There have been many efforts to plan towns and transportation systems to accommodate walking, bicycling, small vehicles, and other modes that can mitigate the impacts of automobile use. The approach taken here, however, is novel in that it completely separates high-speed, high-mass vehicles from low-speed, low-mass vehicles on a city-wide scale. Thus, instead of having a single road system that serves everything from 25-kg children walking at 3 km/h to 70,000-kg trucks traveling at 100 km/h, this new design creates towns with two separate road systems, segregated according to the mass and speed. Cut-off points of 40 km/h top speed1 and 500 kg maximum curb weight distinguish low-speed, lightweight modes (LLMs) from fast, heavy vehicles (FHVs). LLMs include any mode of transport under these limits (e.g., pedestrians, bicycles, pedicabs, mopeds, motor scooters, motorcycles, golf cars, minicars). FHVs include conventional cars, trucks, and vans driven daily as well as tractor-trailers which deliver most consumer goods. The physical infrastructure of the LLM network ranges from an undifferentiated narrow lane that handles
1 Note that the maximum speed limit is a design or technology limit, not an enforcement option: the LLMs are to be constructed so that they are incapable of exceeding the maximum allowable limit. This requirement already has been implemented in the U.S. in the recent regulations governing the safety and speed of "low-speed vehicles" (Federal Register 1998).
all LLMs (where traffic volumes are very low) to a multi-lane roadbed for motorized traffic, with a paved bicycle path and an unimproved pedestrian path on the side (where traffic volumes are high). FHV roads will be similar to present conventional roads.
This approach is distinctive at several levels: It accepts that many people may wish to live in single-family homes, in relatively low density, and get around mainly in automobiles (LLMs or other vehicles). Thus, the town is designed to accommodate these preferences. At the same time, it offers qualitative improvements in, for example, safety, aesthetics, travel pleasure, infrastructure cost, social organization, and pedestrian space. To accomplish this, travel is separated according to kinetic energy of modes. Finally, the proposal delineates a land use and transportation infrastructure layout that enhances ef-fi ciency and community, while minimizing energy use, water pollution, and nonrenewable resource consumption.
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