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Grid plan
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===Social environment and security=== In his seminal 1982 study on livable streets that was conducted in neighbourhoods with a grid, Donald Appleyard showed that social networking and street playing degraded as traffic increased on a street. His research provided the groundwork for [[traffic calming]] and for several initiatives such as [[living street]]s and [[Home Zone]]s, all of which are aimed at improving a street's social milieu. The amount of traffic on a street depends on variables such as the population density of the neighbourhood, car ownership and its proximity to commercial, institutional or recreational edifices. Most importantly, however, it depends on whether a street is or could become a through road to a destination. As a through road, it could sustain unpredictable levels of traffic that may fluctuate during the day and increase over time. A key characteristic of the grid pattern is that any and all streets are equally accessible to traffic (non-hierarchical) and could be chosen at will as alternative routes to a destination. Cut-through driving, or shortcutting, has been resisted by residents.<ref>Philip Langdon, 2006: Seaside Stews Over Street Connections. ''New Urban News'', September 2006</ref> Cities responded by making modifications to prevent it. Current recommended design practice suggests the use of 3-way intersections to alleviate it.<ref>{{cite web |url=http://www.cues.fau.edu/cnu/docs/Traditional_Neighborhood_Development_Street_Design_Guidelines-ITE.pdf |title=Traditional Neighborhood Development Street Design Guidelines |publisher=[[Institute of Transportation Engineers]] |date=October 1999 |location=Washington, DC |archive-url=https://web.archive.org/web/20110220174833/http://www.cues.fau.edu/cnu/docs/Traditional_Neighborhood_Development_Street_Design_Guidelines-ITE.pdf |archive-date=February 20, 2011 |access-date=May 23, 2017 }}</ref> The geometry of the normal, open grid is evidently unsuitable for protecting or enhancing the social environment of a street from the negative influence of traffic. The scale of the block, as argued by [[Jane Jacobs]]—writer and activist, in her landmark ''The Death and Life of Great American Cities'' (1961), is "one of the four most important factors in generating diversity".<ref name=":3">{{Cite web |title=small blocks |url=http://npl.wiki/view/small-blocks |access-date=2025-04-03 |website=npl.wiki}}</ref> Blocks longer than 400 feet (about 120 meters) disrupt the “intricate pools of fluid street use” that are necessary to support diverse economic and cultural interactions, and to maintain a “fabric of intimate economic cross-use”.<ref name=":3" /> Another key aspect is the overall street connectivity pattern, where smaller block sizes are crucial for enhancing accessibility, in addition to irregular block dimensions that emulate pedestrian movement. [https://www.ucl.ac.uk/bartlett/news/2019/nov/tribute-bill-hillier Bill Hillier], a professor of Architectural and Urban Morphology and his colleagues developed a “space syntax” model for street design, demonstrating that natural pedestrian movement—including trips to commercial areas—relies on the broader structure of the street grid. This supports Jacobs’ observation that block sizes directly influence economic activity and social interactions.<ref name=":3" /> Similarly, a 1972 ground-breaking study by [[Oscar Newman (architect)|Oscar Newman]] on a [[Defensible Space Theory]] described ways to improve the social environment and security of neighbourhoods and streets. In a practical application of his theory at Five Oaks, the neighbourhood's grid pattern was modified to prevent through traffic and create identifiable smaller enclaves while maintaining complete pedestrian freedom of movement. The positive outcome of these changes reinforces Appleyard's findings and the need to reduce or prevent through traffic on neighbourhood streets; a need that cannot be met with a typical, uniform, open grid. The question of neighbourhood security has been a constant focus of research since Oscar Newman's work. New research has expanded the discussion on this disputed issue. A recent study<ref>Hillier, Bill and Sahbaz, Ozlem (March 2008) "An evidence based approach to crime and urban design Or, can we have vitality, sustainability and security all at once?" Bartlett School of Graduate Studies, [[University College London]]</ref> did extensive spatial analysis and correlated several building, site plan and social factors with crime frequencies and identified subtle nuances to the contrasting positions. The study looked at, among others, dwelling types, unit density (site density) movement on the street, culs–de-sac or grids and the permeability of a residential area. Among its conclusions are, respectively, that flats are always safer than houses and the wealth of inhabitants matters, density is generally beneficial but more so at ground level, local movement is beneficial, but not larger scale movement, relative affluence and the number of neighbours have a greater effect than either being on a cul-de-sac or being on a through street. It also re-established that simple, linear cul-de-sac with good numbers of dwellings that are joined to through streets tend to be safe. As for permeability, it suggests that residential areas should be permeable enough to allow movement in all directions but no more. The overprovision of poorly used permeability is a crime hazard. The open, uniform grid could be seen as an example of undifferentiated permeability. A recent study in California<ref>Handy, Susan; Sommer, Samantha; Ogilvie, Julie; Cao, Xinyu; and [[Patricia Mokhtarian|Mokhtarian, Patricia]] (2007) "Cul-de-Sacs and Children's Outdoor Play: Quantitative and Qualitative Evidence" [[University of California, Davis]]</ref> examined the amount of child play that occurred on the streets of neighbourhoods with different characteristics; grid pattern and culs-de-sac. The findings indicate that the open grid streets showed substantially lower play activity than the cul-de-sac street type. Culs-de-sac reduce [[Perceived risk|perceived danger]] from traffic, and thereby encourage more outdoor play. It pointed the way toward the development of hybrid street network patterns that improve pedestrian movement but restrict cut-through driving. Similar studies in Europe<ref>Huttenmoser, Marco and [[Marie Meierhofer]] (1995) "Children and Their Living Surroundings for the Everyday Life and Development of Children." Children's Environments 12(4): 1-17</ref> and most recently in Australia<ref>{{cite journal | last1 = Veitch | first1 = Jenny | last2 = Salmon | first2 = Jo | last3 = Ball | first3 = Kylie | name-list-style= amp | year = 2010 | title = Individual, social and physical environmental correlates of children's active free-play: a cross-sectional study | journal = International Journal of Behavioral Nutrition and Physical Activity | volume = 7 | page = 11 | doi = 10.1186/1479-5868-7-11 | pmid = 20181061 | pmc = 2841089 | doi-access = free }}</ref> found that children's outdoor play is significantly reduced on through roads where traffic is, or perceived by parents to be, a risk. As a result of this misperception of risk, children living in cul-de-sac communities are more likely to be killed by vehicles. This increased risk of death is due to multiple factors, including the families driving longer distances to reach their destinations, parents spending less time teaching their children to be as wary of traffic, and an increased risk of the parents accidentally driving over the children in their "safe" driveways and cul-de-sac streets.<ref>[https://www.npr.org/templates/story/story.php?storyId=5455743 Cul-de-Sacs: Suburban Dream or Dead End?], Morning Edition on NPR</ref><ref>{{Cite web|url=http://bettercities.net/article/tomorrow%E2%80%99s-cities-tomorrow%E2%80%99s-suburbs|title=Tomorrow's Cities, Tomorrow's Suburbs | Better! Cities & Towns Online|archive-url=https://web.archive.org/web/20170118041952/http://bettercities.net/article/tomorrow%E2%80%99s-cities-tomorrow%E2%80%99s-suburbs|archive-date=2017-01-18|url-status=dead|access-date=2019-07-20}}</ref><ref>{{cite web|url=https://usa.streetsblog.org/2011/06/07/cul-de-sacs-are-killing-us-public-safety-lessons-from-suburbia/|title=Cul-de-Sacs Are Killing Us: Public Safety Lessons From Suburbia|date=7 June 2011}}</ref> Traditional street functions such as kids' play, strolling and socializing are incompatible with traffic flow, which the open, uniform grid geometry encourages. For these reasons, cities such as [[Berkeley, California]], and [[Vancouver, British Columbia]], among many others, transformed existing residential streets part of a grid plan into permeable, linked culs-de-sac. This transformation retains the [[Permeability (spatial and transport planning)|permeability]] and connectivity of the grid for the active modes of transport but filters and restricts car traffic on the cul-de-sac street to residents only.
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