Street hierarchy: Difference between revisions

Revision as of 01:30, 10 January 2024

Revision as of 21:21, 28 January 2024

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{{Short description|Urban planning restricting through traffic of automobiles}}

{{Multiple issues|

{{Original research|date=October 2023|reason=Several paragraphs contain unsourced information on a niche subject.}}

{{more citations needed|date=July 2019}}

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[[File:Radburn Cellular Street Pattern.jpg|thumb|300px|right|The network structure of [[Radburn, New Jersey]] exemplifies the concept of street hierarchy of contemporary districts. (The shaded area was not built.)]]

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====Safety====

Transportation planners and traffic engineers have expressed concerns over the traffic safety drawbacks presented by the street hierarchy. Recent studies have found higher traffic fatality rates in outlying suburban areas than in central cities and inner suburbs with smaller blocks and more-connected street patterns.<ref>http://www.minority.unc.edu:9014/sph/minconf/2004/materials/ewing.etal.pdf

{{deadlinkdead link|date=November 2020}}</ref><ref>{{cite web |url=http://www.virginia.edu/topnews/releases2002/lucy-april-30-2002.html |title=Archived copy |access-date=2006-09-03 |url-status=dead |archive-url=https://web.archive.org/web/20060903234004/http://www.virginia.edu/topnews/releases2002/lucy-april-30-2002.html |archive-date=2006-09-03 }}</ref> While some of this disparity is the result of distance from emergency medical facilities (hospitals are usually not built in a newly developed suburban area until a fairly late stage in its development), it is clear that the higher speeds engendered by the street hierarchy increase the severity of accidents occurring along arterial roads.

An earlier study<ref>Eran Ben-Joseph, Livability and Safety of Suburban Street Patterns: A Comparative Study (Berkeley, CA: Institute of Urban and Regional Development, University of California, Working Paper 641, 1995)</ref> found significant differences in recorded accidents between residential neighbourhoods that were laid out on an undifferentiated grid and those that included culs-de-sac and crescents in a hierarchical structure. The frequency of accidents was significantly higher in the grid neighbourhoods.

Two newer studies examined the frequency of collisions in two regional districts using the latest analytical tools. They investigated the potential correlation between street network patterns and frequency of collisions. In one study,<ref>Using Macrolevel Collision Prediction Models in Road SafetyPlanning Applications Gordon R. Lovegrove and Tarek Sayed Transportation Research Record: Journal of the Transportation Research Board, No. 1950, Transportation Research Board of the National Academies, Washington, D.C., 2006, pp. 73–82</ref> cul-de-sac hierarchical networks appeared to be much safer than the uniform grid networks, by nearly three to one.

A second study<ref>Sun, J. & Lovegrove, G. (2009). Research Study on Evaluating the Level of Safety of the Fused Grid Road Pattern, External Research Project for CMHC, Ottawa, Ontario</ref> found the grid plan to be the least safe by a significant margin with respect to all other street patterns.

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==Future prospects==

{{refimprovemore citations needed|section|date=November 2020}}

===United States===

While street hierarchies remain the default mode of suburban design in the United States, its 21st century usefulness depends on the prevalence of low density developments. To the degree that developable land becomes scarce in coastal urban areas and in geographically constrained inland cities such as [[Tucson, Arizona|Tucson]], [[Las Vegas, Nevada|Las Vegas]], and [[Salt Lake City, Utah|Salt Lake City]], the street hierarchy's inability to handle any but the lowest population densities is a long-term liability. The street hierarchy is also unpopular in the coastal city of [[New Orleans, Louisiana|New Orleans]] because of its geographic barriers, and because like Philadelphia, New York, and Cleveland, New Orleans already had suburbs before the new design became popular. Grids were used in New Orleans to fit a population that had at one time reached over 700,000 into {{convert|180|sqmi|km2}} of land with over 20 percent of that number being dedicated to uninhabitable wetlands. There a street hierarchy took up too much space to be economical. Real estate developers in areas with high land prices, such as Southern California's [[Inland Empire]], are finding that the relatively high population density of contemporary subdivisions is leading to severe traffic congestion on arterial roads that were country lanes a decade earlier. The street hierarchy is also becoming less attractive as awareness increases of the environmental consequences of the urban planning paradigm of which it is an integral part. The "[[smart growth]]" movement calls for street patterns with a high degree of connectivity, and with it a more balanced provision for various travel modes, both vehicular and non-vehicular.

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{{Road types}}

[[Category:Hierarchy]]

[[Category:Road transport]]