Sustainable Street Network Principles - CNU

S U S TA INABLE STREET NETWORK PRINCIPLESC N U P R O J E C T F O R T R A N S P O R TAT I O N R E F O R MSustainable StreetNetwork PrinciplesCONGRESS FOR THE NEW URBANISMi

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C N U P R O J E C T F O R T R A N S P O R TAT I O N R E F O R MSustainable StreetNetwork PrinciplesCONGRESS FOR THE NEW URBANISM

S U S TA INABLE STREET NETWORK PRINCIPLES1PREAMBLEThe Congress for the New Urbanism recognizesthat cities—within the context of their surroundingregions—are the social, cultural, and economicfoundation of human civilization. We assertthat the street network provides the settingfor commerce and social interaction, and thatconstruction, operation, and maintenance of thestreet network is primarily to serve people andsociety.

2CNU PROJE C T F O R T R A N S P O RTAT I O N R E F O R MWe assert that current transportation engineeringaddresses only limited individual componentsof the region’s street network. This results in afragmented and inefficient system that fails toadequately engage the social, environmental, andeconomic aspirations of communities.We advocate a return to the historic understandingof the street network as a fundamental frameworkfor safe, livable communities, where the humanscale of the individual and the act of walkingrepresent the basic unit of design.

S U S TA INABLE STREET NETWORK PRINCIPLES3We dedicate ourselves to re-establishing therelationship between the street network and naturalsystems. Instead of degrading the environment anddepleting natural resources, street networks mustsupport and sustain the ecology of place.We believe that our scarce economic resourcesshould focus on opportunities rather thanproblems, and that funding for the street networkmust respond to rational economic factors.We propose the following principles to guidepublic policy, development practice, transportationplanning and engineering, and urban design.

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S U S TA INABLE STREET NETWORK PRINCIPLESPRINCIPLE 1C R E AT E A S T R E E T N E T W O R K T H AT S U P P O R T SCOMMUNITIES AND PLACESStreet networks fulfill a basic need in human society. Theyconnect people to each other and to destinations. Street networksare not just about transportation and infrastructure, but alsoabout the movement of people, goods, ideas, and wealth. Theyfoster economic activity and provide public space for humaninteraction. Street networks form an effective, flexible frameworkfor building a community, in every sense of the word.5

6CNU PROJE C T F O R T R A N S P O RTAT I O N R E F O R MPRINCIPLE 2C R E AT E A S T R E E T N E T W O R K T H AT AT T R A C T S A N DSUSTAINS ECONOMIC ACTIVITYStreet networks provide a template for a rich combination ofhousing, shopping, and transportation choices. They support arobust mix of culture and commerce. Sustainable street networksare magnets for business, light industry, jobs, and economicopportunities.

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S U S TA INABLE STREET NETWORK PRINCIPLESPRINCIPLE 3M A X I M I Z E T R A N S P O R TAT I O N C H O I C EAll people should be able to travel within their community in asafe, dignified and efficient manner. A sustainable street networkmakes that possible and ensures a choice of transportation modesand routes. People can walk, bicycle, take transit, or use a vehicle.Each mode is integrated, as appropriate, within each street. Asustainable street network gets you to your destination, and back.9

10CNU PROJE C T F O R T R A N S P O RTAT I O N R E F O R MPRINCIPLE 4I N T E G R AT E T H E S T R E E T N E T W O R K W I T HN AT U R A L S Y S T E M S AT A L L S C A L E SA sustainable street network respects, protects and enhances thenatural features and ecological systems of its urban environment.The result? A balanced and symbiotic community. It integratesstormwater treatment into street design and incorporatesstormwater flow and wildlife habitat zones into the streetnetwork. The sustainable street network responds to naturalfeatures, resources, and systems by adjusting street density andconnectivity. The sustainable street network considers the broadspectrum of relationships to natural systems, including thosethat are site specific, regional, and global.

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S U S TA INABLE STREET NETWORK PRINCIPLESPRINCIPLE 5R E S P E C T T H E E X I S T I N G N AT U R A LA N D B U I LT E N V I R O N M E N TThe scale and orientation of streets in the network celebratethe unique local and regional characteristics of the natural andbuilt environment. These include architectural features, climate,geography, topography, and history.13

14CNU PROJE C T F O R T R A N S P O RTAT I O N R E F O R MPRINCIPLE 6EMPHASIZE WALKING AS THE FUNDAMENTAL UNITOF THE STREET NETWORKOur most valued urban places are principally designed for theuse and enjoyment of people on foot. This requires a finely wovenfabric of streets and blocks that offer direct, varied pedestrianroutes made interesting through careful design.

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S U S TA INABLE STREET NETWORK PRINCIPLESPRINCIPLE 7C R E AT E H A R M O N Y W I T H O T H E RT R A N S P O R TAT I O N N E T W O R K SThe street network is a foundation for the design and evolutionof other transportation systems, including highways, rail, freightand air travel. A sustainable street network integrates thesesystems. It provides flexible mobility, easy and legible movementbetween modes, and helps turn transit meeting points intoattractive and valuable civic places.17

18CNU PROJE C T F O R T R A N S P O RTAT I O N R E F O R MKey Characteristic 1A web of streets and travel modes thatmaximize connectivityWell-connected street networks improve mobility byallowing people to travel more directly. This makesdestinations more accessible by walking, and enlarges thecapture area surrounding transit stations. Such highlyconnected street networks have been shown to reducevehicle miles traveled, traffic congestion, and vehicledelay. They permit traffic to diffuse across the largerstreet network when demand becomes excessive on anyindividual route. They have also been proven to reduceemergency response times.

S U S TA INABLE STREET NETWORK PRINCIPLESKey Characteristic 2Desirable places where multiplenetworks overlapThere are multiple mode-specific networks and insome places they overlap. For example, pedestrian, bike,transit, and car networks may overlap on the street. Inother places they may be separate, on trails or rails. Thesustainable street network coordinates these connectionsand creates a quality environment where they overlap.19

20CNU PROJE C T F O R T R A N S P O RTAT I O N R E F O R MKey Characteristic 3Inherently complexSustainable street networks feature a rich array of streetand route types—rather than just the same “flat” designused many times over. The amount and variety of streetsdetermine a community’s character, and whether itfunctions as a coherent whole or as disconnected islandsseparated by a few big streets.One flaw of contemporary network practice is abranching hierarchy in which local streets only flowto collectors and collectors only flow to arterials. Theconventional dendritic pattern creates highly specializedstreets that skew traffic volumes toward the arterialsystem and encourage high speeds throughout.By contrast, sustainable street networks connect alltypes of streets with one another. Boulevards, mews,avenues, and alleys all intersect. Individual streets can beless specialized, vehicle speeds can be reduced, and thenetwork can function more efficiently.

S U S TA INABLE STREET NETWORK PRINCIPLESKey Characteristic 4Major streets designed and spacedproperlyIn a sustainable street network, major streets are the“Great Streets” of their cities and towns. These streets,generally classified as arterials and collector streets, aremultimodal and designed to integrate with adjacentland uses.These streets have the greatest potential for large-scaleplacemaking and for providing physical space for social,civic, and commercial activity. The street design mayaccommodate different modes and different speedswithin a single cross section. For instance, a multiwayboulevard can support faster speeds in the center, andslower speeds and different modes–cycling and walking–in the outside lanes.Spacing major streets too far apart forces them to havemultiple lanes to carry cars. That impacts their potentialpedestrian and bicycle use and severely erodes theirplacemaking capacity. Inadequate street spacing alsocauses motorized traffic to encroach on neighborhoodroutes designed only for lighter traffic volumes. Wheretransit routes align with boulevards and avenues, streetspacing affects the efficiency and accessibility of transitservice. Proper spacing and design of major streets alsomitigates detrimental air quality and health impacts onsurrounding neighborhoods.21

22CNU PROJE C T F O R T R A N S P O RTAT I O N R E F O R MKey Characteristic 5All streets safe and walkableAll streets are safe and walkable in a sustainablestreet network, no matter how many vehicles theyaccommodate, or how continuous they are acrosssections of a town, city, or region. This is both a safetyand a public health issue. The design of street networkshas a profound effect on physical inactivity and trafficfatalities. Sustainable street networks support travel byactive modes—such as walking and bicycling—therebyincreasing physical activity and reducing obesity.These networks also help moderate the driving behaviorsthat cause traffic accidents. Drivers must learn to watchfor pedestrians, bicyclists and transit users everywhere.Street networks help achieve speed management goals,in both urban and suburban areas. It paves the way tocreation of safe, healthy, vibrant neighborhoods.

S U S TA INABLE STREET NETWORK PRINCIPLESKey Characteristic 6Wide variety of street types, each witha role in the networkThe sustainable street network consists of all types ofstreets that accommodate many different travel modes.Some streets are designed to serve traffic in all forms.Others are designed to be quiet with only the occasionalvehicle. Some span across a city, while others are lesscontinuous to control traffic speed and volume.In a sustainable street network, all streets have a role andare designed to serve the people of the community—today and well into the future.23