How can transportation be sustainable?
While many common modes of transportation are, in fact, sustainable -- walking, biking, rollerblading... there are an awful lot of modes which are not -- gas-guzzling SUVs, travel by plane, cruise ships. Modern life often necessitates travel by largely unsustainable methods. Most people needing to make a trip for business, for instance, don't have the option of walking or bicycling to their destination. Often, one's job requires traveling some distance to work, and frequently there are no alternative transportation options, the worker must get on the freeway with millions of others making their way to work for a maddening jockeying for position between those who drive as if their lives depended on getting to work on time, and those who drive as if they've somehow mistaken the morning rushhour for their Sunday afternoon drive through the country (another unsustainable practice, by the way).
If one lives in a reasonably large city, alternatives are easier to come by; Busses and trains can haul commuters to their destinations.
There are other options, though. Hybrids are decreasing the need for oil, but only by decreasing the amount needed. They aren't the answer, but they are a step in the right direction. Bio-diesel seems promising, especially in today's fast-food world (also unsustainable, but we'll talk more about that in the Food section). Electric cars might be the perfect solution - provided travel needs are limited to within 30 miles of home and the electricity generated to charge the car were produced by wholly renewable resources - sun, wind or water (however, dams which destroy entire eco-systems would not be part of the water-as-a-source equation).
Why is my transportation choice important? Mainly, our choices regarding how we get from Point A to Point B are important because we can either contribute to pollution (emission), the destruction of natural environments (extracting and transporting oil), and reliance on foreign sources of energy or not. This is what we need to consider when deciding on a method of transport.