Civil Engineering Reference
In-Depth Information
Fig. 11.1 Elements of
accessibility
Hanson and Giuliano in their topic
The Geography of Urban Transportation,
[
1
]
note that
“
urban planners and scholars have long argued that accessibility should be
a central part of any measure of the quality of life. In contrast, the goal of trans-
portation planners (and traffic engineers) has been to increase people mobility,
sometimes equating increased mobility with increased accessibility.
This evokes
the need to recognize that transportation and land use are interconnected elements
of the urban system that impact on accessibility.
This interconnection is a function of the
location
of activities (close together or
far apart) and the
directness
of travel to reach them. Road networks that are
designed to serve travel by private motor vehicles are based on a hierarchical
classi
”
cation system of road types that guide a typical trip from local roads to
collector roads and from collector roads to higher capacity/higher speed arterial
roads
including freeways. This type of hierarchy favors auto mobility for
long
trips
but it penalizes mobility by alternative modes for short trips because it reduces
the number of direct path choices needed to encourage walking and biking. For
example, as shown in Fig.
11.2
[
2
] traveling between points A and B involves a
longer distance (3.6 miles) with a hierarchical network, but a much shorter distance
(1.3 miles) with a strongly interconnected network.
The distance (1.3 miles) between A and B could easily be traveled by biking on
local streets but the same trip made on a hierarchical network with numerous
disconnected dead end streets connecting to high speed arterials in a circuitous
manner, is considerably longer (3.6 miles). This condition is less conducive to
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