Civil Engineering Reference
In-Depth Information
several neighborhoods) [
2
]. Overcrowded living conditions became a major social
and environmental concern in New York City.
The appearance of streetcars, subways, elevated rail, and commuter rail lines,
with their higher operating speeds, replaced the horse drawn cars by extending the
distance that people could travel within acceptable travel times. This technological
development reduced population densities and increased employment densities in
city centers and it transformed the urban landscape by enabling settlements to
expand into new territories previously inaccessible by the slower modes of
transportation.
New rail transit lines were laid out to connect the population to jobs and
shopping locations in the central business district (CBD)
—
which became the most
accessible place in the city.
The steam railroads that appeared in the latter half of the 19th century improved
access between cities. Over the years, many small communities that had access to
train stations, became suburbs of nearby cities.
The commuter railroad operating at higher speeds (30
35 mph), enabled com-
muters to work in the city and live farther out from the city limits (away from the
dirty air) where living space was more affordable, and the environment more
desirable for raising a family. With an average commuter rail speed of 30 mph, one
could cover a door-to-door distance of approximately 12 miles in 45 min.
1
This rail-
based urban expansion, created new towns and villages whose residential and other
land use activities were located within walking distance of the transit stations.
The rail lines allowed (1) increased employment concentration in city centers,
and (2) fostered residential developments in outlying areas.
-
2.2.3 The Private Motor Vehicle Era (1925
-
Present)
With the coming of the motor vehicle, the land between rail lines and beyond
became accessible for development and the distance between land use activities was
no longer limited by the rail lines and the walking distance to their stops or stations.
The technology of the automobile provides people with access to one almost
total freedom to travel
when
and where they want. Its use is not constrained by
service routes or schedules. It offers reliable door-to-door transportation without the
need to change travel modes. It operates at high door-to-door travel speeds relative
to most urban travel modes. It ensures seating and privacy as well as weather
protection. And, last but not least, it offers pride of ownership.
Its higher operating speed (up to 30
40 mph) makes possible traveling longer
distances within acceptable commuting times. Consider a 45 min trip from home to
a job location: if the trip is by car one can reach a job located 30 miles away; if the
-
1
(45 min)
−
(20 min spent to reach vehicle, wait, and reach destination) = 25 min riding time;
25 min/(60 min/hr)
×
(30 mph) = 12.5 miles.
