Travel Math driving

Last week I borrowed a friend's car and promptly spent $82 to fill the tank. So out of curiosity, I visited the site of the airline industry's low-cost leader, Southwest Airlines, to see how far that same $82 would have taken me. Without even searching very hard, I found the following one-way flights:

• Denver to the West Coast (Los Angeles, San Diego, San Francisco, Seattle, etc.): $79
• Austin to Oakland: $79
• Philadelphia to Florida (Fort Lauderdale, Orlando, Tampa, etc.): $64

Now comparing travel prices on a per-mile basis usually doesn't make much sense. When I worked for the Pan Am Shuttle, the hourly departures between New York and Boston and Washington, D.C., were among the most high-yield flights in the country, so on any given day there were transcontinental fare sales priced for less than those quick hops within the Northeast. But today the price of gasoline has reconfigured the driving vs. flying conundrum in a dramatic way, so the old assumptions about driving being cheaper need to be reevaluated.

There's no question that fuel costs are altering vacation plans this summer. Just this week, the travel site Kayak released results of a survey that found more than 64% of respondents plan to be tourists in their home state or within a three-hour drive of their house. According to Kayak, driving 200 to 400 miles is more affordable than flying.

But what about for longer trips? Last weekend, the AAA reported the national average for unleaded regular fuel was $4.07 per gallon, up from $2.99 a year ago. And even as more gas stations ban charge card sales, the cost of filling up is remaking travel plans for millions of Americans this summer. The bottom line is that gas prices at the pump have skyrocketed across America, rising by about a third over the last year, while airfares have inched upward at a relatively slower pace.

So has the option of flying become the cheaper alternative? The answer is ... sometimes.

Crunching the numbers

Determining how much you'll pay to travel on vacation requires a little bit of time spent with a calculator. In order to crunch your own driving numbers, first you'll need to determine the vehicle's gas mileage. The Environmental Protection Agency's provides miles-per-gallon estimates for both city and highway driving.

As for benchmarking gasoline costs, the best source is the AAA's, which allows you to compare detailed gas prices in hundreds of markets from Akron to Yuma. For a quick and dirty analysis, click on the AAA's, and punch in your origin, destination, and vehicle's year, make, and model to determine mileage, gallons used, and estimated fuel cost. (Be warned, however, that the calculator has occasionally been out of order recently, presumably due to increased demand.)