NEW YORK (CNN/Money) - This summer's travel season is expected to be the busiest in years, but with warnings of a possible terror attack inside the United States, security concerns will also be high.

334 million people will travel the nation's roads, rails and skies this summer according to the Travel Industry of America. That's 23 million more than the summer of 2001.

But have security improvements at the nation's ports, airlines, rails and borders kept up with the travel plans?

James Carafano, Senior Research Fellow, Defense and Homeland Security at the Heritage Foundation says compared to 2001 the federal government is doing better, but certainly can do more.

"I don't think 9/11 could happen today between the Air Marshal program, the hardening of cockpit doors, the added emphasis on the screening of passengers and intelligence that's been focused on that kind of threat. I think there has been good progress in airline security," he says.

But securing the more than 5,000 mile-long Canadian border and the 2,000 mile-long Mexican border have proved to be bigger challenges.

Commissioner Robert C. Bonner of U.S. Customs and Border Protection says, "The terrorist attacks of 9/11 have brought about profound changes in our nation, none of which is more important than the creation of one single border agency, U. S. Customs and Border Protection (CBP), which has the responsibility of securing the borders and the land, sea, and air ports."

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"This one agency in the Department of Homeland Security has made tremendous strides through technology and efficient use of its trained work force to safeguard the border. There is still much to be done but there are 42,000 dedicated men and women in a single agency working together to accomplish it."

America's 95,000 miles of coastline and 361 ports present another security hurdle. Every year, nine million sea containers enter the United States via our seaports.

Dr. Larry Howard, Assistant Professor at the California Maritime Academy, says there is heightened awareness and there have been some improvements at U.S. ports, but not enough.

"It is a huge vulnerability and right now we have taken a few steps forward but everyone's crying about where we're going to get the money to put security in place and focusing on technology. What they should really be focusing on is changing their way of thinking -- to think about what our vulnerabilities are."  

Join us all this week for our series of special reports, "Homeland Insecurity: How Safe Are We?" Each night we look at a different security challenge facing the United States.