by Stefanos Polyzoides
Introduction: Lots, Blocks and Streets
Throughout human history, people have settled the land based on two fundamental desires, to be both in motion and in place. Cities as we understand them today were formed when the necessary movement of people and vehicles through them began to crystallize in the design of distinct rights of way. And as in response, in the enabling of stasis, human comfort and security, pleasure and production, in the form of distinct blocks, lots and buildings of various kinds.
The physical character and livability of human settlements has always existed in the intersection between the design and maintenance of this grid of potential, a simple binary system of Urbanism: blocks defining streets for mobility, streets defining blocks for inhabitation.
The particular design of these two key ingredients of city making has changed radically in pattern and scale over time, adapting to human needs. Their interdependence has not. We can experience it in all kinds of beloved existing traditional places: in Villages designed for hand cart service, in towns organized around the movement of animal drawn carriages, in cities built to the scale of motorized vehicles, in regions supported by transit.
1 Density and Mobility: The Link Between Development and Transit
Development related to transit is a 19th century phenomenon whose benefits we are beginning to rediscover. The new, expansive scale of mass production of the Industrial Revolution demanded greater concentrations of workers living within cities in order to service the labor needs of emerging businesses. The combined environmental effects of factory pollution and poorly designed housing associated with the densification of cities fueled an exodus of residential development to the suburbs. The scale of cities was forever transformed both by intensity and by distance.
Mass transit was born as humanity’s first response to the twin challenges of moving more people further than ever imagined or attempted before. The systems of choice were the streetcar and the railroad. The resultant urban forms were station-driven, the central business District (CBD) and the suburban town. There are many such places operating today, with admirable efficiency, architectural distinction, living quality and value-building force. Most of them are to be found in the metropolitan regions of New York, Philadelphia, Boston and Chicago.
The rediscovery of transit as a catalyst for development and redevelopment in the present is more than anything else, a response to the ravages of auto-based sprawl in the latter half of the 20th century.
Reclaiming cities, selectively densifying them, remixing their uses, recharging their economic ingredients, recasting their environmental performance, depends on introducing mobility strategies beyond the automobile. The choice of walking and taking transit, allows people to access their work place and various services foregoing the remarkable cost of owning and maintaining a car, and eliminating the catastrophic environmental effects associated with operating cars and car-generated growth.
2 TOD and DOT at the core of Sustainable Urbanism
There are two basic strategies for using transit as an agent of urbanization: Transit-Oriented Development and development-oriented transit.
The first strategy, TOD, was brilliantly utilized in the United States in the late 19th century and up to the 1930s for the purpose of opening up green field sites for development. Streetcar lines were constructed to gain access to the periphery of cities, and transit-accessible suburbs were built in almost every city in the United States. By the beginning of sprawl-based suburbanization in the 1950s almost every city in this country was organized around streetcar-centered arterial roads. Indeed, the definition of arterial road included a streetcar Corridor in its center. These streetcar systems were almost entirely demolished by 1965, as all growth became strictly and exclusively auto-oriented.
The second strategy, DOT, is currently being practiced to redevelop underutilized urban land or to intensify the building fabric in underperforming or under-serviced parts of cities. The catalytic effect of inserting transit into such areas can be substantial. Station sites and the Neighborhoods, District and Corridors surrounding them become accessible to metropolitan populations as living, working, retail and entertainment destinations. Their economic potential and physical form can be radically transformed.
TODs and DOTs are an important model of an alternative sustainable Urbanism, a key tool in the reconstruction of the American metropolis. Both strategies provide a development option that reverses auto-centric sprawl: Single family subdivisions and commercial strips isolated by immense arterial roads and over-dense, disconnected buildings and precincts surrounded by seas of cars.
3 Choosing a Route
The choice of a transit route is essential in determining both the viability of a transit system and the evolving character of the places it affects by the location of its stops.
On a regional scale, the introduction of streetcar systems strengthens the economic primacy of the city centers at their terminus, and the sub centers on every stop along the way.
In choosing a route and stops for Greenfield development, these must enable the greatest mixed-use housing opportunities. A terminus must also provide the maximum employment potential, attracting people to commute from the metropolitan edge to its center.
A route chosen for redevelopment should connect potential receiver and sender sites, established or planned places of intense urban activity, whether rich in just housing, or any combination of housing, employment, retail, entertainment or special uses. Each of these places around stops must have the potential to be further intensified and enriched by an appropriate further mix of uses that encourage pedestrian activity and transit ridership. An adequate street network and space for future parking facilities must be available to enable redevelopment on every station Neighborhood or District.
A redevelopment-based system must be similarly supported by a large concentration of housing and jobs at its terminus.
4 Station Types by Mode, Heavy Rail, Light Rail, Streetcar and Bus-Based
All transit-related development is organized around a quarter-mile pedestrian shed, and a half-mile bicycle-riding shed around stations.
Such development is possible around the stop of all modes of transit, heavy rail, light rail, streetcar and bus. The design of stations is particular to the technical requirements of each mode, as it is to the urban context within which it is introduced.
Within a development intensity transect from rural to urban, stations assume a particular design character depending on which transect zone, from T1 to T6, they are located within. Stations in suburban locations should be designed as free standing platforms, corresponding and reflecting the order of their urban setting. Similarly, stations in metropolitan downtown locations should be designed under buildings in subway configurations.
As stations are typically a vital part of the public realm, they should be prominently located and highly visible to the people trying to access them, or should be accessed through a coherent way-finding system. And they should be so designed as to support the idea that other buildings and their uses, including housing, can be located as physically close to them as possible.
5 Station Planning: Access and Parking
The most crucial dimension of station planning is the means by which people access a station to either board transit, or to get to a destination after having traveled by transit.
There are five ways to access a station, walking, by other forms of transit, by taxi or jitney, by being dropped off or picked up in a private vehicle, and by a private vehicle to or from parking. All of these have to be accommodated in the design of the right of way surrounding a station.
Essential to the performance of a station as an urban place is the design of the public realm surrounding it in a manner that favors pedestrian convenience and safety over vehicular speed. The larger and more prominent the station, the more it should be framed by appropriately sized plazas or parks that enhance the ease of pedestrian access.
Cars must be always removed from view in this public space surrounding stations. When designed into garages or lots, retail or work-live liner buildings should screen them. When designed into the underground garages of mixed-use buildings, they should be entered peripherally.
Retail and commercial activities can transform stations into destination draws, useful beyond their purpose as embarkation or arrival points. Pedestrian portals off parking garages or lots should be located more remotely, up to 750 feet away from the station entrance. Pedestrians walking from their parking to the station platforms can boost the performance of the retail businesses located along their way.
The less intense the development around a station, the more proximate the location of parking should be, in part to enhance a sense of security for transit riders during off peak travel.
6 Kinds of TOD/ DOTs by Place Character, T1 to T6
As in station design, buildings and places around them should correspond to a transect of development intensity from rural to urban. Buildings, open space, landscape and infrastructure should assume a particular character, depending on which transect zones they are located within.
Small, low-rise, detached, horizontal mixed-use buildings should be expected in lower intensity urban settings. Attached, mid-rise, mixed-use buildings and large, high-rise, vertical mixed-use buildings should be common in middle and high intensity urban locations respectively.
Within an urban fabric, the density of the particular buildings deployed should vary by the degree of their closeness to the transit station, the closer the station, the denser the building. Beyond the immediate surroundings of a station, and as its direct physical presence and influence wanes, urban and architectural design challenges become those associated with the design or redesign of any sustainable Neighborhood, District or Corridor: interconnectedness, public realm definition, compactness, diversity, efficiency:
Right of ways that are interconnected and multi modal; buildings that form the realm of public space of thoroughfares, parks and plazas by containing and hiding parking; projects and their uses that operate within a finite pedestrian accessibility shed; projects and their uses that are accommodated within a broad range of place, buildings and unit types, and infrastructure that is affordable, effective and green.
7 Neighborhood, District & Corridor Visioning
Whether in development or redevelopment, planning should encompass the entire Neighborhood, District or Corridor surrounding a station.
The physical changes brought about by the construction of new transit systems and the intensity of expected private development around them can be unsettling to the public. The transformation of existing conditions is immediate and intrusive. The benefits generated by this kind of intense change can seem distant.
Therefore, the construction of a transit system must always be linked through a community process, to a visioning urban design charrette. The community of neighbors living in proximity to stations can then discern the mobility, economic development and physical design benefits that a station design may produce for them.
Such a process should be transparent, participatory and engage all constituencies involved, especially a mix of public and private interests. Most typically, the product of such an effort should be a special area Master Plan.
Master Plans for Transit-Oriented Development must include at a minimum sections on a development strategy that is both economic and fiscal, a physical vision including catalytic or priority projects, a public infrastructure analysis and projection and an implementation framework that outlines public and private responsibilities for seeing a Master Plan through to fruition.
8 Neighborhood, District & Corridor Coding
Transit stations, particularly fixed rail stations, provide unique opportunities for durable urban development. Their permanent locations, guarantee that large numbers of riders will access them every day in perpetuity. It is not surprising, therefore, that they become places where housing and other uses can be assembled to serious economic and fiscal advantage. Transit-Oriented Development Master Plans typically establish the vision for such transit-centered Neighborhoods, Districts and Corridors. They are best implemented through the actions of many developers, their projects often including many and diverse buildings and public spaces.
Conventional urban growth is highly regulated. Yet, the current, dominant mode of Euclidean zoning is vague when it comes to managing the ongoing form of the City. It induces the kind of unpredictability that deters developers from investing in projects that promote collateral development in their vicinity. The tendency to produce one-off, oversized, metropolitan-scale projects follows. Isolated from and unresponsive to context, these are reflexive attempts by developers to gain some modicum of control over the quality and character of their projects, by sheer size accompanied by physical and economic isolation.
Form-Based Codes are the indispensable tool for seeding the alternative to mega projects: incrementally assembled ensembles of smaller buildings and the human scaled places between them. This method of coding offers predictability by establishing the building, open space, landscape, and right of way standards that deliver an orderly urban form, by many development interests, over time. They also regulate uses in a flexible manner that allows a fast response to changing economic patterns and space needs. As Form-Based Codes support phased, incremental design actions, they become ultimately supportive of both private and community interests. They maximize the performance of private projects, while building up a stable and permanent public realm.
Architectural design must follow upon Neighborhood or District Master Plans that include a vision and code for the station area. It is not politically viable to design in the context of TOD’s and have to fight planning and architectural battles simultaneously. The gross size and scale of expected projects must be clearly established in advance of any architectural design.
9 A Transit Proximate Architecture
Contrary to current common understandings of Architecture, style is not the essential building-scale design ingredient of Transit-Oriented Development. A space-first strategy is. New buildings that embrace station and train right of ways, and frame them into a coherent realm of defined public space are the appropriate response to the design of transit stop sites. This is particularly true in the case of light rail, where buildings should not shy away from being located as close to moving trains as possible.
Supporting absolute pedestrian connectivity shapes transit-proximate buildings in a variety of ways. The proper configuration of buildings and public space in station vicinities depends on reciprocal, people-friendly thoroughfare design. Street parking, drop-off lanes and slow-moving traffic generate large volumes of pedestrian traffic which positively affects both the character of buildings and the experience of living in them.
Most important, ground floors are essential ingredients of TOD project design. Buildings in a transit station context should be designed to accommodate a variety of uses over time. Their ground floors should be activated continuously, with commercial frontages predominating. If residential, ground floors should be open and accessible every twenty or so feet. Their parking should be placed behind and under them, and car entrances should be located discreetly, to also interfere as little as possible with the forming of pedestrian-dominant urban public space.
TOD projects should be fitted into existing contexts in a manner that validates the historical continuity of towns and cities. New buildings should be designed in conjunction with adjacent existing ones to generate thoroughfares and public space of distinct character. This can be most often accomplished by designing available entitlement programs into building types of various densities and combining them into site plans that accomplish both internal project coherence and a better fit into the collective form of a Neighborhood or District as a whole.
Most often, buildings of diverse types can also be designed to incorporate a variety of dwelling units by type and size, and can be expressed in an assortment of vernacular and contemporary styles. It is this complexity and variety, this attention to both the measured definition of new projects and the completion of existing street and city block form that generates an authentic sense of place. The broad consumer choice inherent in projects so designed is also a key ingredient to their financial success.
Notwithstanding issues of density, buildings should be designed in a manner that expresses their residential character. Their gross form should speak of human inhabitation. The fabric of such buildings should be made of materials and building components and assemblies that reflect a human scale and invite people to use them and experience them close up.
Designing for Sustainability at the building scale should capitalize on issues that are common practice in residential design, cross ventilation, natural lighting, highly insulated shells, locally available construction materials and low technologies. This emphasis on passive modes of environmental control reflects the importance of permanence and durability in Green Design. Architecture dependent on exotic construction techniques and expensive environmental control devices is not a preferred option for new housing projects. Buildings so endowed offer little incentive for developers to risk higher project construction costs, when the economic benefit of Sustainable Design accrues not to them, but their buyers.
10 Phasing & Implementation
The difference between the typified and commoditized production housing of sprawl and mixed-use urban housing is the rich mix of amenities that is typically associated with mature urban Neighborhoods. Housing developed around transit creates competitive advantages for the dwellings and supporting commercial uses that are proximate to it. This increased accessibility overcomes opportunity costs associated with congestion. In this manner, transit becomes an amenity that can catalyze rich development opportunities in the vicinity of stations, and can produce significant competitive economic premiums in the housing market.
Transit-Oriented Development is a process that should recognize the role of the station in the overall context of the regions’ economic structure. There is no standard recipe for transit-supportive development. As projects are defined, their programming should distinguish between destination versus origin uses in order to generate places, and by extension building and development strategies that are unique to the special economic profile of each station.
Joint development opportunities with transit or redevelopment agencies should be actively pursued. These may maximize public investment by offering land write-downs to private developers in order to stimulate development. Other opportunities to cooperate should also be followed through with the local authorities that have control over the entitlement and development processes. Changes in development standards, such as parking to building ratios or the establishment of a Park Once District, and increasing densities in the vicinity of stations, are prime examples of the benefits of public/ private partnership on transit-oriented projects.
Despite their clear dependence on public sector cooperation, these kinds of developments need to be solidly anchored in the logic of the Market. Their internal economics should be based on a realistic assessment of prevailing conditions in their setting at the time of their design and construction. In a mixed-use strategy, each use should be economically feasible, and able to be financed in its own right. Together, transit and a mix of uses should produce increasing returns on investment stemming from their synergy and the resulting physical and economic integration of the project as a whole.
Transit-oriented projects are typically large and complex enough to demand a multi phase development process. Such projects should be deployed on sites as large as possible. This in order to avoid isolated and incomplete improvements, and to produce the economic benefits expected of sequential project development.
Conclusion: Toward a Successional Urbanism
Architecture is the means by which change is incrementally managed in nature and the city today, and typically, in the service of social and economic betterment. This is perhaps the most potent force operating on both our natural and urban environment, and it becomes visible in two distinctly different forms:
As a chaotic process of assembling mobility and utility infrastructures, buildings, open space and landscape into uncoordinated and fragmented subdivisions; or as authentic, well-composed, well-constructed, well-managed whole places, incorporating the same set of urban design ingredients into harmonious Neighborhoods, Districts and Corridors.
Both of these twenty-first-century models lack the prospect of growing their foundation Urbanism into a more mature settlement. On the one hand, endless sprawl locks in the adolescent urban configurations of separate use zones, anemic choices of building types, enormous city blocks and inadequately connected, over-dimensioned thoroughfares. On the other, highly planned and controlled places are typically frozen into a legal, fiscal, economic and architectural fixity. The design pattern, under which both were first delivered, becomes permanent. This is what we experience almost everywhere in the world as random as opposed to intentional change.
A true Urbanism is one that encourages and delivers successive stages of urban development by horizontal extension or by vertical transformation, or both. There are many key factors that encourage growth from one transect intensity to the next. As population densities increase, as use mixes become more varied, as institutions proliferate and employment concentrations intensify, as the need for all kinds of services multiplies, the demand for convenient mobility skyrockets.
Parking scarcity and traffic congestion are the hallmarks of cities in this kind of transformation. Investing in transit and transit-related development become the keys to keeping cities in a growing mode, while their character is transformed from one stage of maturity and service to their inhabitants to the next.
First published in Banerjee, Loukaitou-Sideris: A Routledge Companion to Urban Design, Routledge, London, 2011