Walking is another beneficial utilization of human energy. Although not necessarily the most time efficient method of transportation, the benefits of walking still outweigh the time consuming nature of the activity. Commuting by foot is beneficial, because it reduces the commuters’ carbon footprint while simultaneously helping reduce airborne smog (Howard). Because walking releases no emissions into the atmosphere aside from our respirations, commuters eliminate a large portion of pollutants which automobiles release into the atmosphere and also reduce Americas’ CO2 emissions. Walking also has immediate benefits on our environment. Because commuting on foot does not require specialized and large pathways, i.e. roads, walking protects the living environment as well as natural resources (Bilzon). By utilizing the body as a transport source, the necessity for tarring roads becomes minimal, thus reducing the need for tar, one of the major by-products of oil, which will help the US to conserve natural resources. Also, by not paving new roads, the natural environment is protected, leaving more plants and trees, which means more CO2 to O2 conversions through photosynthesis and respiration, which is beneficial to earth’s atmosphere. This extra foliage will filter the pollutants produced by automobiles and other polluting sources. The majority of the pollutants released by automobiles occur during the cold start phase, where the car or truck has just been started. When commuters walk instead of drive, they eliminate the pollutants released from a cold start vehicle (Bilzon). As with bike riding, substituting walking for automobile use reduces roadway congestion, while simultaneously eliminating harmful atmospheric emissions, while still remaining feasible and cost-effective for many situations. New technology is also being developed to further increase the benefits of walking for the environment. One company in particular, Pavegen, has developed rubber paving slabs which can replace the concrete slabs currently in use. However, these new paving slabs are not just for show; every time a commuter steps, the Pavegen slab compresses slightly, and converts the kinetic energy from the compression into electricity which is readily usable (Pavegen Systems). By walking through areas with Pavegen slabs, commuters not only eliminate the pollutants produced by automobiles, but also reduce the need for coal to produce electricity, as the power created by the Pavegen system supplements electrical company contribution. The Pavegen system is one of many technologies which should be utilized when constructing new areas of sidewalk, and should be used when it comes time to replace old sidewalk sections. Walking remains the cheapest mode of transportation, as there is really nothing necessary to participate aside from the commodities, such as clothes and shoes, which Americans use every day. Thus, commuting by foot is an indispensible part of America’s investment into alternate transportation, and while not feasible for every situation, should be utilized whenever possible.