Sustainability is a term that has multiple definitions which are dependent upon the context in which it is represented. According to the New Merriam-Webster Dictionary, sustainability is defined as "provision of nourishment; endurance". This definition seems to fit a purely social context. However, our analysis focuses on planning for the future and reaching a balance between physical, social, cultural and economic elements of a neighborhood. A seemingly closer definition, as stated by the 1992 Rio Earth Summit, is one based on an environmental context. It states that sustainability" is the enablement of current populations to prepare and protect the environment for future generations". This definition holds true when looking at creating sustainability of the environment within the context of planning. It is very close to our goal of sustainability for neighborhoods but, not close enough. Given these previously mentioned definitions, none seem to fit into the framework of sustainable neighborhoods. However, this alludes to an important point: Sustainability is not one vision but many citizens' visions woven into a singular framework.

When looking at multiple citizens' visions of sustainability, there are several issues that come to the forefront: diversity, citizen involvement, meeting needs, engagement and making transitions.

Diversity
Diversity can foster success of communities, like neighborhoods. It is recognizing that these communities are made up of many different elements and support many different people. Importantly, diversity must be integrated into that singular vision.

Citizen Involvement
This issue is important because it is about the citizen gaining ownership. If a citizen contributes to the creation or formation of a vison, then they gain ownership. As a result, the citizen will be more inclined to fulfill aspects of that vision based on their personal investment.

Meeting Needs
Any vision of sustainability is about meeting the needs of the present and the future. If a human's needs are not met, then he/she will continue to find ways to meet their needs. These ways may not necessarily be beneficial in reaching that singular vision.

Engagement
Once a citizen has become involved and invested themselves, then they are able to attain a level of engagement. This can be accomplished by gaining knowledge through education or technology.

Making Transitions
Everyday humans make transitions, whether it is facing Colorado weather by wearing a short-sleeved shirt on a nice 70 degree day, returning home that evening and waking up the next moring to 7 inches of snow. As humans, we made a transition because we recognized the shifts in the weather patterns. As citizens, we must recognize these shifts within in our communities and personally act upon them by making transitions.

In addition to these issues at the forefront of building a single vision towards sustainability, one must look at the relationships and tradeoffs which occur within an existing or new community, like a neighborhood. There are 3 systems that are always in constant shift: carrying capacity, population and needs & behaviors.

1. Carrying Capacity
   This is the limit at which an organism or an environment can no longer sustain itself. For example, a system like infrastructure, more specifically a 4 lane highway, could possibly carry about 500 automobiles every 30 minutes.

2. Population
   If the population increases then the carrying capacity that the previously mentioned highway could exceed its limit by supporting extra automobiles.

3. Needs & Behaviors
   If the carrying capacity of this 4 lane highway is exceeded, then a shift in the realtionship between the car and the highway will have to occur. As humans, our behavior will affect that shift and our behaviors will be a direct result of how our needs are being met. In this example, a portion of the population recognized the environmental and financial costs that could be saved by making a tradeoff from driving a personal automobile to an alternative mode of transportation, like a bus. This tradeoff resulted in a shift away from pressuring the carrying capacity of the highway and reducing it to a normal level.

In creating sustainable neighborhoods, a definition of a neighborhood is necessary. A neighborhood can be defined as an identifiable spatial unit in which people belong to which defines those small human groups which create the energy and character that can bring the larger community, town/city as well as the mosaic of subcultures, to life (A Pattern Language).

Sustainable Neighborhood

A sustainable neighborhood is an inclusion of both the above- mentioned definitions. It has physical, social and economical sustainable elements that formulate its structure into an equitable balance within the size of a neighborhood.

* Size of a neighborhood

The size of a neighborhood is one of the first elements inherent to sustainability and our analysis. According to our research, a neighborhood that has a population between 500- 1000 people is relative to reaching a level of sustainability. The reasoning for this number is because individuals do not have an effective voice in any community larger than this size. The neighborhood is small enough to create a possible link between its inhabitants walking down the street and local representatives or officials. Citizens voices will be heard and recognized at this size.

* Neighborhood Boundary

The second important element to achieve sustainability in a neighborhood is to define a neighborhood boundary. This is based on physical and social needs. "The strength of the boundary is essential to a neighborhood. If a boundary is too weak the neighborhood will not be able to maintain its own identifiable character. An average neighborhood diameter is approximately 300 yards across with no more than 400 to 500 inhabitants within this area. From this designation, a boundary for the neighborhood can be defined. Boundaries are usually defined by roads which carry heavy amounts of traffic. These pathways protect the subcultures of the neighborhood and create spaces for transactions with surrounding functions. The Appleyard- Lintell study found that heavily traveled roads which acted as neighborhood boundaries was traveled by 200 cars per hour. It also said that any number of vehicles which exceed this number caused neighborhoods to deteriorate. Their reasoning is based on the fact that more vehicles become a threat to inhabitants of the neighborhood and they would be less likely to cross the street or venture outside to visit their neighbor.

* Meeting places

Once the boundaries are established, meeting places can be constructed for surrounding neighborhoods to share. This function encourages social interaction between other neighborhoods and amongst the neighbors themselves. Serving social needs helps to network neighborhoods so that they can learn and look to each other for social and physical provisions.

* Restricted Access

Also, boundaries aid in restricting access and limit the number of pathways and roads to and from the neighborhood. Placing main gateways at the routes that pass through the boundaries work concurrently with the boundaries to limit access. This aids in the protection of the neighborhood and keeps social and physical structure in place thus providing for a more sustainable future.

* Establishing A Visible Center

Establishing a visible center for the neighborhood is another sustainable element found in our analysis. A center for the neighborhood will give it a common focus that inhabitants can gather to. This focus can be a civic space, such as a park with benches and a fountain, or a community building such as a community center, a school, a library or even a church like in historical times. If a community or a neighborhood has a focus then it will influence the community to be physically and socially organized.

* Commercial

Commercial opportunities are also inherent to achieving sustainability of the neighborhood. It offers employment and enhancement of the local economy. This allows the community to maximize its profits for physical improvements within the neighborhood. It also encourages the location of neighbors in proximity to workplaces thus lessening the burden on transportation routes. Recommended commercial sites should be designed to fit within the scale of a neighborhood. Such examples are a street cafe, corner grocery store, artist gallery, dry cleaners, etc. These will supply the neighborhood with necessary commercial services and allow for citizens outside of the neighborhood boundary to participate also.