Reclaiming The Walkable City

For decades urban designers advocated more walkable cities without much success. Finally, in the past few years the quality of the walking environment has become an important issue in planning and design in the U.S.

Previously, transportation planners viewed movement by foot and bicycle as recreational, rather than legitimate transport to be seriously considered. A major shift in policy away from auto-centric planning, to mandated accommodation of the pedestrian and bicycle in federally supported transportation projects has stimulated numerous pedestrian and bicycle policies, plans, and built projects across the country. Recent studies on the many health benefits of walking have helped strengthen the case for making walkable cities.

Urban Design, Transportation Planning, and the Pedestrian

Urban design and transportation planning have evolved along distinctly different tracks over the past century, urban design focusing on the concrete experiential qualities of the built environment, generally at small to medium scale, and transportation planning focusing on more abstract function and efficiency for the motorist, at the scale of cities and regions. Before the “scientific” revolution in transportation planning, civil engineers in the U.S. were trained to deal with the character of the locale. The road was engineered to serve transportation needs, but also to fit in with the landscape and to enhance the experience of the user.

Beginning in the 1930s the profession of street and road design split in two separate directions: those who specialized in the technical aspects of transportation planning and engineering, and those who dealt with place-based design. While transportation planners have focused on abstract “macro” variables like capacity, demand, rate of flow, trip origin/destination analysis, congestion patterns, and regional land use patterns, urban designers and landscape architects have looked at “micro” variables, the form and use of local places. The consequences of this split for pedestrians and the built environment have been enormous.

Walkable Cities of the Past

Walkability was essential in cities before the automobile era. Streets of the preindustrial city were by necessity walkable, since everyone depended upon ready access by foot or slow moving cart, wagon, or carriage for access to jobs and the marketplace. Activity patterns had to be fine grained, density of dwellings had to be relatively high, and everything had to be connected by a continuous pedestrian path network. Cities of the middle ages were remarkable in their walkability and typically packed all the necessities of urban living into an area no more than ½ mile from the central square. For example, the entire built-up area of Urbino, Italy occupied only 300 acres yet housed 30,000 people. Early American cities like Boston were highly walkable, as well. Before major land filling operations began in the early nineteenth century, everything was on a small peninsula of little more than 800 acres where every point could be reached in a walk of less than one mile or ½ hour. Despite enormous growth and modernization, the central area still maintains its walkability, a rare situation for the American city.

High speed transport and the quest for efficiency killed the walkable city. Each advance in transportation technology — from horse drawn cart or carriage, to horsedrawn streetcar, to electric streetcar, to automobile and superhighway — has degraded the pedestrian environment. Hazardous high speed traffic broke up the fine grained pedestrian network and imposed barriers to free movement on foot. In ignoring the pedestrian experience, the street lost its intimate scale and transparency, and became a mere service road, devoid of public life. Modernist planning and design separated pedestrians from the automobile, shunting them off to raised plazas, skywalks, barren “greenways,” and sterile pedestrian malls. The automobile oriented values of Modernism have been codified in the transportation and street design standards that we struggle with today.

In the late postindustrial city it is impossible for the pedestrian or bicyclist to navigate freely. The street patterns of most residential areas built after 1950 are based on the discontinuous cul-de-sac rather than the interconnected grid. Block sizes are too large to permit a range of route choices and land use patterns are coarse with activities widely spaced and segregated by type. Streets are often over scaled and inhospitable to pedestrians and frequently lack sidewalks in order to reduce infrastructure construction and maintenance costs. The entire system has been designed for the convenience of the motorist (Southworth and Ben-Joseph 2003).

Why Walk?

The benefits of increasing walking are now recognized. Walkability is the foundation for the sustainable city; without it, meaningful resource conservation will not be possible. Like bicycling, walking is a “green” mode of transport that not only reduces congestion, but also has low environmental impact, conserving energy without air and noise pollution. It can be more than a purely utilitarian mode of travel for trips to work, school, or shopping, and can have both social and recreational value. It is also a socially equitable mode of transport that is available to a majority of the population, across classes, including children and seniors.

Compared with Europeans, Americans walk very little. Only 9 percent of total trips in the U.S. were by foot in 1990 but 84 percent were by car, whereas in Sweden 39 percent were by foot and 36 percent were by car. In The Netherlands and Germany walking and bicycle trips increase with age and account for over half the trips for people age 75 and older (Pucher and Dijkstra, 2003). In addition, only 6 percent of trips were by foot for Americans age 75 and older in 2000. (Frank et al 2003).

Walking can promote mental and physical health including cardio-vascular fitness, reduced stress, stronger bones, weight control, and mental alertness and creativity. Walking is the most accessible and affordable way to get exercise. As obesity has now become a major public health problem in the U.S., several studies have made connections between health and the design and planning of cities. They make a strong case for better design and planning of the pedestrian environment.

Three quarters of U.S. adults do not get enough physical activity, and one quarter is inactive in their free time. Nearly two thirds (64.5 percent) of U.S. adults are overweight and almost one third are obese according to a recent National Health and Nutrition Examination Survey (Ewing et al 2003). In contrast, European countries with the highest rates of walking and bicycling have less obesity, diabetes, and hypertension than the U.S. (Pucher and Dykstra 2003).
As little as ½ hour moderate activity such as walking or bicycling may be adequate for long term health, but only one quarter of the population achieves this (Frank et al 2003; Powell et al 2003).
People who live in “sprawl” are likely to walk less, weigh more, and have greater incidence of hypertension than people living in more compact areas (Ewing et al 2003). Residents of more walkable San Diego neighborhoods engaged in 70 more minutes of physical activity in the previous week and had less obesity; 60 percent of residents in less walkable neighborhoods were overweight (Saelens et al 2003).
Women between the ages of 70 and 81 who did more walking and other physical activity tended to have better cognitive function and less cognitive decline than those with less activity. Those with the highest levels of physical activity had 20 per cent lower risk of cognitive impairment (Weuve et al 2004). Men over 71 who walked the least (less than ¼ mile per day) had nearly twice (1.8 times) the risk of developing dementia as those who walked the most (Abbott et al 2004).
People who live in walkable neighborhoods may have higher levels of “social capital,” and are more likely to know their neighbors, participate politically, trust others, and be socially engaged (Leyden 2003).

Criteria for the Walkable City

“Walkability” might be defined as the extent to which the built environment supports and encourages walking by providing for pedestrian comfort and safety, connecting people with varied destinations within a reasonable amount of time and effort, and offering visual interest in journeys throughout the network.

What are the qualities of a walkable city? To encourage walking designers and planners need to go beyond utilitarian access and address several qualities of the path network.

1. The path network should be well connected without major gaps or barriers, both locally and in the larger urban setting. Connectivity of the path network is determined by the presence of sidewalks and other pedestrian paths and by the degree of path continuity and absence of significant barriers. While it is tempting for simplicity to measure walking distance to destinations radially “as the crow flies,” this approach can be misleading, especially when street patterns are coarse and fragmented. However, as patterns become finer grained and more interconnected, blocks become smaller with higher connectivity of paths, and the ratio of access for the “crow fly” measure to actual walking distance approaches 1:1.

In addition to path distances to various points, it is important to examine the amount of path choice. Density of path intersections and block sizes can be revealing: a high density of intersections and small block sizes usually correlates with a high degree of connectivity. Barriers to pedestrian access such as cul-de-sacs and dead end streets, or busy arterials, railroad or power line rights-of-way, rivers, or topographic features must be minimized.

Connectivity is best addressed when an area is being designed, of course, and is much more difficult to remedy once a place is built. Most of the post-industrial suburban landscape suffers from lack of pedestrian connectivity, typically with a pattern of disconnected cul-de-sacs and barrier arterials and highways. In some cases, connectivity retrofits might be possible, with pedestrian overpasses or underpasses across barriers, or traffic calming devices. Cul-de-sacs might be connected to provide a continuous bicycle and pedestrian system (Southworth and Ben-Joseph 2004).

2. Pedestrian paths should be linked seamlessly, without interruptions and hazards, with other modes such as bus, streetcar, subway, or train, minimizing automobile dependence. Walking and bicycling are now seen as essential ingredients in an integrated, intermodal transportation system to give travelers transportation options and to provide continuity from home to destination. Beyond providing an internally well-connected pedestrian network, it is important to provide connectivity with the larger city and region through convenient and accessible links to other modes such as bus, streetcar, subway, or train within a reasonable time-distance. This means that stations need to be spaced frequently enough to allow pedestrian access for residential and commercial zones, usually ¼ to ½ mile, or a 10 to 20 minute walk. A complete pedestrian network will offer full connectivity between all modes so that one can navigate seamlesslessly from foot to trolley or subway to train or air without difficult breaks. A small pedestrian district, no matter how well designed, cannot contribute to a reduction in automobile use if it is not well supported by transit and situated within an accessible mix of land uses.

3. Land use patterns need to be fine grained and varied, especially for local serving uses, so that pedestrians can actually walk to useful destinations. Studies have indicated that distance to destinations is the single factor that most affects whether or not people decide to walk or to take the car, and is more of a determinant than weather, physical difficulty, safety or fear of crime (Funihashi 1985; Handy 1996; Komanoff and Roelofs 1993). Several studies have found that the distance Americans will walk for typical daily trips is quite limited, ranging from 400 feet to about ¼ mile (Weinstein1996). Untermann found that 70 percent of Americans would walk 500 feet for daily errands and that 40 percent would walk 1/5 mile; only 10 percent would walk ½ mile (Untermann 1984).

A walkable neighborhood or city has an accessible pattern of activities to serve daily needs. This means that one can reach most local-serving uses on foot within 10 to 20 minutes or up to ½ mile. The types of activities that fall within this “neighborhood access” category include shops, cafes, banks, laundries, grocery stores, service stations, day care centers, fitness centers, elementary schools, libraries, and parks. However, most post-industrial development in the U.S. has lost walkability and the necessary fine-grained pattern of uses so that it is impossible in many areas to reach even one everyday activity on foot within ½ mile.

Could a very low density city ever become walkable? Land use intensity and diversity, like connectivity of the path network, are best established at the very beginning of the development process. Once a low density coarse grained pattern is put in place, it is a legal and physical challenge to insert density and variety.

4. The pedestrian network needs to be safe for people of varied ages and degrees of mobility, both from traffic hazards and crime. Perhaps the best understood and most fully developed aspect of walkability is pedestrian safety. In most U.S. cities transportation and land use policies have made walking and bicycling inconvenient, unpleasant, and dangerous. Each year 6000 pedestrians and bicyclists are killed in traffic in the U.S.; pedestrians are 23 times more likely to get killed than automobile passengers (Federal Highway Administration 2003). Environments that maximize fast and efficient auto travel are rarely enjoyable or safe for pedestrians and bicyclists.

A recent trend across the country has been “traffic calming,” techniques for making streets more pedestrian friendly by slowing down traffic through a variety of devices: chokers, chicanes, speed bumps, raised crosswalks, narrowed streets, rough paving, traffic diverters, roundabouts, landscaping, and other means.

5. Pedestrian paths need to be well designed in terms of width, paving, landscaping, signing, and lighting. The quality of the path itself, of course, is essential to walkability. Perhaps the least hospitable pedestrian path is the auto oriented commercial strip, a treeless expanse dominated by several lanes of noisy traffic, polluted air, glaring lights and raucous signs. The street has few, if any, designated crosswalks and is much too wide for a pedestrian to cross comfortably. The chaotic frontage is poorly defined, lined by blank big boxes, large parking lots, and drive-in businesses. Haphazard utility poles and boxes, street lights, traffic control signs, hydrants, mail boxes and parking meters dominate the sidewalk, which is constantly interrupted by driveways to businesses (Southworth and Lynch 1974).

If the strip is pedestrian hell, then the ideal pedestrian path will provide for the comfort and safety of pedestrians of varied ages and physical abilities. It should be continuous, without gaps, and should have a relatively smooth surface without pits, bumps, or other irregularities that could make walking and wheelchair access difficult. It should be at least wide enough for 2-3 people to pass one another or to walk together in groups, and much wider in very urban situations. Terrain can be a significant factor in walkability, especially in cities with snow and ice. Encroachments into the pedestrian right-of-way such as utility poles, mail boxes, or newspaper vending machines can compromise walkability by constricting the pathway or blocking crossings. Landscape elements such as planted verges help insulate the pedestrian from the moving traffic, and street trees provide protection from the sun and help define the street space. Pedestrian scaled path lighting can enhance nighttime walking and provide a greater sense of safety.

6. The path context, including street design, architecture and landscape, needs to offer visual interest and overall explorability. Perhaps the most problematic and least developed of walkability criteria are those related to quality of the path context. A safe, continuous path network in a monotonous physical setting will not invite pedestrians. The path network must engage the interest of the user. Many aspects of the path context can contribute to a positive walking experience: visual interest of the built environment, design of the street as a whole, transparency of fronting structures, visible activity, views, lighting, and street trees and other landscape elements.

The postindustrial city has become an increasingly closed and hidden world as processes of production and marketing are hidden from view. Big box shopping, introverted shopping malls and office parks, vast parking lots and reliance on electronic communications have all contributed to urban landscapes that are difficult to read. A transparent environment allows one to sense the social and natural life of a place through first hand observation. Such qualities are impossible to deal with at the macro scale of most transportation analysis and planning, but require detail design and attention to the special qualities of places. In most large developments of mass produced housing, repetitive architecture and uniform street designs devoted to the automobile have produced neighborhoods with little pedestrian appeal.

In the past century a few notable exceptions to the general trend of post war development have sought ways of maintaining pedestrian access, while accommodating the automobile. In the 1920s and 30s, Clarence Stein structured his designs for new garden suburbs such as Greendale, Wisconsin and Radburn in Fairlawn, New Jersey around a continuous green core with pedestrian and bicycle paths that connected homes with school, local shops, and transit. In Britain in the 1960s, Gordon Cullen and others developed plans to restore or reinvent the traditional townscape as an engaging “sequence of revelations” for the pedestrian (Cullen 1961). The idea is still alive, although not commonly seen, in places like Village Homes in Davis, California and Reston, Virginia. Many New Urbanist developments emphasize walkability, as well. In The Kentlands in Gaithersburg, Maryland particular design attention was given to creating pedestrian scaled streets with varied architecture and landscape. Small-scale detail along the streets, as well as changing vistas and focal points from neighborhood to neighborhood make it an enjoyable place to go for a walk. Every district has numerous alternate pathways. It has been so successful in this regard that people drive to it from other suburbs just to take a walk (Southworth, 1996). In all of these cases walkability has been an important feature, but regrettably each of the developments is a rather small, auto dependent island stranded in motopia.

There is no general theory of spatial design for the pedestrian environment that applies everywhere. Although many urban designers have attempted to develop formulas for street width, setbacks, or ratios of enclosure height to street width, for every rule that is made, examples of successful streets can be found that break the rule. The canyon streets of Manhattan are often perceived as attractive and walkable, as are the small seventeenth century lanes of Marblehead, or the broad tree-canopied boulevards of the Country Club district of Kansas City. Street trees and other vegetation almost always enhance walkability, but several European examples immediately come to mind that violate this ideal such as the treeless, arcaded streets of Bologna or the stone streets of Venice, Florence and Sienna. Here the architecture, street space, and street life provide the interest and engage the pedestrian in exploration. Many U.S. neighborhoods such as streetcar suburbs built from the 1880s to 1920s are rather nondescript architecturally, but still have a high degree of walkability. They are valued for the comfortable scale of the streets and blocks, the canopy of street trees, the variety of architectural expressions, and the connection of buildings to the street.

Successful approaches will vary by culture, place, and city size. Nevertheless, a few attributes are likely to contribute to the quality of path context in most urban and suburban settings: scale of street space, presence of street trees and other landscape elements, views, visible activity and transparency, scale and coherence of built form. The important thing is to engage the pedestrian’s interest along the route.

Conclusion

It will not be easy to achieve walkable cities in the U.S., especially since more than half of the typical American metropolis has been built according to automobile dominated standards. There may be resistance to improving things for the pedestrian or bicyclist, fearing space will have to be taken away from the car. Often it is more difficult to retrofit built-up areas because the patterns are already established. While it is not impossible to retrofit existing street networks to serve pedestrians and to insert some density and mixed uses into low density cities, it will require imagination and persistence.

To create the walkable city in the automobile age, emphasis will need to shift from almost total auto orientation, to acceptance and promotion of pedestrian and bicycle access at all levels. The regulatory environment will need to shift toward encouragement of walkability, and the design and planning professions will need to work toward creation of integrated pedestrian access at all scales of movement. The tasks are challenging but the benefits for urban life will be substantial. A focus on the walkable city will transform the way we live in fundamental ways, benefiting health, social relations, and the natural environment.

Acknowledgments

I am grateful for the assistance provided by Raymond Isaacs, Sungjin Park, and Jeff Williams.

For a more detailed discussion of this subject see: Southworth, Michael, “Designing the Walkable City,” Journal of Urban Planning and Development, Fall 2005.

References

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Frank, L., Engelke, P., and Schmid, T. (2003). Health and community design: The impact of the built environment on physical activity, Island Press, Washington, D.C.

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The Future of Infill Housing in California: Opportunities, Potential, Constraints, and Demand Infill

Infill: Pro and Con

Infill is the new urban development approach that isn’t new. City planners, designers, and urban policy officials have been trying to encourage central city development in various forms since the early 1940s. Federal involvement in this issue dates from the passage of the Housing Act of 1949 which authorized federal funding for urban renewal.

Conceptually at least, the fit between infill housing development and smart growth is a natural one as each additional housing unit built in a central city or older suburban neighborhood reduces the demand for housing at the urban edge. Indeed, while smart growth’s attempts to contain sprawl at the urban edge have met with resistance from developers, homebuyers, and many suburban officials, everybody, it seems, likes infill housing.

And they should. Infill housing makes three types of policy sense. As noted above, encouraging additional infill development reduces development pressures on outlying farmland, open space, and habitat lands. Second, encouraging additional infill development, particularly near transit lines and in neighborhoods that are currently or potentially “walkable,” may help slow the inevitable increase in automobile travel both on freeways and local roads. Third, and perhaps most important, many older neighborhoods are in dire need of new investment. Some of these neighborhoods are demographically and economically stable, but are suffering from years of inattention and underinvestment. Other neighborhoods, such as those of new immigrant populations, have become focal points of demographic and economic flux. Regardless of the particular situation, the increased private investment that is at the core of infill housing development can provide the additional financial and human resources that these communities will increasingly require.

As appealing as infill development may be in theory, it can be less appealing in practice. Done without good planning — that is, when not linked to appropriate infrastructure development and public service improvements — additional infill development becomes a formula for increased local traffic congestion, over-crowded schools and parks, and buildings that disrespect the history and character of existing neighborhoods. Done too quickly and without adequate safeguards, additional infill becomes a formula for gentrification, as existing residents are displaced to make way for new homes they can afford to neither buy nor rent. Done without reference to a viable financial model and the needs of private developers to earn reasonable rates of return, infill becomes simply a pipedream.

The California Context

Nowhere is enthusiasm for infill greater than in California, where state officials and legislators, regional agencies, local governments, organizations, environmental groups, and even homebuilders have all jumped aboard the infill bandwagon. Its reputation as the world capital of sprawl notwithstanding, California has already done a credible job accommodating infill development, particularly within its coastal cities and counties. Depending on how infill is counted, and based on an analysis of census data, infill housing accounted for between 20% and 35% of new homes built in California during the 1990s. Among counties, infill accounted for more than 40% of new housing units constructed in San Francisco, Yolo, Los Angeles, Santa Clara, Merced, Orange, Stanislaus, and San Mateo during the 1990s.

With California growing at a rate of five million people per decade, even more needs to be done. Recognizing this need, in 2004 the California Business, Transportation, and Housing Agency, and two of its departments — Caltrans and the California Department of Housing and Community Development — commissioned UC Berkeley’s Institute of Urban and Regional Development to prepare the first-ever statewide assessment of infill housing potential. Undertaken by DCRP graduate students Guangyu Li, Michael Reilly, Thomas Rogers, and Charles Warren, under the direction of DCRP professor John Landis and IURD Community Partnerships director Heather Hood, the assessment includes a statewide, parcel-based inventory of potential infill sites; an estimate of the sites’ potential to accommodate additional housing in appropriate locations and densities; current constraints preventing the development of infill housing; and an estimate of the current and projected demand for infill housing. In addition, results will be made directly available to local planners, redevelopment officials, elected officials, and developers via the internet.

Inventorying Infill Parcels

Because inventorying infill sites on a parcel-by-parcel basis is infeasible at the scale of a state or metropolitan area, this study makes use of county assessors’ records to identify vacant and refill (previously developed) parcels. Following the definition commonly used by county tax assessors, a vacant parcel is defined as one that has no inhabitable structure or building, or is currently not in use for extractive purposes such as mining or oil drilling. Parcels with structures too small to be inhabited, or for which the structure value is less than $5,000 (measured in constant 2004 dollars) are also deemed to be vacant. Refill parcels, also known as redevelopable parcels, are privately-owned, previously-developed parcels with a structure valued at $5,000 or more, but for which the improvement-value-to-land value (I/L) ratio is less than 1.0 for commercial and multifamily properties; and less than 0.5 for single-family properties. County tax assessors estimate improvement values and land values whenever a property is sold based on transaction values as reported to county deed recorders.

Whether a parcel should be counted as a potential urban infill site depends in part on where it is located as well as its availability for development or redevelopment. Using detailed Census data and digital maps, researchers delineated three sets of geographical “catchment” areas for identifying potential infill sites: Largest Infill Counting Areas (LICAs, having an average gross residential density of 2.4 dwelling units per acre), Middle Infill Counting Areas (MICAs, with a gross residential density greater than 2.4 dwelling units per acre and commercial and industrial areas within the urban footprint), and Smallest Infill Counting Areas (SICAs, with gross residential densities greater than 4 units per acre and potentially “walkable” — that is, their housing densities are high enough that a significant number of potential trip destinations are within an easy-walking distance of a quarter-mile).

Based on this inventorying method and additional exclusion conditions, California’s cities and urban neighborhoods encompass nearly 500,000 potential infill parcels comprising 220,000 acres of land. These totals were calculated by counting up all vacant and underutilized parcels within the state’s Largest Infill Counting Areas (LICAs). Moving from the Largest to the Middle Infill Counting Areas (MICAs) reduces the total number of potential infill parcels by about 10 percent and the amount of infill acreage by about 28 percent. Further restricting the set of potential infill sites to the Smallest Infill Counting Areas (SICAs) reduces the statewide number of vacant and refill parcels to about 345,000, and the amount of potential infill land area to approximately 84,000 acres.

Most potential infill sites in California are refill sites — that is, they are currently developed. Refill parcels account for 89 percent of potential infill sites within the LICAs, 92 percent of potential infill sites within the MICAs, and 95 percent of potential infill parcels within the SICAs. In terms of land area, refill parcels account for 71 percent of potential LICA infill acreage, 83 percent of potential MICA infill acreage, and 91 percent of potential SICA infill acreage.

Most potential infill sites are also small. The average LICA refill parcel is just 4/10ths of an acre in size; the average SICA refill parcel is but 2/10ths of an acre. Vacant infill sites are a bit larger, but barely so: the average LICA vacant parcel is just over an acre in size while the average SICA vacant parcel is 4/10ths of an acre. Some smaller parcels may be appropriate for lot consolidation, but this cannot be determined from assessors’ parcel data.

The largest share of refill acreage is currently in multi-family residential use. Multifamily residential uses account for 29 percent of LICA refill acreage and 44 percent of SICA infill acreage. Single-family homes account for another 13 and 22 percent, respectively, of LICA and SICA infill acreage. Turning to underutilized industrial sites — which have their own unique problems as potential housing refill sites because of the possibility of toxic contamination and a lack of residential services — only 11 percent of LICA infill acreage and 4 percent of SICA infill acreage consist of this property type. Although much has been made of the possibility of recycling older commercial buildings and shopping centers into new housing, only 6 percent of LICA infill acreage and 8 percent of SICA infill acreage is currently in commercial use.

Before considering how many housing units California’s infill inventory might accommodate, it is important to reiterate that all these estimates are based on an analysis of assessors’ parcel data, and not on individual site inspections. The quality of assessors’ parcel data varies by county, with land and structure assessments based on older transactions being particularly problematic. Of greater significance, we have no information regarding which, if any, of the parcels identified in the infill inventory are or might ever be made available by their current owners for sale and/or development. Indeed, the current lack of development activity in many infill neighborhoods that are otherwise ripe for redevelopment suggests that many owners of potentially developable sites do not see them as such.

California’s Infill Housing Potential

Based on the concept of neighborhood-appropriate density which links potential infill densities to the availability of quality transit service and supportive neighborhood land uses; and irrespective of physical, economic, and community feasibility issues, California could accommodate as many as four million additional infill units within its Largest Infill Counting Areas (LICAs). This is equivalent to twenty years of housing production based on a statewide production level of 200,000 units per year. About three million of these four million new homes would be constructed on previously developed sites in the form of refill. Another one million units would be constructed on currently vacant sites. Limiting infill housing development to California’s Middle Infill Counting Areas (MICAs) reduces the state’s estimated infill housing potential to about 3.6 million potential units. Further limiting it to California’s Smallest Infill Counting Areas (SICAs) would reduce the state’s estimated infill housing potential to about 2.1 million potential housing units.

Among refill housing units, the largest share could be built on parcels currently in residential use. Twenty percent of California’s LICA infill housing potential is associated with multi-family properties. If nothing else, this percentage indicates the vulnerability of the state’s multi-family neighborhoods to possible gentrification. Industrial sites comprise the next largest source of potential refill units.

By itself, Greater Los Angeles accounts for sixty to seventy percent of California’s infill housing potential. Based on its superior transit service and positive land use mix, the Greater Los Angeles Region could accommodate an additional 2.3 million infill housing units within its LICAs, an additional 2.2 million infill units within its MICAs, and an additional 1.5 million infill units within its SICAs. Most of this new housing development would occur in Los Angeles County. Elsewhere in Southern California, San Diego County could accommodate an additional 220,000 infill housing units in its SICAs and 422,000 in its LICAs. The infill potential of the San Francisco Bay Area, although sizeable, is far less than that of the Greater Los Angeles Region. Altogether, we estimate that the nine-county San Francisco Bay Area could accommodate between 360,000 and 752,000 infill housing units at average densities ranging from 37 units per acre down to 21 units per acre.

Much has been made of the potential contributions of transit-accessible development toward meeting California’s future housing needs, and this attention is merited. Statewide, it is estimated that upwards of 550,000 additional infill units could be accommodated on potential infill sites within walking distance (1/3 of a mile or less) of existing rail transit stations. This includes commuter systems such as Los Angeles’s MetroLink or the Bay Area’s Caltrain, subway systems such as BART or the Red Line in Los Angeles, and light-rail systems such as the San Diego Trolley or Santa Clara County’s VTA system.

Turning from rail transit to bus transit, there are more than 25,600 acres of potential infill land in California that are within a quarter-mile’s distance of a bus line offering high-frequency service. Altogether, we estimate these sites could potentially accommodate nearly 1.1 million infill housing units. As exceptional as this total sounds, most of it is in just one county — Los Angeles. The Los Angeles County Metropolitan Transportation Authority has been a national leader in the implementation of high-frequency bus service, including bus rapid transit, and approximately 900,000 potential infill units — almost half of all potential infill units in Los Angeles County — could be constructed on potential infill sites that are within a quarter mile of one of MTA’s high-frequency bus lines.

Barriers to Infill Housing Development

These estimates assume that every potential infill parcel that could be developed as infill housing would be developed as infill housing. This is unrealistic. Would-be infill housing developers face numerous difficulties and constraints — among them physical and financial feasibility. Physically speaking, larger lots are easier to develop than smaller ones. The attendant regulatory and parking challenges developers face in designing marketable housing on lots less than 2,500 square feet become so great as to render the lot almost un-buildable. Not until a lot is about 5,000 square feet in size — about 1/8^th of an acre — do the constraints to designing marketable infill projects begin to recede. Financially, the profitability of developing for-sale projects, while much greater than for rental projects, is insufficient to overcome the risks associated with the possibility of being sued for damages under current construction dispute concerns. A related constraint is the expense of infrastructure improvements — particularly schools, parks, and roadway capacity — necessary to accommodate additional development. Should the costs of upgrading local infrastructure and public services fall entirely on the subject property, they would likely render its development economically infeasible. Additionally, development on brownfield sites often entails remediation that is only discovered after construction has begun.

Other potential barriers include pre-emption and community character issues. Many of the identified sites carry current zoning designations that would not permit residential uses. Assuming these sites were reserved for future economic development, and therefore pre-empted from redevelopment into residential use, California’s infill housing potential would fall by about one million units. Redevelopment of parcels already occupied by apartment buildings — about thirty percent of the state’s infill inventory — runs the risk of displacing hundreds of thousands of low-income families. In addition, infill development, like any new development, has the potential to alter the character of existing communities. Even when individual projects pay attention to issues of community character and context, the cumulative effect of many such developments on a neighborhood or community may be considerable — especially when many changes occur over a short period of time.

Who is Moving to Infill Neighborhoods?

Taking a line from the 1989 movie, Field of Dreams, when it comes to infill housing, planners and developers alike seem to believe that “if you build it, they will come.” History cautions otherwise. While a number of central cities around the country — notably Chicago, Seattle, Houston and Atlanta — have successfully attracted significant numbers of new residents to downtown neighborhoods, this is still the exception; metropolitan decentralization continues to be the dominant residential development pattern. Compared to the market for suburban housing, the market for infill housing remains relatively small. But, like California itself, the infill market is growing and as the state’s population grows ever more diverse, the market for infill housing is also likely to grow.

A marketing axiom states that the best way to understand a prospective market is to study the current one. Rather than studying who is currently living in infill neighborhoods — defined in this study as central city neighborhoods and older suburban communities — we focus on who is choosing to move to those neighborhoods, and why. Recent movers are identified in the 2000 Census as those who changed location between 1996 and 2000.

Race and Ethnicity: Compared along race and ethnicity lines, California’s central city neighborhoods were far less attractive to white movers than its suburban ones. Based on the 2000 Census, white households comprised 46% and 61% of recent movers to older and newer suburban communities, but only 35% of recent movers to central city neighborhoods. The situation was exactly the opposite for Latino households, who comprised 35% of recent movers to central city neighborhoods and 28% of recent mover households to older suburban communities, but only 22% of recent movers to newer suburban communities. African-American households favored central cities even more than Latinos: 14% of recent movers to central city neighborhoods were African-American, versus 8% of recent movers to older suburban communities, and 6% of recent movers to newer suburban communities. Asian-American households, by contrast, tend to favor central city neighborhoods and older suburban neighborhoods (14% and 13%, respectively) more than newer suburban neighborhoods, where only 6% of recent movers where Asian-American. Not surprisingly, these percentages vary significantly by region.

Should these trends continue, many of California’s older central city neighborhoods will become more Latino in character, while the state’s newer suburban communities will continue to remain predominantly white. Between these extremes, California’s older suburban neighborhoods will continue to grow ever more diverse.

Household Type: Married-couple families, both with and without children continue to favor newer communities over older ones. Statewide, married-couple families with children accounted for 31% of recent movers to older suburban communities and 37% of movers to newer suburban communities, but only 21% of recent movers to central city neighborhoods. Mover households consisting of married couples without children favored suburban locations in similar proportions. Mover households who were separated, divorced, or widowed were equally distributed among the three neighborhood types, accounting for 12% of recent movers to central cities, older suburbs, and newer suburbs. Single-parent families followed a similar pattern, accounting for 11% of recent mover households to each of the three neighborhood types. Singles and non-traditional, multiple-family households, by contrast, continue to significantly favor central city locations over others. These percentages vary only slightly by region.

Should these trends continue, California’s central cities will become home to ever more singles and non-traditional multiple-family households, and fewer married-couple families. Newer suburban communities, by contrast, will be more oriented toward families — albeit many different types of families — while older suburban neighborhoods will be a melting pot for all household types.

Age: Following the family trends profiled above, younger movers tend to favor central city neighborhoods over suburban ones, albeit only slightly. On the other side of the age distribution, middle-aged and senior mover households continue to prefer suburban locations, particularly newer suburbs. This is not to say that empty-nesters — middle-aged couples whose children have left home — are not moving to central city neighborhoods; they are, along with older and newer suburban neighborhoods as well. These trends do not vary much by region. Should they continue, California’s central city areas will grow slightly, although perceptibly, younger over time, while its newer communities will grow perceptibly older.

Household Income: Central city neighborhoods are increasingly losing out to newer suburban communities in terms of resident incomes. Nearly half of California households who moved to central city neighborhoods between 1995 and 2000 earned less than $40,000 in 1999. By contrast, only a quarter of recent movers to suburban communities had household incomes less than $40,000. Among wealthier households, only 12% of recent movers to central city neighborhoods had household incomes above $100,000. In comparison, 20% of recent mover households to newer suburban communities had household incomes above $100,000. As with other demographic characteristics, older suburban communities fell in between, attracting a mix of households with diverse incomes. These findings do not vary much by region.

The Future Demand for Infill Living

Applying the recent mover demographic cross-section from the 2000 Census to the California Department of Finance’s 2010 and 2020 population projections suggests that the number of households living in California’s central city neighborhoods across the state will grow by 2% between 2000 and 2010 (rising from 4.4 to 4.5 million), and by 3% between 2000 and 2020, rising to a total of 4.6 million in 2020. The growth in central city households will be concentrated in a limited number of counties, notably Los Angeles, San Diego, and San Francisco counties, and to lesser extent in Santa Clara, Sacramento, and Sonoma counties. In a number of other counties, most notably Alameda, Contra Costa and Orange counties, the number of households living in central city neighborhoods may actually decline. Indeed, except for San Francisco, there is no California county in which the share of households living in central city neighborhoods will grow. Still, the past should never be regarded as automatically predictive of the future. Should a wider range of housing types and products be offered in central city neighborhoods than in the past — particularly housing of interest to families — it is possible that the demand for central city living could grow by more than these amounts.

The bulk of the increased demand for infill living will be concentrated in California’s older suburban communities. The number of households living in the state’s older suburban cities (e.g., Glendale, Pasadena, Torrance, Van Nuys, Fullerton, Santa Ana, and Chula Vista in Southern California; Berkeley, Fremont, Richmond, Sunnyvale, and Vallejo in the Bay Area) is projected to increase by 26% between 2000 and 2010 (rising from 2.7 to 3.4 million) and by 56% between 2000 and 2020, rising to a total of 4.2 million in 2020. Much of this increase will be driven by growth in the number of Latino households, who, if present trends continue, will favor older suburban communities offering inexpensive, single-family housing. Among the counties likely to see the largest population and household growth in older suburban communities are Los Angeles, San Diego, Alameda, Santa Clara, Orange, and Contra Costa. In the absence of policies and programs to encourage new construction to accommodate this growth, California’s older suburban communities will likely become much more over-crowded. The strong future demand for housing in the state’s older communities will also put upward pressures on land and housing prices.

Matching Infill Demand with Infill Potential: Quantitative and Qualitative Dimensions

It is now time to try to reconcile potential infill supply and possible infill demand. This will be done in two ways. The first is quantitative: it compares projections of the demand for infill living with the number of potential infill housing units. The second way is more qualitative: it compares the attributes sought by the types of households interested in infill living with the availability of those attributes in different locations.

Starting with the quantitative approach, there are six California counties in which infill housing potential greatly exceeds projected demand: Los Angeles, San Diego, San Bernardino, San Joaquin, San Francisco and Riverside. Los Angeles, San Diego and San Francisco counties are similar in that they couple a large numerical demand for infill living, a large supply of potential infill sites, and available transit and public services capable of supporting higher densities. Riverside and San Bernardino counties are different: their infill potential and development densities are low by regional and state standards, but their demographic demand for infill housing is lower still.

Counties in which infill potential and demand are in rough balance include Alameda, Santa Barbara, Kern, Santa Cruz, Marin, Tulare, Monterey, Stanislaus, San Luis Obispo, San Mateo, Sonoma, and Solano.

There are three counties — Contra Costa, Orange, and Sacramento — in which infill demand far exceeds infill potential. In Sacramento’s case, the demand for infill housing is reasonably strong, but potential infill sites are few and far between. Infill sites abound in Orange County, but they are outstripped by strong demand.

Just as the methods used to estimate infill potential and infill demand must be carefully scrutinized for their accuracy and applicability, so too must these last efforts to balance potential with demand. Infill developers face numerous difficulties, and the cumulative effects of these constraints increase with the number of potential infill units. This is particularly true in Los Angeles and San Diego counties, where infill potential seems to so greatly exceed demand. On the other side of the coin, some of the households counted as infill demand in Orange, Sacramento, and Contra Costa counties — the three counties where numerical demand exceeds potential — could just as easily choose to buy or rent a home in a newer suburban community. This would have the effect of reducing infill demand, and evening the balance between potential and demand.

These last caveats notwithstanding, this analysis suggests that, quantitatively at least, there is likely to be a sizeable market for infill housing in many of the same counties in which there is a large potential to build infill housing. This is good news for households seeking housing, good news for infill builders and developers, good news for planners and environmentalists concerned with smart growth, and good news for community leaders seeking to revitalize older neighborhoods.

The second match condition — the qualitative one — is more complicated. First, the good news: based on a detailed statistical analysis of recent mover preferences, no demographic group in any urban area was predisposed for or against higher densities. To the degree that they are offered the housing and neighborhood services they most value (at a reasonable cost), many households will happily consider living in a higher-density building or neighborhood. For builders, this means putting the emphasis on building quality, neighborhood quality, and product diversity, rather than on density. In a similar vein, except for Asian-Americans, no demographic group exhibited strong preferences for greater employment accessibility. This suggests that the market for infill living extends far beyond downtown commercial cores. On the flipside, all demographic groups had strong aversions to living in or near industrial zones. This suggests that isolated infill projects located in the heart of active industrial districts are likely to find it tough going, at least until they establish a critical mass of related activities. Finally, except for single-person households, the market for infill living seems to be larger, broader, and stronger in older suburban neighborhoods than in central city neighborhoods. Given the large supply of infill sites in older suburban neighborhoods and their more favorable economics, this is good news. At the same time, opposition to infill development may be greater in older suburban neighborhoods than in central city ones.

Ten Policy Suggestions

Ten specific public policy suggestions and next steps for promoting increased infill housing construction emerged from this study.

Improve the amount and quality of available information on potential infill development opportunities.
Establish a permanent funding source for affordable housing to be used in part to develop and implement cost-effective programs to help low-income households displaced by new infill development.
Require cities and counties to specifically identify potential infill housing sites and infill programs and strategies as part of their housing elements.
Streamline the development entitlements process, and in particular, the California Environmental Quality Act (CEQA), to reduce the regulatory uncertainty associated with infill housing projects.
Create new sources of infrastructure and off-site improvement financing for infill projects.
Develop a comprehensive community education/engagement strategy to generate public support for infill development.
Undertake a comprehensive review of the effectiveness of national and state brownfield remediation and liability laws; and to identify potential reforms to state law as necessary.
Focus and expand existing mortgage financing programs for first-time homebuyers who purchase new homes in designated infill development areas.
Review the effectiveness of SB 800 and if necessary, update it to further reduce the stifling effects of potential exposure to construction dispute litigation on the construction of attached infill housing.
Establish a demonstration program linking infill development to expanded state funding for elementary and middle schools in infill neighborhoods.

The full set of policy suggestions and alternatives are elaborated in The Future of Infill Housing in California: Opportunities, Potential, Feasibility and Demand–Volume One, available from the Institute of Urban and Regional Development (510-642-4874 or iurd@berkeley.edu).

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