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1.4. 400M Through Street Network

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(Weitergeleitet von 400M Through Street Network)

Within a Polycentric Region, we need to establish a balance between vehicular mobility and pedestrian safety, while maintaining, as much as possible, a continuous connectivity through the urban region.


01 4 01 400M Through Street Network


Problem-statement: At a larger urban scale, there is need for higher-speed vehicular mobility. But at a smaller sub-neighborhood scale, there is a need for resident-pedestrians to have a quieter area, free of the dangers and disruptions fast-moving vehicles.


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Discussion:: In many cities around the world, there is a surprisingly consistent pattern of through vehicular streets, spaced at roughly 400 meters or ¼ mile, or less. This pattern long predates the automobile, a fact that is not so surprising when we consider that vehicles of various kinds (carts, carriages, etc.) have existed in cities for millennia, and that these vehicles all pose some dangers to pedestrians. It seems that neighborhoods have self-organized to achieve a balance between the needs for pedestrian protection and vehicular mobility, by creating a protective zone (or “sanctuary,” as described by Donald Appleyard) that is roughly equal to an easy walk, or slow drive, to the nearest vehicular street. That distance is about 200 meters, or 400 meters in diameter.¹


400M Through Street Network
400M Through Street Network
The striking pattern of roughly 400m spacing of principal through avenues and “sanctuaries” in Bologna, Italy.
The same pattern can be seen in many other cities around the world.


It is important to understand that this pattern does not require a regular grid, or standard block sizes, although many cities (especially older cities in the United States) do in fact have the 400-meter pattern within a regular grid, and often with standard-sized blocks. The pattern also does not prohibit some smaller streets from aligning within these 400-meter zones or through their edges. It only requires that these smaller streets do not accommodate fast-moving vehicles, traveling relatively straight for long uninterrupted distances (typically 3 kilometers or 2 miles).


400M Through Street Network
400M Through Street Network
This illustration (not to scale) shows that regular blocks and street grids are not required for the pattern,
and a much more irregular pattern of principal through avenues at 400m (as shown below) is possible.


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Therefore:

When laying out street grids, use a rough spacing of 400m (¼ mile) or less for principal through streets. Within these roughly 400m areas or “sanctuaries,” make shorter, interrupted, lane-like streets that accommodate vehicles, but allow pedestrians to dominate.



400M Through Street Network
400M Through Street Network


At larger scales, accommodate higher-speed mobility with the Multi-Way Boulevard that combines mobility with safe paths and crossings for pedestrians and bicycles. Where the highest speeds are required, use a Mobility Corridor with grade-separated pedestrian and bicycle paths, and crossings at no more than 400 meters. At smaller scales, use the Avenue and Shared Space Lane patterns…




¹ This concept was examined at length in Mehaffy M.W., Porta, S., Rofè, Y. and Salingaros, N. (2010), Urban nuclei and the geometry of streets: The ‘emergent neighborhoods’ model. Urban Design International, 15(1), 22-46.

SECTION I:

PATTERNS OF SCALE


1. REGIONAL PATTERNS

Define the large-scale spatial organization…

1.1. POLYCENTRIC REGION

1.2. BLUE-GREEN NETWORK

1.3. MOBILITY CORRIDOR

1.4. 400M THROUGH STREET NETWORK

2. URBAN PATTERNS

Establish essential urban characteristics…

2.1. WALKABLE MULTI-MOBILITY

2.2. LEVEL CITY

2.3. PUBLIC SPACE SYSTEM

2.4. BIOPHILIC URBANISM

3. STREET PATTERNS

Identify and allocate street types…

3.1.URBAN GREENWAY

3.2. MULTI-WAY BOULEVARD

3.3. AVENUE

3.4. SHARED SPACE LANE

4. NEIGHBORHOOD PATTERNS

Define neighborhood-scale elements…

4.1. STREET AS CENTER

4.2. PEDESTRIAN SANCTUARY

4.3. NEIGHBORHOOD SQUARE

4.4. NEIGHBORHOOD PARK

5. SPECIAL USE PATTERNS

Integrate unique urban elements with care…

5.1. SCHOOL CAMPUS

5.2. MARKET CENTER

5.3. INDUSTRIAL AREA

5.4. HOSPITAL

6. PUBLIC SPACE PATTERNS

Establish the character of the crucial public realm…

6.1. PLACE NETWORK

6.2. WALKABLE STREETSCAPE

6.3. MOVABLE SEATING

6.4. CAPILLARY PATHWAY

7. BLOCK AND PLOT PATTERNS

Lay out the detailed structure of property lines…

7.1. SMALL BLOCKS

7.2. PERIMETER BLOCK

7.3. SMALL PLOTS

7.4. MID-BLOCK ALLEY

8. STREETSCAPE PATTERNS

Configure the street as a welcoming place…

8.1. STREET AS ROOM

8.2. TERMINATED VISTA

8.3. STREET TREES

8.4. STREET FURNISHINGS

9. BUILDING PATTERNS

Lay out appropriate urban buildings…

9.1. PERIMETER BUILDING

9.2. ARCADE BUILDING

9.3. COURTYARD BUILDING

9.4. ROW BUILDING

10. BUILDING EDGE PATTERNS

Create interior and exterior connectivity…

10.1. INDOOR-OUTDOOR AMBIGUITY

10.2. CIRCULATION NETWORK

10.3. LAYERED ZONES

10.4. PASSAGEWAY VIEW



SECTION II:

PATTERNS OF MULTIPLE SCALE


11. GEOMETRIC PATTERNS

Build in coherent geometries at all scales…

11.1. LOCAL SYMMETRY

11.2. SMALL GROUPS OF ELEMENTS

11.3. FRACTAL PATTERN

11.4. FRAMING

12. AFFORDANCE PATTERNS

Build in user capacity to shape the environment…

12.1. HANDLES

12.2. CO-PRODUCTION

12.3. FRIENDLY SURFACES

12.4. MALLEABILITY

13. RETROFIT PATTERNS

Revitalize and improve existing urban assets …

13.1. SLUM UPGRADE

13.2. SPRAWL RETROFIT

13.3. URBAN REGENERATION

13.4. URBAN CONSOLIDATION

14. INFORMAL GROWTH PATTERNS

Accommodate “bottom-up” urban growth…

14.1. LAND TENURE

14.2. UTILITIES FIRST

14.3. DATA WITH THE PEOPLE

14.4. INCREMENTAL SELF-BUILD

15. CONSTRUCTION PATTERNS

Use the building process to enrich the result…

15.1. DESIGN-BUILD ADAPTATION

15.2. HUMAN-SCALE DETAIL

15.3. CONSTRUCTION ORNAMENT

15.4. COMPLEX MATERIALS



SECTION III:

PATTERNS OF PROCESS


16. IMPLEMENTATION TOOL PATTERNS

Use tools to achieve successful results…

16.1. FORM-BASED CODE

16.2. ENTITLEMENT STREAMLINING

16.3. NEIGHBORHOOD PLANNING CENTER

16.4. COMMUNITY MOCKUP

17. PROJECT ECONOMICS PATTERNS

Create flows of money that support urban quality…

17.1. TAX-INCREMENT FINANCING

17.2. LAND VALUE CAPTURE

17.3. EXTERNALITY VALUATION

17.4. ECONOMIES OF PLACE AND DIFFERENTIATION

18. PLACE GOVERNANCE PATTERNS

Processes for making and managing places…

18.1. SUBSIDIARITY

18.2. POLYCENTRIC GOVERNANCE

18.3. PUBLIC-PRIVATE PLACE MANAGEMENT

18.4. INFORMAL STEWARDSHIP

19. AFFORDABILITY PATTERNS

Build in affordability for all incomes…

19.1. INTEGRATED AFFORDABILITY

19.2. COMMUNITY LAND TRUST

19.3. MULTI-FAMILY INFILL

19.4. SPECULATION TAX

20. NEW TECHNOLOGY PATTERNS

Integrate new systems without damaging old ones…

20.1. SMART AV SYSTEM

20.2. RESPONSIVE TRANSPORTATION NETWORK COMPANY

20.3. AUGMENTED REALITY DESIGN

20.4. CITIZEN DATA