The study evaluates the prices of travel between October 2013 and January 2014 on various modes of transportation — air, bus and rail — in 52 popular city pairs with travel distances between 100 and 500 miles under various advance purchase scenarios. The results show that the differences in fares between modes are significant and larger than is commonly believed.

"The savings from bus travel proved remarkably robust, regardless of whether a consumer books in advance or waits until just a day before departure to buy a ticket," said Joseph P. Schwieterman, professor, School of Public Service and Director of Chaddick Institute for Metropolitan Development at DePaul University. "This ticketing flexibility adds greatly to the popularity of bus travel."

As an example, in the New York to Pittsburgh city pair, the average fare was $51.30 for megabus.com, with a seven-day advance purchase. Under the same date/parameters, air travel was considerably more expensive at $182.50 and $186.78 on Southwest.com and Orbitz.com, respectively.

Highlights of the study include:

• City-to-city bus companies, including megabus.com, have dramatically expanded in recent years and have added service at a rate far faster than any other transportation mode.

• Customers save at least $31 on one-way trips compared to train travel and $169 per trip compared to air travel.

• Travelers in the Northeast enjoy the largest savings when switching from trains to buses. A traveler booking a week ahead saves an average of $67 per one way trip.

• Travelers in the Pacific enjoy the largest savings when switching from air travel to buses. A traveler booking four weeks ahead saves an average of $142 one way.

• One-way price difference between bus and air travel can exceed $250 each way.

• Even air travelers booking their trips four weeks in advance to obtain the lowest airfares save nearly $200 roundtrip by taking the bus.

• Bus customers who purchase tickets one day before departure save an average of more than $300 roundtrip over what they would spend for airline tickets booked a week in advance.

• In all regions of the country, motor coach travel is substantially less expensive than single-occupant driving, even for motorists who consider only the cost of fuel and tolls and ignore depreciation.

To view the study, click here.