For example, "Waiting time at intersection" and "Number of cars at
peak period" are traditional measures of the traffic flow that are
very counter productive to sustainability. Although they are measures
of the "carrying capacity" of a particular road, they are not good
measures of the overall "carrying capacity" of the entire community.
A number of studies have shown that widening roads generally results
in increasing amounts of traffic, which, in turn, requires even wider
roads. There is a limit to the amount of land in a community that can
be devoted to transportation and neither of these indicators addresses
those limits. Nor do these two measures link transportation to other
aspects of the community.
In contrast, "Time devoted to non-recreational travel" links
transportation to work and to free time. In effect, this measures a
piece of a person's social carrying capacity--the amount of time
available in a day--by indicating how a person is able to use that time. Time
spent commuting results in less time for family, friends, community, and
"Portion of household expenses spent on transportation" links
transportation to personal income and therefore to the number of hours
needed to support basic needs. As with time spent commuting, the larger
the percentage of household income used to pay for transportation, the
smaller the percentage of income available for other basic needs.
"Percent of vehicles powered by renewable energy" links transportation
to energy use and speaks to the type of energy used.
"Ability of non-drivers to reach employment centers" links
transportation to work as well as to social equity and housing.
(If there is time, ask the participants for additional ideas of better