1) Jane Jacobs advocated for mixed-use development and bottom-up community planning based on local expertise rather than top-down experts. She argued higher density can support vibrant communities if done properly. 2) Jacobs identified four conditions for diversity in cities: districts should serve multiple uses; blocks should be short; buildings should be varied in age and condition; and dense concentrations of people are needed. 3) Forces of decline occur when success leads to overspecialization that drives out diversity, as seen when Jacobs' neighborhood became overrun by similar restaurants. Boundary elements like railways also divide cities.

1. JANE JACOBS THEORY IN
PLANNING
ABAD, COLEEN / BELTRANO, LEAH / EULOGIO, ERNESTO / HABIJAN, KAREN / MAJAN, JEANELYN / RIVERA, FRANCIS / YONGKO, RANDALL

2. IDEAS
•Cities as Ecosystems. Jacobs approached cities as living beings and ecosystems. She suggested that over time, buildings,
streets, and neighborhoods function as dynamic organisms, changing in response to how people interact with them. She
explained how each element of a city - sidewalks, parks, neighborhoods, government, economy - functions together
synergistically, in the same manner as the natural ecosystem. This understanding helps us discern how cities work, how
they break down, and how they could be better structured.
•Mixed-Use Development. Jacobs advocated for "mixed-use" urban development - the integration of different building
types and uses, whether residential or commercial, old or new. According to this idea, cities depend on a diversity of
buildings, residences, businesses, and other non-residential uses, as well as people of different ages using areas at
different times of day, to create community vitality. She saw cities as being "organic, spontaneous, and untidy," and views
the intermingling of city uses and users as crucial to economic and urban development.
•Bottom-Up Community Planning. Jacobs contested the traditional planning approach that relies on the judgment of
outside experts, proposing that local expertise is better suited to guiding community development. She based her writing
on empirical experience and observation, noting how the prescribed government policies for planning and development
are usually inconsistent with real-life functioning.
•The Case for Higher Density. Although orthodox planning theory had blamed high density for crime, filth, and a host of
other problems, Jacobs disproved these assumptions and demonstrated how a high concentration of people is vital for
city life, economic growth, and prosperity. While acknowledging that density alone does not produce healthy
communities, she illustrated through concrete examples how higher densities yield a critical mass of people that is capable
of supporting more vibrant communities. In exposing the difference between high density and overcrowding, Jacobs
dispelled many myths about high concentrations of people.
•Local Economies. By dissecting how cities and their economies emerge and grow, Jacobs cast new light on the nature of
local economies. She contested the assumption that cities are a product of agricultural advancement; that specialized,
highly efficient economies fuel long-term growth; and that large, stable businesses are the best sources of innovation.
Instead, she developed a model of local economic development based on adding new types of work to old, promoting
small businesses, and supporting the creative impulses of urban entrepreneurs.

3. THE PECULIAR NATURE OF CITIES
Jacobs briefly explains influential ideas in
orthodox planning, starting from Howard’s
Garden city, indeed a set of self-sufficient small
towns, ideal for all but those with a plan for
their own lives. Concurrently, City Beautiful was
developed to sort out the monuments from the
rest of the city and assemble them in a unit.
Later Le Corbusier devised the Radiant City,
composed of skyscrapers within a park. Jacobs
argues that all these are irrelevant to how cities
work, and therefore moves on to explain
workings of cities in the first part of the book.
She explores the three primary uses of
sidewalks: safety, contact, and assimilating
children. Street safety is promoted by
pavements clearly marking a public/private
separation, and by spontaneous
protection with the eyes of both pedestrians
and those watching the continual flow of
pedestrians from buildings. To make this eye
protection effective at enhancing safety, there
should be “an unconscious assumption of
general street support” when necessary, or an
element of “trust”.
As the main contact venue, pavements
contribute to building trust among neighbors
over time. Moreover, self-appointed public
characters such as storekeepers enhance the
social structure of sidewalk life by learning the
news at retail and spreading it. Jacobs argues
that such trust cannot be built in artificial public
places such as a game room in a housing
project. Sidewalk contact and safety,
together, prevent segregation and racial
discrimination.

4. THE PECULIAR NATURE OF CITIES
A final function of sidewalks is to
provide a non-matriarchy environment
for children to play. This is not achieved
in the presumably “safe” city parks -
an assumption that Jacobs seriously
challenges due to the lack of
surveillance mechanisms
in parks. Successful, functional parks
are those under intense use by
a diverse set of companies and
residents. Such parks usually possess
four common characteristics: intricacy, c
entering, sun, and enclosure. Intricacy is
the variety of reasons people use parks,
among them centering or the fact that
parks have a place known as
their centers. Sun, shaded in the
summer, should be present in parks, as
well as building to enclose parks.
Jacobs then explores a city neighborhood,
tricky to define for while it is an organ of self-
governance, it is not self-contained.
Three levels of city neighborhoods; city,
districts, and streets, can be identified. Streets
should be able to effectively ask for help
when enormous problems arise.
Effective districts should therefore exist to
represent streets to the city. City is the source
of most public money – from federal or state
coffers.

5. THE CONDITIONS FOR CITY DIVERSITY
Diversity is the concept that Jane Jacobs puts in her work and the central definition of a
city. Jane Jacobs believes that diversity is the key principle for urban success because
mutual economic and social support are the benefits of diversity. She advocated that
there were four principles to create diversity
1) The district must serve more than one primary use, and preferably more than two.
Jane Jacobs believes that “To understand cities, we have to deal outright with
combinations or mixtures of uses, not separate uses, as the essential phenomena.”
Jane Jacobs advocated intermixing or mixture of use and functions of any building
occupancy classification like residences, offices, restaurants, low scale retail, industry
and etc. These might insure the presence of people who go outdoors on different
schedules and people who are in the place for different purposes, but who are able to
use many facilities in common.
2) Most blocks must be short.
This would make promote walking to get to other parts of the neighborhood (and
buildings with other functions), and it would also promote people interacting. This
allows diverse flows of traffic, as well as more locations for businesses.

6. THE CONDITIONS FOR CITY DIVERSITY
3) Buildings must be mingled in their age, condition, and required economic yield.
“Cities need old buildings so badly it is probably impossible for vigorous streets and districts to
grow without them.” -Jane Jacobs, The Death and Life of Great American Cities
Neighborhoods should contain a mixture of older and newer buildings. Older buildings might need
renovation and renewal but should not simply be razed to make room for new buildings, as old
buildings made for a more continuous character of the neighborhood. Her work led to more focus
on historical preservation.
4) A dense concentration of people.
"The district must have a sufficiently dense concentration of people, for whatever purpose they
may be there. This includes people there because of residence."
A sufficiently dense population, she argued, contrary to the conventional wisdom, created safety
and creativity, and also created more opportunities for human interaction. Denser neighborhoods
created "eyes on the street" more than separating and isolating people would.
"All four in combination are necessary to generate city diversity; the absence of any one of the four
frustrates a district's potential." - Jane Jacobs, The Death and Life of Great American Cities

7. FORCES OF DECLINE AND REGENERATION
Forces of Decline and Regeneration,” deals with the cycle of
success and failure, or “slumming and unslumming,” in
American cities.
In the first chapter of this section, Jacobs details the “self-
destruction of diversity” that occurs as a result of a successful
city. Starting in neighborhoods, each city witnesses the success
of certain businesses, and, as investors observe these trends,
money is poured into similar businesses.
The resulting competition drives out the less affluent and smaller
scale business owners and replaces them with more of the same
type of storefront. As a result, not only are some neighborhoods
oversaturated with one or two types of businesses, but also
other neighborhoods are thus deprived of profitable businesses.
The distribution of affluent residents follows a similar pattern,
and the result is clusters of residents with small ranges of
incomes in each neighborhood. Jacobs outlines this “fad” cycle
by describing her neighborhood, on Eighth Street in Greenwich
Village.
It started out as a “nondescript street” until Charles Abrams, one
of the principle property owners, built a small night club and
movie theater on the street. As they became popular and
successful, they changed the activity of the neighborhood,
bringing in more people during nights and weekends, which
added growth to the area in the form of special shops. These
shops brought even more people, during the day and evening,
and thus a variety of new and interesting restaurants. As the
restaurants were the most profitable per square foot of
enterprises on the street, restaurants bought out these unique
shops and nightclubs and varied use storefronts until the area no
longer had a diverse lineup of businesses.
The curse of border vacuums”. In this chapter, she
explains how massive elements like railways, parks,
hospital grounds, university campuses, etc. create
boundaries around them. They divide cities into pieces.
These boundaries eventually create a vacuum around
these spaces limiting people either within the
boundaries or outside them. These boundaries have
active physical and functional effects on their
neighbors. The negative impact can be seen
immediately next to the boundaries, as these spaces
usually tend to grow inwards.
There are many examples of such vacuums. These
include Central Park, Lower East Side and Morningside
Heights. Sometimes people and media add to this
vacuum; as was the case with Lower East Side. She
describes how a crime in Lower East Side reduced its
value and human interaction due to the excess media
attention that particular crime received. She calls such
spaces special lands as people walk around their
perimeter but not through them. On the other hand, a
general land is described as a space with regular
circulation of people. These general lands are
supposed to be most attractive areas and are not
usually adjoining the massive single elements. Thus,
she suggests increases interactions between inner and
outer areas of these elements to reduce vacuums
creating by boundaries of these spaces.

8. FORCES OF DECLINE AND REGENERATION
In chapter 15, Jane is talking about why some slums stay slums
and other slums regenerate themselves even against financial
and official opposition. Thus, she titles it “Unslumming and
slumming”.
According to Jane, slums operate as vicious circles. A slum is
usually caused by population instability; i.e. when people move
in and out too quickly, slums have low population. Slums tend to
spread and spreading slums require greater amounts of public
money. So the Urban Renewal planned a project to stop slums
by replacing them, but they failed. This is because replacing
them does not overcome problems that created these slums in
the first place.
She proposed that unslumming could happen only when
dwellers take an interest in improving area. People should make
slum dwellers desire to stay and develop neighborhoods instead
of unlumming slum. To make it clearer and better, diversity is the
key to unslumming, such as business growth or economic
developments. Moreover, respecting them, and understanding
their history will be an important key to help them.
In chapter 16 “Gradual money and cataclysmic money”, Jane
discusses money as a factor of decline and regeneration.
Specifically, three kinds of investment: (1) conventional,
nongovernmental, lender credit, (2) governmental money (by
taxes or government borrowing power) and (3) “shadow world”
money, made and spent illegally. All three types of money are
responsible for what Jacobs refers to as “cataclysmic” changes in
cities. This cataclysmic change, as opposed to gradual change, is
not natural or stable. Decay is linked to these forms of
investment through a cycle, beginning with the withdrawal of
conventional money.
From there, the area is run by shadow money, as it
dips into despair. Then, planners eventually select
the area as a candidate for cataclysmic
government money for clearance and renewal. This
last step does not encourage mixed use and
continues to destroy diversity.
Through this section, outlines four forces of decline for
a city:
(1) successful diversity as a self-destructive factor,
(2) deadening influence of massive single elements,
(3) population instability as an obstacle to diversity
growth and
(4) effects of public and private money.
However, she does not stop at simply defining the
problems. She also points out solutions to each
problem:
(1) diverse lineup of businesses to avoid self-
destruction of diversity,
(2) increased interactions between the outer and inner
areas of massive single elements,
(3) solving problems leading to slums rather than
unslumming them and
(4) creating a balance between general and cataclysmic
money in areas.

9. DIFFERENT TACTICS
Different Tactics offers concrete tools to improve cities. These
include increasing subsidized housing, reducing the number and
use of automobiles by improving public transportation, enhancing
the visual order of cities without sacrificing diversity, salvaging
housing projects, and revamping governing and planning districts.
Subsidizing dwellings
What is the reason for subsidizing dwellings in cities?
The answer we long ago accepted went like this: The reason we need
dwelling subsidies is to provide for that part of the population which
cannot be housed by private enterprise.
And, the answer went on, so long as this is necessary anyway, the
subsidized dwellings should embody and demonstrate the principles of
good housing and planning.
It is wrong to set one part of the population, segregated by income,
apart in its own neighborhoods with its own different scheme of
community. Separate but equal makes nothing but trouble in a society
where people are not taught that caste is apart of the divine order.
Separate but better is an innate contradiction wherever the
separateness is enforced by one form of inferiority.
Erosion of cities or attrition of automobiles
For people to live or work in such inconvenient cities, automobiles
would be necessary to spare them from vacuity, danger and utter
institutionalization.
It is questionable how much of the destruction wrought by automobiles
on cities is really a response to transportation and traffic needs, and
how much of it is owing to sheer disrespect for other city needs, uses
and functions.
There is another difficulty behind pedestrian schemes. Most city enterprises
which are a response to pedestrian street use, and which, reciprocally,
generate more pedestrian street use, themselves need convenient access
to vehicles for services, supplies or transport of their own products.
If vehicular and pedestrian traffic are completely separated, one of two
alternatives must be accepted. The first alternative is that the preserves for
the pedestrians must be streets which do not contain such enterprises. This
is automatically an absurdity. These absurdities can be found, in real life,
and just as might be expected, the preserves are empty. The pedestrians
are in the vehicular streets, where the enterprises are. This type of built-in
contradiction afflicts much grandiose "city of tomorrow" planning. The
other alternative is that it is necessary to devise schemes of vehicular
servicing, separated from the pedestrian preserves.
The problem that lies behind consideration for pedestrians, as it lies behind
all other city traffic difficulties, is how to cut down absolute numbers of
surface vehicles and enable those that remain to work harder and more
efficiently.
Visual order: its limitations and possibilities
We need art, in the arrangements of cities as well as in the other realms of
life, to help explain life to us, to show us meanings, to illuminate the
relationship between the life that each of us embodies and the life outside
us.
The limitations on possibilities and the strictures on individuals in such
societies extend much beyond the materials and conceptions used in
creating works of art from the grist of everyday life. The limitations and
strictures extend into every realm of opportunity (including intellectual
opportunity) and into relationships among people themselves.
All various tactics for capturing city visual order are concerned with bits
and pieces in the city—bits and pieces which are, to be sure, knit into a city
fabric of use that is as continuous and little cut apart as possible. But
emphasis on bits and pieces is of the essence: this is what a city is, bits and
pieces that supplement each other and support each other.

10. DIFFERENT TACTICS
Salvaging projects
One of the unsuitable ideas behind projects is the very notion that they
are projects, abstracted out of the ordinary city and set apart.
In the case of housing projects, the fundamental problems can be much
like those presented by unplanned, low-vitality gray areas and engulfed
former suburbs. In the case of nonresidential projects, such as cultural
or civic centers, the fundamental problems can be much like those
presented by has-been parts of downtowns which have suffered the
self-destruction of diversity.
The projects that today most urgently need salvaging are low-income
housing projects. Their failures drastically affect the everyday lives of
many people, especially children. Moreover, because they are too
dangerous, demoralizing and unstable within themselves, they make it
too hard in many cases to maintain tolerable civilization in their
vicinities.
Projects like any slums, need to be unslummed. This means, among
other things, that they must be capable of holding their populations
through choice. It means they must be safe and otherwise workable for
city life. They need, among other things, casual public characters, lively,
well-watched, continuously used public spaces, easier and more natural
supervision of children, and normal city cross-use of their territory by
people from outside it. In short, in the process of being rejoined into
the city fabric, these projects need to take on the qualities of healthy
city fabric themselves.
Governing and planning districts
Planning for vitality must stimulate and catalyze the greatest possible
range and quantity of diversity among uses and among people
throughout each district of a big city and this is the underlying
foundation of city economic strength, social vitality and magnetism.
Planning for vitality must promote continuous networks of local street
neighborhoods, whose users and informal proprietors can count to the
utmost in keeping the public spaces of the city safe, in handling
strangers so they are an asset rather than a menace, in keeping casual
public tabs on children in places that are public.
Planning for vitality must combat the destructive presence of border vacuums,
and it must help promote people's identification with city districts that are
large enough and are varied and rich enough in inner and outer contacts to
deal with the tough, inescapable, practical problems of big-city life.
Planning for vitality must aim at unslumming the slums, by creating
conditions aimed at persuading a high proportion of the indigenous
residents, whoever they may be, to stay put by choice over time, so there will
be a steadily growing diversity among people and a continuity of community
both for old residents and for newcomers who assimilate into it.
Planning for vitality must convert the self-destruction of diversity and other
cataclysmic uses of money into constructive forces, by hampering the
opportunities for destructiveness on the one hand, and on the other hand by
stimulating more city territory into possessing a good economic environment
for other people's plans.
Planning for vitality must aim at clarifying the visual order of cities, and it
must do so by both promoting and illuminating functional order, rather than
by obstructing or denying it.
The kind of problem a city is
Thinking has its strategies and tactics, one of the main things to know is what
kind of problem cities pose, for all problems cannot be thought about in the
same way. To understand what the changes in strategies of thought have to
do with cities, it is necessary to understand a little about the history of
scientific thought.
In principle, these are much the same tactics as those that have to be used to
understand and to help cities. In the case of understanding cities, I think the
most important habits of thought are these:
1. To think about processes;
2. To work inductively, reasoning from particulars to the general, rather than
the reverse;
3. To seek for "unaverage" clues involving very small quantities? which reveal
the way larger and more "average" quantities are operating.
Objects in cities, whether they are buildings, streets, parks, districts,
landmarks, or anything else, can have radically differing effects, depending
upon the circumstances and contexts in which they exist. Vital cities have
marvelous innate abilities for understanding, communicating, contriving and
inventing what is required to combat their difficulties.