1. Walkable Neighborhood Systems
SHERMAN L. LEWIS AND KRIS ADHIKARI
ABSTRACT This essay defines walkable neighborhood systems, summarizes the negative impacts of suburbia on the
economy as a whole, and presents indirect pricing as a major cause of suburbia. The paper proposes several pricing
reforms and green mobility as solutions based on prices that reflect full costs. Several hypotheses are presented concerning
the performance of walkable neighborhood systems and the concept of an inflection point for the takeoff of non-auto
modes when density within a walkable area reaches economies of scale. It proposes research on old neighborhoods as a
way to quantify relationships in the absence of pricing reforms. The paper discusses building types and high rise, and how
at highest densities there may be diminishing returns. While it is natural for most scholars to study dominant land uses,
there is a need to understand better dense walking neighborhoods as solutions to the costs of suburbia and to enhance their
functioning to show a path to a sustainable future.
Introduction
N eighborhoods should achieve several complementary goals: affordability, sustainability,
mobility, health and safety, good design, and community. This essay focuses on walkable
neighborhood systems as an alternative to suburbia to better achieve those goals, particularly by
increasing non-auto mode share.
Walkability and Suburbia in America
Neighborhood systems began to change in the mid-1920s with the advent of the automobile, and
suburbia transformed most urban areas in the decades from World War II to the present (Jackson
1985). The remaking of the landscape was socially popular, economically profitable, and politically
sacrosanct. Not content with spreading across rural and wild landscapes, promotors of suburbia also
took on the old central cities, punching freeways through built-up areas and, with “urban renewal,”
erasing the social fabric of old neighborhoods without appreciation for their cultural values (Jacobs
1961).
The tidal wave did not sweep all before it, as the most robust transit and finest old neighborhoods
often chugged along as before, with ups and downs of decay and gentrification. Efforts to draw urban
limit lines, save great neighborhoods, and revive transit have had some success, promoted by such
groups as 1000 Friends of Oregon, Congress for the New Urbanism, Smart Growth America, Green-
belt Alliance, and Transform.
Many scholars have looked at density and related factors to explain mode share between auto and
non-auto modes. For example, Ewing and Cervero (2010) analyzed the literature and concluded that
population density was weakly associated with mode of travel once other variables, like block size,
mixed use, destinations within walking distance, and transit availability were considered. By contrast,
Sherman L. Lewis is a Professor Emeritus of Political Science, California State University East Bay, Hayward, Hay-
ward, CA 94542, USA. His e-mail address is: sherman@csuhayward.us. Kris Adhikari has in BA, City and Regional
Planning, University of California, Berkeley, USA.
Submitted July 2016; revised August 2016; accepted August 2016.
VC 2016 Wiley Periodicals, Inc
Growth and Change DOI: 10.1111/grow.12185
Vol. 00 No. 00 (Month 2016), pp. 00–00

2. Holtzclaw et al. (2002) and Holtzclaw (1991) found a strong correlation between density and mode.
Unlike Ewing and Cervero, who surveyed a large number of articles, the Holtzclaw research included
a very dense neighborhood, northeast San Francisco, which was more likely to support walking, and
a very dispersed neighborhood, which was not. The research had high quality data on vehicle miles
traveled using odometer readings from smog tests and home addresses of car owners.
Another concern has been subsidies to single family housing and auto use as a driving force
behind residential dispersion and greenhouse gases, as well as having many external costs (Litman
2009; Tamminen 2006). Similarly, research has been done on neighborhood metabolism—inflows of
water, energy, and materials; outflows of wastes—but without specific attention to high density
neighborhoods (Codoban and Kennedy 2008)
These various concerns do not focus adequately on the underlying systems of land use, transporta-
tion, and pricing for livability and sustainability. The literature on density does not cover specific
high density neighborhoods with over 50 people per neighborhood acre. The Walkability Index mea-
sures places for how many destinations can be reached by walking but not the conditions that create
high walk access. The literature on pricing does not get into what would happen to urban form with
pricing reform reflecting all costs, including external costs. The discussion of neighborhood metabo-
lism does not consider underlying system. There is a need for more systematic attention to the sus-
tainability and livability of dense neighborhoods, not just as an alternative to suburbia, but as a better
way of life if properly understood and managed.
Walkable. . .Neighborhood. . .Systems
Walkability is defined here as the ability to make routine trips in an acceptable travel time without
having to park a personal car next to the home and without having to routinely drive long distances.
Walkability does not mean not using a car; it may include non-routine use of a car, car share, and car
rental. Walkability narrowly defined just means the attractiveness of walking and accessibility by
walking, and is not necessarily supported by an underlying system.
A neighborhood, by way of exclusion, is not most of the area of a country, the areas with little if
any housing—large natural areas, farming areas, large institutions like universities and hospitals,
industrial areas, and central business districts. Neighborhoods are not waterways or freeways,
not cemeteries or vacant land. These uses are generally outside neighborhoods, often helping define
their boundaries and edges. By way of inclusion, neighborhoods are the housing and nearby land
uses that serve them, primarily local businesses meeting routine needs, elementary schools, and small
parks.
Neighborhoods can be understood as systems of land use and transportation. Neighborhood sys-
tems range from rural to high density, from using mostly cars to using mostly walk and transit, and
from single family houses to high rise buildings.
A walkable neighborhood system is a neighborhood within attractive walking distances and suffi-
cient density to support businesses meeting routine needs and to justify frequent transit. The system
achieves economies of scale for walking and transit so that most trips are by non-auto modes. In
such systems, walking is the dominant mode within the neighborhood, and transit, car share, and ride
services (taxis, ehail, such as Uber or Lyft) dominate trips leaving the neighborhood. Autos in the
neighborhood are managed to not impede the functioning of the system. Such systems are located in
urban areas with transit to central areas.
Density in this essay means persons per neighborhood acre, i.e., lots plus streets plus local serving
land uses. Other ways of measuring density are based on lots, lots plus streets, and square miles
2 GROWTH AND CHANGE, MONTH 2016

3. including many non-neighborhood uses. Also, density here means density of persons, rather than
households or dwelling units, to avoid variations in household size and housing occupancy and ensure
greater per person accuracy. Neighborhood density is best measured per acre rather than per square
mile because walkable neighborhoods, to have attractive walking distances, are smaller than a square
mile.
Density is based on the area used for routine walking. Most statistics on density use official
boundaries, “official density.” Official density is easy to estimate and is useful for auto-based systems
where distances do not matter much. To get a better idea of the density as experienced by residents,
“functional density” is estimated by eliminating the peripheral areas not used for routine walking.
The smaller area better measures the relationships among usual walking distances, area, and density.
Non-neighborhood land uses, like a non-neighborhood business or institution, within the usual walk-
ing area must be included in the functional area because they make walking distance longer. The
common walking area is the one that counts for functional density.
Density and Other Things
Density is the most important variable because it determines the combination of walking distances
and economic demand for business and transit from residents within walking distances. Density is
important for itself and because dense areas almost always have walkable street patterns. Other
things—green mobility, parking, and building type—influence the functionality of the density.
Green mobility is a number of policies and their integrated application to help density to compete
with suburbia and the personal automobile while still providing a vehicle for personal use when
needed. Green mobility can increase non-auto mode share within the constraints of the density.
Green mobility does not work at low densities because walk distances are too long, but above some
density threshold it can have a significant impact on mode shift.
Green mobility has many possible policies: closeness to high quality urban transit, unbundling of
parking, neighborhood parking management, employee cash out, market parking charges, traffic
calming, safe and attractive pedestrian street crossings, car share, car rental, ride services, travel
vouchers for ride services for health care, rapid bus shuttles, ecopass and other pass systems, land-
based finance of shuttles, short corridor densification linked to rapid bus, phased development to find
the market for less parking demand, deparking incentives, mobility education, and mobility services.
Parking is a major component of green mobility; it is so important it merits separate consideration.
Parking and its related traffic in most dense neighborhood today generally has a negative impact on
non-auto modes by taking up space, hindering transit and pedestrians, and creating a safety hazard.
Density is achieved by residential buildings, and there is a correlation of density with building
types, which can be characterized as low rise, mid-rise, and high rise. In practice, density is achieved
by mixes of building types.
Low-rise buildings of one to two stories include single family detached houses which cannot
alone achieve much density even on small lots and narrow streets. Two story multi-plexes and row
houses can support a streetcar system but the density is likely to fall short for a walking density.
Streetcar systems fall between walkable systems and suburbia, with intermediate levels of density
and non-auto modes. Areas with predominantly low-rise buildings have low densities, generally not
reaching 40 persons per acre. Mid-rise, three to seven stories, seems to lend itself to walking densi-
ties. Areas of mid-rise buildings can reach densities of 40–100 persons per acre. A well-designed
neighborhood with three-story construction on walking streets can achieve a density in the 90–100
person per acre range. A high rise, eight stories on up, probably has more than enough density;
WALKABLE NEIGHBORHOOD SYSTEMS 3

4. clustered high-rise buildings can achieve over 100 persons per acre. High rise raises the issue of den-
sity becoming too high. In general, high rise is expensive to build, inefficient for energy, and costly
to maintain. High rise is often affordable only for people with high incomes or, if subsidized, for
lower incomes. Outside of central business districts (CBDs), high rise has disamenities, such as loss
of views of open sky, shadows, privacy, and loss of human scale.
Most modern high rise has additional issues of structured and bundled parking, which increase car
trips, and blank walls facing the street, detracting from walkability. Bundled parking functions the
same way as parking next to a suburban house, creating a kind of multi-story suburbia. By contrast,
despite other problems, a high-rise building with little or no parking and with stores on the street can
help walkability by increasing business demand and transit ridership, producing pedestrians instead
of traffic, having residents who walk and are part of the neighborhood, and having a pedestrian-
friendly street.
Economic Environmentalism: The Whole Economy and Suburbia
The “whole economy” includes both the money economy and the economy of non-monetized values
that are important but not easily quantified. The money economy has the advantage of self-
quantification but ignores the issue of value, while whole economy analysis quantifies by using esti-
mates, requiring research and judgment.
“Suburbia” refers to neighborhood systems with densities below about 40 persons per acre
and having auto dependency. Auto dependency means generally that over half of household trips
are made by car. Usually, cars are a virtual necessity. Suburbia has cars parked next to housing
and many miles of routine driving. In terms of the whole economy, the impacts of suburbia on
the habitability of the planet—its climate, its landscapes, its biodiversity—and on people—pollu-
tion, health, safety—have been extensive and severe. Suburbia has been a major cause of
human-made geologic change, creating the crisis of the Anthropocene. These impacts are briefly
described below.
Suburbia has caused the loss of millions of acres of natural land and working rural landscapes for
forestry, grazing, orchards, and crops. It has contributed to a loss of biodiversity in the greatest
extinction event since the emergence of Homo sapiens.
Suburbia uses more fossil fuel for housing and transportation than any other sector of the econo-
my. It is the major consumer of natural resources and consumes far more water than more compact
systems. Suburbia produces large quantities of waste from junked automobiles, batteries, tires, and
other auto parts. Suburban fossil use is the major cause of the greenhouse gases that have caused
global climate change, severe weather, and degradation of the oceans. Burning fossils causes air pol-
lution. Suburbia has spread things out, requiring cars for trips and making those trips longer. Even
when distances are short, drivers may circle around looking for parking.
Suburbia causes congestion, wasting time during peak hours despite the massive expansion of
roads. When cars intrude into denser areas, they slow each other down, as well as impeding transit
and pedestrians. Walking has become more difficult.
The tax burden often falls on non-drivers, as sales taxes replace declining revenues from gas taxes
and increased use of electric vehicles which pay no gas tax. The federal government has some subsi-
dies for oil companies and provides special tax breaks, lowering their share of taxes relative to other
industries.
Suburbia contributes to aesthetic degradation from visual blight created by wide arterials, parking
lots, lack of landscaping, overhead utility lines, and strip commercial signage.
4 GROWTH AND CHANGE, MONTH 2016

5. Suburbia has high health and safety costs. Auto dependency reduces walking, contributing to
deconditioning, over-weight, metabolic disorder and diabetes, and cardio-vascular disease. Cars are a
leading cause of property loss, injury, disability, and death. Auto deaths are the leading cause of
death among children and youth. Air pollution by particulates increases and aggravates asthma, espe-
cially among children in high pollution areas.
Suburbia has higher living costs than denser systems. Living costs combine housing, energy, and
transportation. In a denser system, non-auto modes can substitute for auto ownership. Higher housing
costs in cities are more than offset by lower utility and transportation costs, while suburban auto costs
are far more expensive than in the city (Benfield 2014). Even for low income people, living costs are
a higher percent of total income in suburbia.
Other social costs include reduced social diversity as neighborhoods segregate by income and get
further apart. Low income and disabled residents in suburbia often have limited mobility if they can-
not afford a car or cannot drive. Affluent people escape from neighborhoods with social problems,
which then become more concentrated and difficult to deal with. Suburbia reduces opportunity as
jobs move away from low-income job-seekers to suburban locations.
“Free” parking is one of the least recognized and most important causes of suburbia. As docu-
mented by Donald Shoup and other researchers, free parking has high costs (Shoup, 2014). In denser
areas especially, excess traffic preempts space from more efficient uses, slows transit, endangers
pedestrians, and aggravates congestion.
The annualized cost of a parking space in the U.S. is between $530 and $3,900 per year for land,
construction, and operation, excluding external costs. A typical construction cost of a single above
ground space is about $24,000 and of an underground space about $34,000 (Shoup 2014, 2016).
Underground parking in the CBD is over nine times as expensive as suburban on-street parking, but
even more expensive is on-street parking in the CBD because of land value (Litman 2012). The cost
of a structured parking space is usually higher than the value of the car parked there, so it would
save money to give cars away and charge for parking. Free parking causes a large part, about 20 per-
cent, of the energy use, pollution, and greenhouse gases from cars.
There are about four parking spaces per car, from parking by the house to parking lots for work,
shopping, and other purposes. Each auto uses 484 square feet of road space and 323 square feet for
parking. The equivalents for other modes are 0.11 square feet for walking, 1.1 square feet for
bicycles, 32.3 square feet for buses, and 1.29 square feet per passenger with 25 people on the bus
(Shoup 2014). Parking and roads per household take up more land area than the average house
(Litman 2014).
The combined costs of suburbia in the whole economy seem to outweigh the benefits while the
money economy shows the opposite. Yet these overall costs do not seem to intrude much into the
pleasant life of most people who live in suburbia.
Indirect Pricing and Pricing Reform
Indirect pricing as used here includes a wide range of concepts like non-monetized values, indirect
prices, subsidies, and external costs of autos and detached housing that make suburbia cheaper than
it would otherwise be. Each impact of suburbia discussed above has some kind of indirect pricing as
a cause. Todd Litman documents that external costs are about 35 percent of average car costs. (Lit-
man 2009) and there are several other ways of making similar estimates.
One of the most important and least recognized causes of suburbia is how indirect pricing pre-
vents responsible choice by consumers and reduces the productivity of the whole economy. Indirect
WALKABLE NEIGHBORHOOD SYSTEMS 5

6. pricing obscures and reduces the competitiveness of walkable neighborhoods and allows autos to
degrade their quality of life. Indirect pricing means the money economy does not serve the whole
economy.
U.S. cities and their neighborhoods were evolving in a relatively sustainable way into the 1920s,
based on walking and transit. Auto ownership took off in the 1910s without initially causing auto
dependency or changing land use. In the mid-1920s suburbia emerged, began to expand, and then
accelerated after 1945.
Indirect pricing for detached housing and personal transportation in the monetary economy has
heavily favored suburbia. Suburbia has not been significantly caused by greedy developers, bad plan-
ning, or the American car culture. The belief that people want suburbia ignores the choices they
would make if prices directly reflected real costs.
Yet little has been written on the influence of pricing on neighborhood systems. Most studies of
the whole economy have looked at nature services, climate change, carbon pricing, and other external
costs. Similarly, a large literature documents the many aspects of indirect pricing, but does not con-
sider them as a whole influencing neighborhood systems. Many articles that seem to be about neigh-
borhoods turn out to be about the neighborhood characteristics of survey respondents. Articles about
neighborhoods do not cover specific higher density neighborhoods.
Pricing reforms would reduce the role of the car to where it would pay its own way. Some issues,
such as road capacity and parking, affect neighborhoods more directly than others. Concerning road
capacity, Americans embrace the capacity model. They expect roads to be a public good paid for by
the general public rather than a private good paid for directly by users. When expansion of capacity
is not based on economic demand but on congestion created by free use, the result is more traffic
because the previous congestion was hiding latent demand—new users attracted by a faster trip.
Also, land use changes to increase traffic. More capacity brings cheap land within commuting dis-
tance, making subdivisions profitable. More subdivisions lead to more driving, more congestion, and
more capacity.
Another model, equally unsatisfactory, is the congestion model, which holds that congestion itself
is the best solution. It may waste time but it prevents induced demand from more capacity. This
model is used in older urban areas where land acquisition is so expensive it deters many road widen-
ings. Central congestion, however, helps push more suburbanization further out. Neither model has a
way to tell how much is enough. The solution, at least for market economists, is the pricing model:
build the capacity people are willing to pay for. Capacity would become more of a private good. The
gas tax is part of this model, as are congestion fees and parking charges.
Parking has special relevance for neighborhood systems. One pricing reform is market charges for
parking. Modern technology makes it easy to implement, eliminates circling for parking, and creates
more parking availability. Another reform is unbundling of parking space rent from living space rent,
which creates a significant incentive to not park a car on site, to not own a car, and to use non-auto
modes.
Pricing, which is used in most of the economy without a second thought, would provide the level
of parking and congestion that people are willing to pay for. More expensive auto costs would
increase the competitiveness of non-auto modes. People in rural, exurban, and suburban areas would
tend to move to denser areas, have less expensive and more efficient cars, and reduce the frequency
of trips. Pricing incentives would pull suburbia back toward the urban core and closer to anchor loca-
tions like employment and education. People would live closer to anchor destinations and use exist-
ing job-housing balances more efficiently by driving past each other less. Pricing reform would
encourage the restructuring of neighborhoods over time from less dense with low transit use to more
6 GROWTH AND CHANGE, MONTH 2016

7. dense with more transit use. Reform would help revive transit where it worked historically in central
cities and in streetcar systems, which tend to have the density and land use pattern needed for rider-
ship. Pricing reform would increase the competitiveness of walkable systems and evolve neighbor-
hoods toward more walkability, economic efficiency, and a higher quality of life. Sustainable
urbanism would resume.
How far all of this would go toward streetcar suburbs and walkable systems is hard to say, but the
process would be determined by honest prices to benefit the whole economy.
Hypotheses
Walkable neighborhood systems can provide mobility more productively for the whole economy
than suburbia. A walkable system generally works better with more people to support more business
and transit. Densities with fewer than 40 persons per acre do not get non-auto mode share above half
of trips. There is an inflection point or tipping point of neighborhood density for the take-off of non-
car modes, where economies of scale of the denser system take hold, and use of non-car modes
increases faster than the density. The density range for takeoff may be in the range of 40–50 people
per acre. Similarly, at the high end of density, there may be a tapering off range above 100 persons
per acre where the costs of density begin to outweigh the advantages. Green mobility, especially
parking policy, can increase non-auto mode share to the extent density allows. Mid-rise buildings
achieve the medium densities that support walkability. Pricing reform would favor walkable neigh-
borhood systems and benefit the whole economy.
Policy and Old Walkable Neighborhoods
The car culture so dominates American politics at this time that only limited implementation of
pricing reform is possible. More progress may be possible from studying old walkable neighbor-
hoods and effecting better policies to improve their functioning.
Data from the San Francisco Bay Area give an impression of the big picture. This large area data
is a useful framework for later zeroing in on specific neighborhood systems. Using some reasonable
cutoff points, the Bay Area in 2000 had rural neighborhoods which averaged 0.1 people per acre,
exurban at 1.1 people, and suburban, 6.4 people. Central city neighborhoods averaged 21 people per
acre, and the urban core had 47 per acre. See Table 1. This typology can be applied to all modern cit-
ies and can use varying cutoff points.
San Francisco is typical of metro areas in having a tiny percent of area at a high density yet hav-
ing a percent of metro population all out of proportion to the area. The data quantify just how much
land suburbia consumes relative to higher density. The urban core has 30 times as many people as its
area, while suburbia has 4 times as many.
Three Major Density Levels for Research
Coming down to the neighborhood level, the three major densities for research are: 1) less dense
areas that cannot achieve a walkable system, 2) a middle density that can, and 3) very high density.
Densities below 40 persons per acre define low density and correspond to the rural, exurban, subur-
ban, and some central city of Table 1. Densities from 40 to 100 persons per acre define medium den-
sity and correspond to the rest of central city and much of the urban core. Densities above 100
persons per acre are high density and at the high end of the urban core.
Some preliminary concepts of walk distances and area can frame what to look for on the ground.
To ensure decent walkability, the maximum walk distance from edge to center or major transit stop
WALKABLE NEIGHBORHOOD SYSTEMS 7

8. should not be over 0.75 miles, or 15 minutes. Similarly, the neighborhood area should not be over
about 320 acres. A hypothetical neighborhood that size could be a half mile wide and a mile long with
a central street across the middle of the mile dimension. The longest walk to the center line would be
half a mile. With 50 persons per acre the population would be 16,000, more than what is needed to
support a grocery store, a drug store, eating places, and a few more local serving businesses.
A methodology for defining real neighborhoods, still being developed, uses census block popula-
tions shown in choropleth (showing density by color of each block) by density ranges on an ArcGIS
map. A buffer zone a half mile wide can be drawn along major transit routes. Blocks within the buff-
er showing higher densities can be defined as neighborhoods. The ArcGIS table can be exported to
Excel and analyzed with other neighborhoods.
The research leads to a database of neighborhoods, their geographic block identifications numbers,
populations, official areas, functional areas, official densities, and functional densities. If the function-
al area is smaller than the official area, it will have a higher density. To look for the inflection or tip-
ping point, the middle densities from 40 to 100 persons per acre can be further stratified. The
neighborhoods can be ranked by functional density and grouped into density ranges of 10 persons
per acre—40–50, 50–60, and so forth. The database ranges become the basis for looking for correla-
tions of density with local business and transit and mode shift as density increases.
System and Variation
Real neighborhoods are diverse, each distinctive in some way, but with underlying similarities as
systems. Internally, neighborhoods have blocks with lumpy shapes and varying densities without
affecting neighborhood functionality. Neighborhood boundaries are unlikely to precisely enclose
actual use by walking residents, and walking patterns themselves are likely to have fuzzy boundaries.
Some neighborhoods stand out with clear boundaries while others are contiguous with adjacent
areas along a major arterial or transit line. Neighborhoods can vary from bigger neighborhoods with
higher density and more mixed use built around a rapid transit station, to smaller neighborhoods with
limited business and buses to a nearby central area with rapid transit.
TABLE 1. DENSITY OF LAND USE IN THE SAN FRANCISCO BAY AREA.
Persons
per square
mile
Square
miles
Percent
of
region
Population Percent
of
region
Persons
per acre
1 Rural <500 5,569 80.5% 369,523 5.5% 0.1
2 Exurban 500–1,000 305 4.4% 222,584 3.3% 1.1
3 Suburbia 1,000–10,000 397 13.0% 3,647,552 53.8% 6.4
4 Central City 10,000–20,000 119 1.7% 1,596,294 23.5% 20.9
5 Urban Core >20,000 32 0.5% 947,807 14.0% 46.9
Region 6,923 100.0% 6,783,760 100.0% 1.5
About 2000 Census, 4,422 block groups, 9 county Bay Area.
Bay Area Alliance for Sustainable Communities, Bay Area Indicators: Measuring Progress
Toward Sustainability, January 2003, p. 27, based on Metropolitan Transportation Commission,
ftp://ftp.abag.ca.gov/pub/mtc/census2000/PL94171: BlockGroup-shp -pldata.zip and related popu-
lation files for 4,422 census block groups.
8 GROWTH AND CHANGE, MONTH 2016

9. Comparable functionality can be achieved in a larger area with less density and longer walks,
or a smaller area with more density and shorter walks. Such trade-offs of area and density have
unknown relationships to performance. For example, at the larger end, about 250 acres with
10,000 people, which is 40 people per acre, could work well with supporting design. Similarly, a
smaller area of 20 acres and 2,000 people, which is 100 people per acre, could also achieve
walkability with a rapid shuttle to nearby business with an average trip time, walk plus wait plus
transit, within 15 minutes.
Where a neighborhood is close to a CBD, there could be demand in the neighborhood from non-
residents as well as residents. However, there may, in fact, be little mixing. Despite the closeness of
the CBD, local business is even closer for the residents so they probably would not generally go into
the CBD, and conversely the non-resident population has little reason to go into the neighborhood
for routine needs. If so, the neighborhood near the CBD still functions similarly to a more remote
neighborhood. The differences would be more of degree than system.
A problem of analysis begins as density declines and non-neighborhood uses increase. A neigh-
borhood may have enough density and walkability to be a walkable system, yet also may have land
uses for purposes such as employment, special shopping, or entertainment. The non-residents may
provide significant purchasing power that increases business above what residents alone could pro-
vide. On a smaller scale, a neighborhood place may become so popular that it draws in outside
patronage, particularly for restaurants, specialty shops, and street ambiance. Occasionally, a mega-
store or mall with big parking lots may have some housing nearby, where the neighborhood is too
small to support even a small store by itself, but can take advantage of the demand created by subur-
bia, so it has some walkability without the system.
Systems transition from suburbia to mixed to walkable. As densities increase, neighborhood sys-
tems change in terms of travel mode, travel times for non-auto modes, business and transit viability,
building footprints and height, floor areas ratios, and so on. During a transition phase, walk distances
may remain too long, and walk-based purchasing power and transit ridership may be too low to be
viable for a walking system, so auto trips may diminish but still prevail. The challenge is to find in
the complexity where density reaches the level where non-auto modes can prevail.
Characteristics of a Walkable Neighborhood System
The neighborhood would tend to have mostly narrow, quiet streets with slow or no traffic, which
foster social ties along blocks (Appleyard 1981). It would have small blocks for walking connectivi-
ty. Mid-rise buildings—mixed uses, apartments, condominiums, and town houses—with minimal set-
backs would achieve density with human scale aesthetics compared to high-rise buildings. There is
room for small parks and linear greenways while maintaining density. There would be a central street
or area with local business and convenient access by transit and even walking to the rest of the city.
Walking and transit would dominate mode share, supplemented by carshare/rental and taxi/ehail
rides. Fast, free, frequent transit to a CBD, and other major destinations would be well patronized.
The benefits of a walkable system parallel the costs of suburbia. The system is more sustainable;
it uses much less natural and working land, protects biodiversity, and reduces consumption of ener-
gy, resources, and water, and reduces waste. It cuts fossil use, greenhouse gases, and other pollution.
The system reduces trip distances, congestion, auto dependency, and externalities in dense areas
while improving walking and transit. Transit, with more riders and shorter distances, becomes cost-
effective. The transportation system becomes more clearly a public benefit worthy of tax support,
and the tax losses to the oil industry decline with the industry itself. Aesthetic degradation related to
WALKABLE NEIGHBORHOOD SYSTEMS 9

10. cars is dramatically reduced with less pavement. Safety improves from less car use, and health
improves from cleaner air and more walking. Living costs are substantially lower. The amount of
parking is reduced and is managed by unbundling, permit programs, and market-based parking fees.
There are lower rates of auto use and auto ownership. Driving a car for routine trips becomes difficult
and impractical due to congestion, cost, lack of affordable parking, and the relative advantage of
non-auto modes.
Future Research
Given the dominance of suburbia, most research, if it looks at high density at all, lumps all high
densities into one group, usually one of the smaller groups. A database on how dense neighborhood
systems achieve neighborhood goals is needed to test the various hypotheses.
Mode share. The database will need mode share data by neighborhood. This is challenging
because data are not available at the block level and census data only look a mode of access to work
for block groups. Some extrapolation from available data, or special access to databases respecting
confidentiality problem of small sample sizes, is needed. More difficult, surveys of persons using
travel diaries, GIS devices, and questionnaires about walking routes, neighborhood identity and so
on are needed to establish more exactly where non-auto modes can dominate mode share.
Very high density. Can the start of disamenities at the high end be identified? Research could
look for a lack of improvement in mode share and at energy consumption by residential buildings.
Research could look at social ties on a block, replicating Appleyard’s work (1981).
Building type. How does residential building type correlate with density? The U.S. census may
have data for small areas for single family detached, duplexes, row houses, three to five story build-
ings, and over five story buildings, or similar data. Statistics on distribution by neighborhood and by
neighborhoods within density ranges would indicate how building type changes with increasing den-
sity. Low density neighborhoods are likely to be dominated by single family detached houses and
have too few people for walkability. Above 100 persons per acre, high-rise may dominate. For poli-
cy, building type data could identify opportunities for densification.
Outlier neighborhoods. Green mobility and walkability are complex and hard to measure, so
one approach would be to look at outlier neighborhoods for more obvious factors affecting perfor-
mance. Within a density range, some individual neighborhoods are likely to perform especially poor-
ly or well on mode share. Outlier neighborhoods could be looked at for factors that cause anomalies.
For example, field research on walking routes could see if a high non-auto mode share had particular-
ly attractive paths, or a low non-auto mode share had hostile walk paths. Another suspect would be
parking. Abundant free parking would be expected to reduce non-auto modes, and limited and
charged parking to increase them.
Land use pattern. Generally, high-density neighborhoods have a supportive layout, putting
business and transit in the center and housing on the periphery. The pattern does vary, however, and
limited research indicates it can make a difference: Centrally located local businesses with transit
may allow non-auto modes of travel to serve a majority or more of trips (Crane et al. 2006).
There should be interplay between field research and modeling, to improve modeling from field
work and to improve policy using predictive modeling.
Field research. The neighborhood database will largely be based on census data and GIS maps
with some use of Google Maps 3D and Google Earth. Field research could easily establish the major
walking routes defining each neighborhood, and provide a reality check on what maps indicate. Inter-
views of residents could establish reasons for locational decisions and see how much those reasons
10 GROWTH AND CHANGE, MONTH 2016

11. can be achieved at higher housing density. Interviews could find out how people in walkable neigh-
borhoods use them for walking and transit and how they want the neighborhood improved.
People care about their neighborhoods. There is potential to involve neighbors in field
research, similar to the successful citizen science programs using home computers.
Modeling. Can trips in suburbia and in walkable neighborhood systems be modeled to show the
density level where non-auto modes begin to perform better? Could a model predict mode shift from
policy changes? The sophistication of urban models like UrbanSim and of transportation models like
activity-based models could be applied to high densities. Concepts of travel time budgets for routine
trip purposes could be used. Could an economic model based on the whole economy and pricing
reform show greater welfare? The California Air Resources Board and the California Strategic
Growth Council have models for estimating vehicle miles traveled, air pollution, and greenhouse gas-
es from small areas that could be used to compare the walking systems and suburbia (CAPCOA
2013).
Conclusion
Neighborhoods are systems of land use and transportation influenced by the pricing of housing
and transportation in the money economy. Indirect pricing has favored suburbia, which is failing in
the whole economy. Clearly, suburbia, across a wide range of criteria, has high costs, and a walkable
system will perform better. A walkable neighborhood system has sufficient density over a walkable
area to support businesses meeting routine needs and frequent cost-effective transit.
This approach brings a strong market-based perspective and concern with efficiency in the context
of the whole economy to include non-monetized values. Serious pricing reforms would favor an evo-
lution toward walkable systems of medium density, mid-rise buildings, and non-auto modes. Reform
could also support streetcar systems. Suburbia would shrink to the point where it paid its own way.
While pricing reforms make sense, cultural and political resistance makes for slow going.
Old dense neighborhoods provide a laboratory for quantifying mode share along a range of
increasing densities to find where economies of scale support a takeoff of non-auto modes. Similarly,
there seems likely to be a point of diminishing benefits at very high densities. A disciplined database
of neighborhoods is a first step toward an understanding of neighborhood systems and developing
policies.
The complexity of the urban mosaic makes it difficult to see underlying systems. A more quanti-
fied understanding of walkable neighborhood systems from modeling and study of old dense neigh-
borhoods could help develop policies to improve their performance.
Walkable neighborhood systems are a framework for research and policy for cities in the twenty-
first century. While most research seems to focus on the dominant suburban system, some focused
research should study a more promising path to a sustainable future. Walkable systems can achieve
the purposes of neighborhoods better than suburbia, providing comparable mobility, reduced costs,
and increased benefits. Development of walkable neighborhood systems would grow the whole econ-
omy and improve the quality of life.
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