I thought of this idea where society would move away from cars and roads and move to a different mode of transportation...zip-lines. The objective behind this fun and adventurous way of traveling is that it would be completely energy free. People would effectively travel around the city without burning fossil fuels by simply clipping on to a rope and using gravity to send them places. The idea is not to cloud the skies with ropes for shorter distances like from your house to school, but more of a larger public form of transport, similar to a subway or an interstate highway like I-35, in which the zip-line would take you from Austin to San Marcos and second to take you back. The only problem is that you would still have to drive to thezip-line station or even better ride your bike there. If this idea is organized correctly across the entire United States, zip-lines will save billions of dollars, and could be an intercity transport as well. First, the zip-lines will be the perfect form of transportation for many people, making cars for them unnecessary (it may reduce cars to 1 per household rather then 4 cars per household like my family). With the reduction in demand for cars, the amount of cars constructed would go down which would save billions of dollars on energy, materials, and labor. Also CO2 and other pollution emissions would decrease with the decrease in cars driven and highways constructed. Not only that, but less of the environment would be destroyed due to roads and highways. Part of the joy of zip-lines is flying over the beautiful greenery, which would be conserved due to the zip-lines.  An argument that can be constructed againstzip-lines is that it takes jobs and valuable income away from our nation, and simply that it just doesn’t seem to be a good idea for mass transportation. As far as the practicality of this mode of transportation is concerned, I feel that anything’s possible as long as it is implemented intelligently. This could become the most practical form of transportation but we could never know unless we try it.