OK, so how would you even start to figure it out?

Here's a cool calculator that will show you how far your car can travel on a gallon of gas. I put in a bunch of different makes/models of cars, of different ages. For the sake of easy math, I'm going to say, on average, a car can go 20 miles on a gallon of gas. (Yes, I'm sure your car does better. And this is, after all, a guesstimate.)

According to Twin Cities gas prices, a gallon of gasoline today will run you about $2.20.

So $2.20/gal divided by 20 mpg = $0.11/mile (or $0.07/km).

When I carry passengers on my bike, I can go a maximum speed of maybe 15 miles an hour, but I'm much slower on hills, maybe 7 miles an hour, and I probably average somewhere around 11 miles an hour. But I'm carrying two kids, not two adults, so I should pick a number at the low end of that range. And, of course, a pedicab is not always moving. So for the sake of easy math, I'll just say an average of maybe 5 miles per hour. Assume an 8-hour working day, and that gives you 5 mph x 8 hrs/day, for a total of 40 miles per day.

Calculating fuel for the cyclist is the tricky bit. The CIA's World Factbook estimates the US per capita GDP at $48,000. That works out to $132/day. And this 2006 Forbes article says Americans spend about 13% of their income on food. So we spend maybe $17/day on food.

$17.00/day divided by 40 miles/day = $0.42/mi or $0.27/km.

The car uses more energy per mile, but gasoline is a cheaper fuel than food. However, the fuel costs for the car depend on the distance traveled. If you double the distance traveled by car, you double the fuel cost. With a pedicab, the fuel cost is the same, per day, no matter how far you go.

And, of course, you're probably eating today whether or not you're pedaling a rickshaw. So get out there and ride! Don't let that fuel go to waste!