The continued growth of discount services like BoltBus and Megabus pushed intercity bus travel up 7.5 percent last year, making it the nation's fastest growing intercity transportation segment. By comparison, passenger rail service was up 3.5 percent, car and air travel up only 1 percent.

A U.S. bus-transportation boom that began seven years ago is accelerating as travelers ditch their cars and avoid airport security lines to buy cheap tickets on Wi-Fi equipped motorcoaches.

No doubt the improved amenities and lower prices of these discount bus lines are major draws, but don't underestimate how much the increasingly-crappy air travel experience drives travelers to seek alternatives. Between the hassle, inconvenience and indignities of TSA, the nickel-and-diming of consumers via baggage/seat/food fees, and the generally awful customer service that has become the industry norm, air travel has grown ever more stressful, uncomfortable, and expensive over the past decade or so.

And it's not just intercity bus travel that's picking up the slack. Amtrak served over 31.2 million passengers in 2012, it's ninth ridership record in ten years:

(In case you're wondering, ridership on the Amtrak Cascade line was down 0.8 percent from 2011—I'm guessing those frequent mudslide outages don't help.)

Of course, I can hear those Republican gears churning right now: "Why subsidize Amtrak," they might ask, "when these private sector bus lines can provide comparable service for less?" Well, first of all, the bulk of Amtrak's ridership occurs on the profitable Northeast Corridor; most of Amtrak's subsidy goes toward money-losing, congressionally mandated long distance lines. But second, these buses can only afford to offer such cheap service because they are driving on taxpayer subsidized roads and highways:

“In the past four years, the federal government has appropriated $53.3 billion from the general fund of the Treasury to bail out the Highway Trust Fund,” [Amtrak CEO Joe] Boardman told the committee. “That’s almost 30 percent more than the total federal expenditure on Amtrak since 1971.”

Considering that about 20 percent of the Highway Trust Fund goes to transit, that’s still more for highways alone over the past four years than Amtrak has ever gotten.

And that's just federal dollars. Every penny the state spends paving I-5 helps pave the way for BoltBus's Vancouver-Bellingham-Seattle-Portland service. But then, every mode of transportation, public or private, benefits from government subsidies in one form or another, so it's kinda silly to point fingers.

Defenders of our automobile culture like to equate cars with freedom, and yet when given the freedom to choose between various transportation alternatives, more and more American travelers are choosing buses and trains. Go figure.