Civil Engineering Reference
In-Depth Information
Example 1
Land Use Density Assumptions
: average number of destination opportunities per
square mile located within the travel opportunity area (e.g., number of stores selling
shoes per square mile)
A. High-density center city
—
where walking, biking, and bus transit is provided = 5
shoe stores/square mile
B. In the suburbs where car access is used = 0.1 shoe stores/square mile
The number of shoe buying opportunities accessible within 30 min travel time:
A. Center City
walking = 5 stores/square miles
×
5 square miles = 25 stores
biking = 5 stores/square miles
×
50 = 250 stores
bus = 5 stores/square miles
×
7 square miles = 35 stores
B. Suburban Area
car = 0.1 stores/square miles
×
572 square miles = 57 stores
Key points:
Using the same travel time budget, slower modes in the city can provide higher
accessibility to destination opportunities than can faster modes in the suburbs.
Traveling in cities for business, for personal needs, or shopping, is usually
different than traveling for the same purpose in suburban areas. Cities are more
crowded with people (residents and visitors who often walk to reach their desti-
nations), road traf
c moves slowly, and bus transit speeds are even slower. Thus
travel mobility in cities is considerably less than in the suburbs but, the same cannot
be said about access to urban activities. In cities, where land use densities are 10
15
times those found in suburban areas, the number of destination opportunities one
can
-
15 times the
number found in suburban areas. This simple example illustrates that one should
only just focus on mobility in the analysis of a transportation system performance,
without considering access to activities.
find within a 20 min trip
—
walking, driving, or by transit
—
are 10
-
Example 2
From empirical data of urban travel behavior, it has been observed that travelers
tend to keep their trips as short as possible (see example in Fig.
11.5
).
This means that destination opportunities closer to the traveler are likely to be
selected more frequently than those located far away.
The number of activity sites and the size of their activity (employment locations,
retail and service outlets, and recreational opportunities) that can be reached at a
