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(a) The fuel cycle includes the life cycle of fuels, from feedstock production to end use, and emissions related to vehicle maintenance, repair, and servicing. The fuel+material life cycle includes the life cycle of fuels plus the life cycle of all materials, vehicle assembly, and infrastructure construction.

(b) The average occupancy of buses in the U.S. is around 10, and average capacity factor for trains is around 20% (see statistics reported by the Federal Transit Administration). Emissions per passenger km are shown at both the current average occupancy and double the current average.

(c) The average power mix in the U.S. in the year 2010 is estimated to be 50% coal, 1% fuel oil, 25% natural gas, 14% nuclear, 8% hydro, and 2% biomass.

(a) The fuel cycle includes the life cycle of fuels, from feedstock production to end use, and emissions related to vehicle maintenance, repair, and servicing. The fuel+material life cycle includes the life cycle of fuels plus the life cycle of all materials, vehicle assembly, and infrastructure construction.

(b) The average occupancy of buses in the U.S. is around 10, and average capacity factor for trains is around 20% (see statistics reported by the Federal Transit Administration). Emissions per passenger km are shown at both the current average occupancy and double the current average.

(c) The average power mix in the U.S. in the year 2010 is estimated to be 50% coal, 1% fuel oil, 25% natural gas, 14% nuclear, 8% hydro, and 2% biomass.

The results reported in Table 24.1 show that LLMs will provide large reductions in life cycle emissions of greenhouse gases, even when compared with relatively efficient subcompact gasoline FHVs (e.g., 8.4 l/100 km in city driving). Full-feature electric LLMs, which are anticipated to comprise most of the traffic on the LLM network, offer emissions reductions of around 80% compared with FHVs. They offer lower emissions than public transit, except as compared with rail transit that has double the current average load factor in the U.S. And of course the smaller LLMs, such as scooters and bicycles, offer greater reductions in emissions than even high-occupancy public transit.

Because of the close relationship between energy use and greenhouse gas emissions, percentage reductions in energy use are similar to the percentage reductions in emissions shown in Table 24.1. Percentage reductions in oil use are similar for the petroleum-using options and greater for the electric options. LLMs reduce total energy use for transportation, and thus reduce petroleum consumption.

Water Pollution

Oil, fuel, coolant, and other chemicals leak or are discarded from motor vehicles and petrol stations and eventually pollute rivers, lakes, wetlands, and oceans. Impervious surfaces, such as roads, collect the pollutants and transmit them to water bodies during runoff from rain and snow melt. This polluted runoff, in turn, can significantly degrade rivers, lakes, streams, and wetlands, and even threaten human health. Gaffield et al. (2003) note that storm runoff is a major threat to water quality.

LLMs and the LLM infrastructure will greatly reduce problems associated with runoff and water pollution. Consider the LLMs first: If LLMs are either nonmotorized or electric-powered, then compared with FHVs and LLMs powered by internal combustion engines, leaks and discharges of lubricating oil and engine coolant will be greatly reduced, and leaks of fuel (and constituent chemicals, such as the oxygenate methyl tert-butyl ether) from vehicles and underground tanks will be eliminated. Furthermore, to the extent that the use of motor fuel affects the probability of large spills of crude oil in sensitive habitats, the use of nonmotorized or electric LLMs will reduce the frequency and costs of oil spills. Finally, the much lower vehicle mass and speed of LLMs compared with FHVs will also reduce the creation of dust from tires and brakes and hence reduce the concentrations of these pollutants in runoff.

In terms of the LLM infrastructure, because streets intended for LLMs do not need to support wide, heavy, high-speed vehicles, alternate surfaces (e.g., permeable street surfaces) can be used instead of conventional solid pavements with curbs, gutters, and storm drains to control street runoff. Permeable pavements allow water to seep through the surface of the road, so that something akin to natural filtration can occur. This filtration removes water pollutants and replenishes local groundwater, thereby enhancing soil quality and promoting plant growth. In addition, permeable pavements may absorb and store less heat and be less reflective and less prone to cause glare.

Aesthetics

The present motor-vehicle infrastructure is ugly (Button 1993). Roads, gas stations, car sale lots, car repair shops, parts stores, parking lots, and garages form dreary, chaotic strip developments decried by architects and city planners (e.g., Wright and Curtis 2005; Kunstler 1993). Surveys report that the general public feels that the world would be more attractive without roads (Huddart 1978), and that residential streets would be more attractive without large cars (Bayley et al. 2004).

Because of the low speed and small size of LLMs, the LLM network will not have wide roads, traffic lights, medians, railings, or shoulders. In addition, if motorized LLMs use electric motors, the LLM network will not need gasoline stations. All of these features will make the LLM network much less visually intrusive and socially divisive than the present street system. Indeed, properly designed, an LLM network could be an aesthetically pleasing, integral part of a townscape. Even the FHV network in the plan outlined here would be less unsightly than a conventional suburban FHV road system, because houses and businesses are (or should be) oriented away from the FHV road, which function rather like service alleys.

Community Fragmentation

The roads and freeways intended to connect people to places can divide communities, impede nonvehicular circulation, and create barriers to social interaction (Wright and Curtis 2005; Sheller and Urry 2000; Marshall 2000). The conventional FHV infrastructure itself can physically split (or even bury) neighborhoods and vehicle traffic can disrupt the social functioning of neighborhoods and communities.

The LLM network will function to define, unify, and connect neighborhoods rather than to separate and isolate them. No high-speed, high-volume roads transect the neighborhoods. Virtually all roads—FHV as well as LLM— in the system terminate in cul-de-sacs which, when part of a coherent town plan and pedestrian-friendly infrastructure, can help create an "ideal suburban residential environment" (Southworth and Ben-Joseph 2004a).

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