Transportation's Role in Reducing U.S. Greenhouse Gas Emissions ...

Transportation’s Role in Reducing U.S. Greenhouse Gas Emissions: Volume 2
American adults are now overweight and nearly one in three is obese (Flegal et al., 2002).
Many researchers believe that the design of most communities in the latter half of the 20 th
century has contributed to environments that are unsafe and inconvenient for walking and
bicycling, thereby influencing decisions not to adopt those behaviors for transportation or
recreation (Cambridge Systematics and Killingsworth, 2006). The evidence from many
studies on walking and bicycling demonstrate that regular participation in these activities
provides a health benefit for people of all ages, genders, and races (Dunn et al., 1999).
Bicycle and pedestrian strategies can improve mobility by providing people with increased
travel options, at a lower cost. Bicycle and pedestrian improvements and programs should
also increase safety for nonmotorized travelers. At more aggressive levels, however, some
bicycle and pedestrian strategies may require compromises in vehicle operating conditions
and therefore vehicular mobility, e.g., reduced traffic capacity if general purpose lanes are
reduced to create bike facilities, or traffic calming in business districts which slows
vehicular movement.
Feasibility
Pedestrian improvements have proven to be popular in many cities, and the benefit of
pedestrian-supportive design is gaining fairly wide acceptance. Widespread
implementation of such improvements, however, can be a challenge for financially
strapped municipalities. The extent to which walk trips can reduce VMT and GHG is
primarily driven by the arrangement of land uses, and in particular, having dense, mixeduse
environments where people can walk to destinations or to transit.
Bicycle improvements are also gaining in popularity, but still face political, institutional,
and technical challenges especially when compromises are required with traditional
roadway designs oriented towards motor vehicles. The ability to implement bicycle
facilities—whether on-street or off-street—is also often limited by physical constraints on
right-of-way availability. The extent to which people will be willing to bicycle for
transportation is limited by practical constraints (e.g., need to carry packages, transport
children, travel long distances, weather issues) as well as cultural factors, although some
European countries have managed to make bicycling a widely acceptable mode of
transport.
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