides that parks have spent the off-season constructing.

"Innovative rides are still crucial to this industry to draw in the crowds, even though there don't appear to be as many new ones as in the past," said Gruen.

Among the highlights:

• Revenge of the Mummy at Universal Studios parks in Florida and California.

"Stephen Sommers, who directed both the Mummy movies and 'Van Helsing,' was our creative consultant. We wanted to give people a truly authentic experience," said Michael McLane, spokesman for Universal Parks & Resorts, a unit of General Electric (GE: Research, Estimates)'s NBC Universal.

• Halfpipe at Six Flags Inc (PKS: Research, Estimates).'s Six Flags Elitch Gardens in the Denver area.

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The ride, along with 3-D animations based on "Spongebob Squarepants" and the "Stargate" TV series, are part of a $100 million investment this year by Six Flags, the No. 2 regional park operator behind Walt Disney, spokeswoman Debbie Nauser said. She said the company last year drew about 37 million visitors to its 44 parks in the United States, slightly less than the year before.

• Silver Bullet at Cedar Fair (FUN: Research, Estimates)'s year-round Knott's Berry Farm Park in southern California that debuts in December.
• The Twilight Zone Tower of Terror at Disney's California Adventure, based on the "a lost episode" of the classic "Twilight Zone" television series. The company has had a similar attraction at Walt Disney World in Florida for several years.

Parent company Walt Disney (DIS: Research, Estimates) reported better-than-expected quarterly results Wednesday, citing among other factors continued improvement in theme park attendance.