Deciding where to vacation is always a balancing act: money vs. time, the kids' desires vs. your own, whether to travel far or near. Adding environmental considerations might actually make the choices easier -- and do the planet some good at the same time. Discover how your travel choices can make a difference:

(Hate quizzes? Skip straight to the answers.)

1. A Los Angeles resident is planning a vacation to Seattle. Which way to get there and back generates the least amount of global-warming carbon dioxide?
   Booking a round-trip seat on a commercial flight.
   Making the roughly 2,000-mile roundtrip in a 15-miles-to-the-gallon SUV.
   

2. Consider the same vacation, but this time for a family of four and a third travel choice. Which generates the least CO2?
   Catching a commercial flight.
   Making the trip in the 15-mpg SUV.
   Making the trip in a 30-mpg car.
   

3. Does it really matter whether I take a plane or train or drive? That plane's going to fly even if I'm not on it.
   Yes
   No
   

4. While jet fuel and vehicle gasoline both generate about the same amount of CO2 per gallon burned, the mile-for-mile effect of jets is more than twice that of autos and trucks.
   True
   False
   

5. When you do fly, it's easier on the environment if you take non-stop flights.
   True
   False
   

6. Given the role gas mileage plays into the drive-or-fly decision, would it be better to take the smaller car instead of the van or SUV?
   Yes
   No
   

7. How do passenger trains stack up against commercial airlines?
   Per passenger-mile, trains use about a fifth less energy than planes.
   Amtrak's trains run on diesel fuel, the manufacture of which requires less crude oil than jet fuel, gallon-for-gallon.
   Since trains run on the ground, they avoid the cloud-producing issues of high-altitude commercial flights.
   All of the above.
   

8. When one must fly, does it help to buy so-called carbon offsets?
   Yes
   No
   

9. How do commercial airplanes, trains, and cars rank from most to least efficient per passenger mile?
   Cars are the most efficient, followed by trains, then airplanes.
   Trains are the most efficient, followed by cars, and then planes.
   Airplanes are the most efficient, followed by trains, and then cars.
   

10. Are ship cruises a more environmentally friendly way to travel?
    Yes
    No