Design of Urban Space at Pedestrian Scale: A Method for Parameterization of Urban Qualities

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1 th International Conference on Information Visualisation Design of Urban Space at Pedestrian Scale: A Method for Parameterization of Urban Qualities Anastasia Koltsova, Antje Kunze, Gerhard Schmitt Chair of Information Architecture ETH Zurich Zurich, Switzerland koltsova@arch.ethz.ch, kunze@arch.ethz.ch, gerhard.schmitt@sl.ethz.ch Abstract This paper focuses on a method for parameterization of urban space at the pedestrian scale. There is a growing demand for new design approaches that would help to slow down urban sprawls, move away from modernist urban planning models and improve the quality of urban centers overall [15]. One important aspect that contributes to the overall sustainability of contemporary cities is the quality of pedestrian space. To enhance urban environment at pedestrian scale new design strategies must be investigated. Contemporary urban centers must provide various options for public transport, contain fine-grained urban functions, mixeduse building types and good-quality public open spaces to facilitate their use by pedestrians. The aim of this paper is a) to identify the initial set of design parameters of urban form at the pedestrian scale and b) to demonstrate the exemplary implementation of these parameters within parametric software, e.g. Grasshopper for Rhinoceros [26] and Esri CityEngine [25] for analysis, optimization and evaluation of urban settings. Keywords-urban design; parametric modeling; procedural modeling; design tools; pedestrian design I. INTRODUCTION The goal of the research work presented in this paper is to provide architects and urban designers with the design support tools that would facilitate the creation of qualitative urban space at the pedestrian scale. The provision for qualitative pedestrian space would reduce the need for private transportation, and, subsequently reduce fuel consumption and environmental pollution and contribute to the overall sustainability of contemporary cities. Urban design is a complex process that encompasses a number of disciplines and activities such as landscape and architectural design, town planning, property development, illustrating design principles and many more. It operates across various spatial scales: from a single settlement to architecture. Urban designers need to be constantly aware of scales above and below the scale at which they are operating, and also of the relationships fragments - whole entity and whole entity - fragments [40]. Urban design is a collaborative and interdisciplinary process. It involves an integrated approach and uses skills and knowledge of a wide range of participants (later in the text referred to as stakeholders). Such an approach implies collection and management of considerable amount of data. In order to simplify the data management and facilitate the communication process between stakeholders our research group develops parametric and procedural design support tools. These tools aim at visualizing, analyzing, and generating virtual urban design scenarios at various levels of urban scale (including pedestrian scale). One of the great challenges that is crucial for the development of design support tools is that much of the data in the design process has a non-mathematical nature. It is hard to identify the parameters of urban form that are quantifiable and that can be implemented within parametric/procedural software. This paper presents a method for parameterization of urban qualities at pedestrian scale developed through collaborative workshops with practicing architects and urban designers, teaching exercises and the review of urban design literature. II. RELATED WORK A. Decision support tools in urban planning According to Erhan [28], design support research emphasizes (a) how computers can assist designers, and in what area, (b) how design problems can be represented for computational support, (c) how computers can generate solutions using these representations, and (d) how computers can help to evaluate the quality of the generated solutions. In architectural and urban design, several design decision support tools exist [29, 30, 31, 32, 33, 38, 46]. However, new requirements arise for decision support tools that enhance the community design, e.g., in the field of participation, new urbanism and sustainability [34]. Kim and Clayton [8] describe the use of BIM and Object- Oriented Programming to support Form-Based Codes (FBC). FBC is a set of regulations that is used in the US to control urban development, primarily physical urban form. The parametric urban model is created to overcome existing limitations by using shared databases and relevant visualization. This tool can be used by the public sector to ensure that density and block geometry regulations are satisfied. At the same time, the private sector can use threedimensional FBC to obtain a clearer understanding of regulations and design feasibility. Müller et al. [24] introduced an attributed shape grammar, called CGA shape grammar targeted at the architectural design. It is the basis for the Esri CityEngine System. CityEngine can rapidly produce and visualize 3D /12 $ IEEE DOI /IV

2 urban environments of any size. Integrating shape grammars into the urban planning process offers unprecedented opportunities to understand and encode urban patterns [20, 23] and to generate and visually assess urban design scenarios [19, 21, 22]. Smart Solutions for Spatial Planning (SSSP) is another example of digital applications for urban design with more emphasis on large urban scale. Derix [2] described a digital chain (set of disintegrative tools) that covers geographic information system (GIS) mapping, accessibility and routes, urban structure generation, land-use and mix generation, and massing and density visualization. Some initial decision support tools have been developed as urban simulation models and implemented in regional planning processes [35, 36]. A further development is an environment supporting the interactive design of urban spaces that integrates behavioral and geometrical city modeling [37]. Urban design variables can be more intuitively accessed and visualized within such an environment, resulting in urban scenarios that consider the design of highways, accessibility studies, population and projected employment distribution. In general, the integration of the temporal scale along with 3D rendering could provide a very powerful and even more meaningful exploration of urban models. III. URBAN DESIGN DISCIPLINE First, confirm that you have the correct template for your paper size. This template has been tailored for output on the US-letter paper size. If you are using A4-sized paper, please close this template and download the file for A4 paper format called CPS_A4_format. The segregation of urban elements that followed the expansion of cities in the period after the WWII resulted from the planners` overreaction to complexities of the new industrial city and their aspiration to control it. The focus of modern planners was on individual city sectors and on private development while the design of public spaces was left intact and its quality rapidly deteriorated [41]. The discipline of urban design as we know it today was born in 1960s while searching for quality of urban space. During the course of the discipline development there emerged several schools of thought [40]: The visual-artistic tradition (for the most part end product-oriented, it followed visual qualities and aesthetic perception of urban space rather than any other factors such as social, economic, political, or spatial; Camillo Sitte); The social usage tradition (such traditions emphasize the way people use space and cover issues of perception and sense-of-place; Kevin Lynch, Jane Jacobs); The place-making tradition (combines the two earlier traditions) As a part of the place-making tradition, a few design theorists and practitioners such as Lynch [15, 16], Jacobs and Appleyard [9], [5, 6] and Tibbalds [39] worked to derive desirable qualities of effective urban places. In the course of our research we have reviewed the work of the aforemntioned design theorist in order to formulate the preliminary list of urban design qualities that we later translated into a set of design parameters for parametric and procedural models. IV. METHOD FOR PARAMTERIZATION OF URBAN QUALITIES This section presents a method for parameterization of urban qualities and their subsequent evaluation through parametrically and procedurally generated urban models (Figure 1). Figure 1. Diagram of the method for parameterization of urban qualities. In the first step, the urban design literature related to urban space quality was analyzed. The literature analysis resulted in an accumulative list of urban design qualities. In order to translate the selected qualities into parametric urban models we formulated a set of design parameters describing the urban form at the pedestrian scale. The last step was the implementation of the derived parameters in parametric software together with our students for the evaluation and revision of the selected quality criteria. The preliminary list of design parameters was added by our students in the course of their work on the design projects which will be described later in the text. 404

3 V. DERIVED URBAN DESIGN QUALITIES AND PARAMETERS Table 1 presents the selected urban design qualities and the derived parameters. TABLE I. LIST OF URBAN DESIGN QUALITIES AND DESIGN PARAMETERS FOR URBAN FORM AT THE PEDESTRIAN SCALE Urban Design Qualities Design Parameters Author Accessibility Accessibility of green areas Degree openess of Permeability of the edges Imageability Legibility Enclosure Linkage Distance between major functions (e.g. housing, retail and leisure facilities and transportation hubs); landscape undulation and pedestrian path configuration Area (amount) of building frontage obstructing an open space Area (amount) of building frontage obstructing an open space Physical access, noise penetration and emission Number of courtyards, plazas, and parks [#] Noise level [very quiet/quiet/ normal/loud/very loud] Memorable architecture [y/n] Limited view [y/n] Proportion sky [% sky ahead/sky across] Connectivity of green and open spaces [(no connectivity) (high connectivity)] Kevin Lynch (1981) Tibbalds et al. (1993) Stiles et al. Stiles et al. Tibbalds et al. (1993) Figure 2. Case study area region Limmattal with the two focus areas: Schlieren and Altstetten, Zurich. The region Limmattal is associated to the Zurich metropolitan area. The Zurich region is the most important economic Swiss region and has developed from an industrial city to a polycentric metropolitan region in the last 50 years [43]. More cities and villages close to Zurich get a metropolitan character [43]. The region Limmattal in the west of the city center has evolved from small villages along the river Limmat like a pearl necklace to a traditional expansion and industrial area. Today according to Diener, et al. [43] the Limmattal becomes more heterogeneous and fragmented. Although all 14 municipalities of the region Limmattal have their specific population and growth characteristics, they all share similar profiles such as a cardominated transit corridors and a valley that is densely covered with infrastructure facilities, settlements and that has only few protected green spaces inside [44]. In this paper we will focus on the two local case studies Schlieren (6.38 sq.km / people) and Altstetten (7.47 sq.km / people). The terminology used in this paper is derived from the classification of urban quality criteria encountered in the literature: for example (a) the classification of environmental quality factors provided in Tibbalds et al. [39], which include: legibility, identity and accessibility of green areas; (b) the classification of [5], which concentrates on the design qualities related to walkability, such as: imageability (e.g. noise level, major landscape features); enclosure (e.g. proportion street wall, proportion sky across); linkage (e.g. connections between public urban spaces); (c) the list of factors important for design of good urban space provided in Stiles et al. [42], which include: permeability of the edges (e.g. physical access, noise emission); and (d) one of the performance dimensions of urban space according to Lynch [15]: the accessibility. VI. CASE STUDY AREA: REGION LIMMATTAL Our case study area the region Limmattal (Figure 2) is an example for regions with strong attraction of medium size, linearity, dominant traffic infrastructure, industrialization, strong growth in inhabitants and jobs. VII. IMPLEMENTTATION OF PARAMETERS AND RESULTS For the evaluation of the derived urban qualities the two case study areas Altstetten and Schlieren, situated in the region Limmattal, were selected. Both case studies were introduced as project areas in the teaching exercises supervised by our research team. The focus of the first exercise was on the development of the procedural model for Altstetten. The second exercise concentrated on the development of parametric tools for the analysis of urban space qualities for the case study in Schlieren. A. Development of design guidelines The urban structure of Altstetten was analyzed during the field trips of the student course New Methods in Urban Simulations. The analysis resulted in a compilation of building and street types, open spaces, vegetation and zoning. The urban design qualities and design parameters in Table 1 were used as a reference to gather the design parameters for urban form at the pedestrian scale. 405

4 Figure 3. Public and private frontages of Rautistrasse, Zurich Altstetten Qualitative and quantitative parameters were documented in a survey and urban design qualities were measured and identified during a site visit to the local case study area Altstetten, Zurich. As a base for the survey of the qualitative parameters the SmartCode approach for the analysis of transect zones was used [27]. The method of [5] for identifying and measuring urban design qualities was adapted and extended with ecological, socio-economic and design parameters. Students documented their site visit (Figure 3). Design parameters of the street profiles, blocks, building geometries, facades, open spaces and vegetation were captured as conceptual sketches (Figure 4). Based on the derived parameters the design guidelines for the urban setting at pedestrian scale were established (Table 2). Scope Design parameters Design guidelines Lot Depth [m] All buildings have 54 a east-west Lot Coverage [%] orientation Block Dimension [m x Floor plan m] 19.5 x 39.6 influences volume. Lot Width [m] Balconies on south 30 and west side or Lot Depth [m] east side. 54 Lot Coverage [%] Building form Facade Open space Vegetation First Floor above Grade [m] 2.5 Number of courtyards, plazas, and parks [#] 4 Noise level normal Proportion of native vegetation [%] 50 Connectivity of green and open spaces [ ] 0 Entry and building is orientated to the yard. One entry per building. Parking area and green organic allotment area. Few trees 40 to 50 years old. Grass & shrubberies. B. Generation of urban patterns and synthesis in one parametric urban model A set of specific urban typologies was formulated and combined in urban patterns. Subsequently, a procedural urban model was developed in Esri CityEngine (Figure 5). Figure 4. Zurich Altstetten, Rautistrasse building form and east facade TABLE II. LIST OF THE USED DESIGN PARAMETERS AND DERIVED GUIDELINES FOR THE CASE STUDY, ZURICH ALTSTETTEN, RAUTISTRASSE Scope Design parameters Design guidelines Spatial Width [m] ~30 Street Width [m] 14 Street profile Moving Lanes [#] Raised pavements. 2 Planted central Parking Lanes [#] dividing strip (with road Sidewalk Width [m] 2 lighting). Proportion street wall: illdefined Proportion sky [% sky ahead] 50% Block Dimension [m x A block consists Block m] 19.5 x 39.6 of a building Lot Width [m] cluster ( buildings). Figure 5. Examples of the implementation of the case study Altstetten, Zurich (Hefti and Grewe-Rellmann) C. Analysis tools of urban settings Our second teaching exercise concentrated on the development of parametric urban analysis and design tools in the Grasshopper plug-in for Rhinoceros [26]. These tools 406

5 were applied to a case study in Schlieren located in the Limmattal Valley. The old part of the city developed on the slopes of the valley and was later extended by the industrial zone built between the river and the railway running through the city. Apart from the railway there are two major roads crossing the city, the Badenerstrasse and Bernstrasse (connecting Baden and Bern to Zurich respectively). As a result the city is split into separate zones, which makes pedestrian travel highly inconvenient. Therefore, we asked our students to look for the ways in which the city structure can be enhanced in order to facilitate its use by pedestrians. After the introduction students were asked to identify the design problem that they would like to explore. To a large extent the choice of students was dictated by the problems lying on the surface such as accessibility/navigation and the noise emission. The next sections present several examples of analysis tools that were developed by our students Urban space openness analysis. This parametric tool helps to visualize the openness of urban public spaces on a project site. The curves that represent the boundaries of the open space are subdivided into a number of points (point set 1). These points are then connected with lines to the set of points on curves that represent the rooftop boundaries of the surrounding buildings (point set 2). The algorithm checks that lines are created only between the point set 1 and the closest points in the point set 2. The lines connecting the two point sets are then used to create surfaces. Figure 6 illustrates the result where one can see the length of the vistas from different open spaces on the project site. The propagation of noise f(d) along the facade surface is assumed to be proportional to the inverse of the square root of the distance d : To get the amount of noise for each face of the façade surface we can calculate it as follows: where K is the constant amount of noise. The faces of building facades are colored based on the amount of received noise. In the next step students combined the 2D and 3D analysis to attain a complete picture. In the next steps we plan to incorporate the absorption of the facade surface and reflection as additional parameters. Figure 7. Traffic noise analysis in central Schlieren (Hefti, Meier, Zahno): (left) calculation of the 24-hour day cycle map of the traffic noise propagation, (right) 3D analysis of the noise load on simplified building facades and development of design iterations considering traffic noise, e.g. noise pushes the facades back and behind existing buildings, the volume expands. Figure 6. Connection between point set 1 (open space) and point set 2 (roof top), right: Visualization of the space openness on the project site in Schlieren (Bingyi Li, Christopher Choi, Yanchen Liu) D. Noise propagation This tool was developed by our students for the analysis of traffic noise propagation on a project area. The noise sources were the streets on a project site to which the corresponding traffic volume and subsequent amount of noise emission was linked (the data was taken from the GIS website). Students developed a Grasshopper definition that calculates the noise propagation on the 2D plane without any obstacles and in 3D on building facades (Figure 7). The calculation of the noise impact in 3D is based on the distance from the mid-point of each face of the facade surface to the closest point on the road. E. Bicycle route design Schlieren is bounded by the forest from the South and the river with promenade from the North. The distance between the two areas is too long to be covered on foot, however, it is perfect for bicycle trips. In order to link these two natural resources one of our students developed a tool that takes into account the terrain undulation and the existing streets to analyze the possible options for bicycle routes (Figure 8 and 9). The main parameters that are used in the system are: slope angle (defined threshold from 0 to 15 degrees), direction of movement, and number of intersection of the bicycle route with traffic roads. The tool uses the bicycle route drawn manually by designer in Rhino and provides visual feedback on the design actions. More specifically, it uses gradient colors from green to red to visualize the accessibility of the proposed route by bicycle. Potentially, it would be possible to categorize the routes by the required amount of individual physical effort by considering the weight of the bicyclist and the slope height relative to a starting point of a bicycle trip. 407

6 Christian Grewe-Rellmann, Hans Leidescher, Patrick Meier and Raymond Zahno. This work was supported by the SNF Grant of the National Research Program NRP 65 Sustainable Urban Patterns (SUPat). Also, we are very grateful to the reviewers for their valuable comments. Figure 8. The linkage between the two natural resources (river and the forest) (Leidescher) Figure 9. The resulting bicycle routes connecting the river and the forest (Leidescher) VIII. CONCLUSION AND FUTURE WORK In this paper we presented a method for parameterization of urban design qualities and the implementation of parameters in parametric and procedural software and demonstrated some results of the case study. The paper also provided an overview of the related work on the decision support tools for urban design. Since urban revitalization and enhancement of urban environment are likely to become significantly challenging tasks for urban planners in the coming decades, new design approaches are required. The presented method provides an example of combining the qualitative measurements of urban design qualities with interactive decision support tools in urban planning. For the evaluation of new urban qualities multiple city dimensions have to be considered. In the future work the ecological, socio-economic and design factors will be incorporated in the interdisciplinary design guidelines and additional set of parameters will be derived. ACKNOWLEDGEMENTS We would like to thank Jan Halatsch, Lukas Treyer, Tobias Wullschleger, Luis Gisler, Ulrike Wissen, Noemi Neuenschwander, Timo von Wirth and Julia Dyllong for their continuing support and for many helpful discussions as well as our students from the spring and fall semester 2011, who participate inside the workshop Articulating Urban Complexities and the major course New Methods in Urban Simulations at the ETH Zurich, especially Sebastian Hefti, REFERENCES [1] J.N. Beirão, J.P. Duarte, R. Stouffs. Grammars of Design and Grammars for Design: Grammar-based patterns for urban design, Joining Languages. In Cultures and Visions: CAAD Futures, PUM Canada [2] C. Derix. Smart Solutions for Spatial Planning, Digital Cities: London s Future. The Building Centre, London, 2009, Digital Masterplanning, In The Complete UrbanBUZZ, Jualiana O Rourke (ed), University College London Press, [3] DETR (Department of the Environment, Transport and the Regions). By Design, Urban design in the planning system: Towards better practice [4] J.S. Gero, Architectural Optimization A Review, In Engineering Optimization, Vol I, [5] R. Ewing, S.. Measuring the Unmeasurable: Urban Design Qualities Related to Walkability. In Journal of Urban Design, 14(1), [6] R. Ewing, T. Schmid, R. Killingsworth, A. Zlot, S. Raudenbush. Relationship between urban sprawl and physical activity, obesity, and morbidity. Am J Health Promot 2003, 18(1), [7] H. Frumkin, L. Frank, R. Jackson. Urban sprawl and public health: de-signing, planning, and building for healthy communities. Island Press [8] J.B. Kim, M.J. Clayton. Support Form-Based Codes with Building In-formation Modeling The Parametric Urban Model Case Study, ACADIA Conference Proceeding 2010s, [9] Jacobs A, Appleyard D, (1987). "Toward an Urban Design Manifesto", in Le Gates, R and Stout, Routledge. New York pp [10] C. Dee. Form and fabric in landscape architecture, UK, Spon Press [11] G. Cullen. The concise townscape. Butterworth-Heinemann, Burlington [12] J. Gehl. Life between the buildings. Copenhagen, The Danish Architectural press [13] R. Krier. Urban space, New York, Rizzoli [14] H. Loidl, S. Bernard. Opening Spaces, Basle, Birkhäuser [15] K. Lynch. The Image of the City, Cambridge, Mass., MIT Press [16] K. Lynch, G. Hack. Site Planning. Cambridge, Mass, MIT Press [17] J.O. Simonds, B. Starke. Landscape Architecture. New York, McGraw-Hill Professional [18] W.H. Whyte. The social life of small urban spaces. New York, Project for Public Spaces [19] J. Halatsch, A. Kunze, G. Schmitt. Using Shape Grammars for Master Planning. In J.S. Gero (ed), Design Computing and Cognition DCC 08, Springer, [20] A. Kunze, J. Halatsch, C. Vanegas, M. Maldaner Jacobi, B. Turkienicz,, G. Schmitt. A Conceptual Participatory Design 408

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