140｜PracticeUrban development from parking lots
considering inner-city parking density
1. Background and goals
Automobiles are now a vital means of transportation for the elderly and persons with disabilities, to theextent that in rural parts of Japan, there are over 0.8 automobiles for person. Every automobile requires
around 15 m2 of parking space, both at the point of departure and at the destination; this is approximately the same amount of space per person in an average Japanese residence. As a consequence, parking spaces in many cities currently occupy approximately 20–30% of the inner-city surface area. In atypical planned city, parks occupy approximately 3% of the surface area and roads approximately 25%.
Accordingly, the area required for parking cannot be ignored in urban planning.

2. Research content
In this project, emphasis is placed on three “D”s and one “M.” The first “D” is “density”, which refers to
how many parking spaces are needed in inner cities. The second “D” is for “disposition,” which refers towhere parking lots should be placed. The third “D” is for “design,” which refers to specifically what kindof parking lots should be provided. The “M” in this study is “management”, which refers to how to manage parking lots. Each of these four aspects must be carefully considered. This paper presents an overview of research regarding density, the most fundamental of the four points described above.
2-1. Level of parking needed in urban areas
To investigate the required scale of parking lots needed in inner-city areas, we performed on-site investigations in Japan, the United States, United Kingdom and Germany (Fig. 1). We found that the cities
with the most parking spaces available were Houston and Dallas in the United States, which had over
200 spaces/ha. The locations with the least parking were central London and Westminster.
As for Japanese cities, downtown Yokohama, Shibuya, Yokosuka, Odawara, Shinjuku andTachikawa have approximately 50–70 spaces/ha. There were slightly more in Chiba, Kofu and Saga,
which had approximately 75–80 spaces/ha, and relatively new towns located some distance from Tokyo
such as Chiba New Town and Tsukuba New Town had around 100 spaces/ha, thanks to the numerous
large-scale parking facilities in those areas. Note that most locations have approximately 60–70
spaces/ha, which is thought to be because local government ordinances regarding parking spaces inJapan mandate a nearly identical level.
Project Leader: Takayuki Kishii
Professor, Department of Civil Engineering, College of Science and Technology, Nihon University

Urban development from parking lots considering inner-city parking density｜141250

United States
Germany
United KingdomThailandJapan
Japan (Kofu, Saga)

Parking density (spaces/ha)

200

212

216

156

150
120
110
97

100

48

50
30

53

59

60

60

60

67

68

73

73

75

76

78

80

33

20CentralLoW ndonestminsteSa ritamaShibu
Yo yakoham
Yo akosuk
Fra ankf
Ca urtmbridg
Od eawara
Shinjuk
Tauchikawa
DTa armmast
Ne adtw
Town
Ch
iba
Sag
Ike abukuroTsukub
KaNofu
Ch ew
Toiba
w
Nenw
TownPortl
andBang
kokDa
llas
Hous
ton0Figure 1. Parking density
Japan: Designated parking development districts;
USA: Inner-city business improvement districts; Europe: Inner loop areas(Locations that clearly seem to be privately owned garages are excluded)

2-2. Comparison of local government regulations regarding parking spaces
The primary reason for the situation in Japan is established by local government ordinances regarding
parking spaces. Table 1 shows an international comparison of similar local government regulations inother countries. Houston, which has the largest number of parking spaces, has established requirements
for a minimum number of available spaces. The parking requirements in downtown Houston are on parwith those of suburban shopping centers (around 200 spaces/ha), and furthermore specify that at least
75% of parking spaces should be provided on site, meaning that there are ample parking spaces even in
inner-city areas.
Among the areas studied, London has the fewest parking spaces. It places an upper limit on thenumber of parking spaces that can be created. On the other hand, Japan has established lower limits likeHouston, so while there is some variation between industrial and commercial areas, requirements generally mandate 30–60 spaces/ha. Other cities examined, such as Portland, Cambridge and Frankfurt,
have local government regulations regarding parking spaces that fall somewhere between those of
Houston and Japan.
2-3. Parking situation in overseas cities
Differences in the laws and standards of various countries have a strong effect on their parking circumstances. We therefore next compared two cities closely associated with this project and introduce theirmain features below.

142｜PracticeTable 1. Comparison of local government regulations pertaining to parking availability standards(offices, commercial)

Houston(At least 75% on site)

Portland(Core Area, converted as NFA = 0.6LowerlimitOffices
Commercial

269 spaces/ha
431–538 spaces/ha

Upper
limit

OfficesCommercial

75 spaces/ha
180–358 spaces/haUpperlimit

OfficesWithin CPZ
Commercial 100 spaces/ha + disabledparking
Disabled parking only

Outside CPZ
250 spaces/ha + disabled parking
200 spaces/ha

Upper
limit

OfficesCommercial

286 spaces/ha
333–666 spaces/haGFA)

Cambridge(Within the inner-city controlled
parking zone (CPZ))

Frankfurt (FF)(Inner city, 90% cash payment)

JapanLower
limit

30–60 spaces/haLondon

Upperlimit

7 spaces/ha

Houston, Texas
Houston is the fourth largest city in the United States. Most of its downtown is contained within a 2×2km area. Within that area are approximately 100,000 parking spaces, for a density of 216 spaces/ha. Thisis approximately the same level of parking service found in large-scale suburban retail stores. There are
90 multilevel parking garages with approximately 800 parking spaces each. There are also approximately
300 surface lots.
Portland, Oregon
Portland is a public transportation-oriented city with an approximately 2×1 km downtown area sandwiched between a river and an expressway. Similar to Houston, the streets in inner-city Portland are
generally in a grid pattern, as are streets in many American cities that were planned out during the pioneer days. As a result, roads alone account for approximately 40% of land use in the downtown area. The
average parking density is approximately 120 spaces/ha, a density far higher than that of Japan, despite
the city’s image as being highly oriented toward public transportation.

3. Conclusions
Looking at the parking situation of major cities in Japan and overseas, the density of parking spaces inhighly automobile-oriented societies is approximately 200 spaces/ha, but in cities with highly developed
public transportation a density of around 60 spaces/ha is sufficient. Between those extremes, public
transportation-oriented American cities and local cities in Japan seem to have around 90–120 spaces/ha.

Urban development from parking lots considering inner-city parking density｜143

However, effort is required to maintain the density at these levels, despite the fact that the results ofderiving a relational equation for standards of local government regulations regarding parking spaceand parking density show that insofar as standards are adhered to in local Japanese cities, this density ismaintained. This is because when parking space availability follows demand, the density soon increases
to 150 spaces/ha. In such cases, half of inner-city areas become devoted to parking and buildings consequently seem to exist in a sea of parking lots. Our hope is that this project will contribute to preventing
such an outcome through the development of attractive, functional urban spaces.

4. Future outlook
In the major cities of Japan, even when accounting for illegal parking, there is a surplus of inner-cityparking spaces. This indicates the need for a more flexible approach to local government regulations
regarding parking spaces (revising basic units, establishing mechanisms for utilization of parking spaces
in remote locations, providing alternative parking through cost-burden sharing, etc.) and proactive
aggregation of existing parking lots. We also believe there is a need to consider drastic changes to laws
pertaining to parking lots, such as by adding provisions that place upper limits on the number ofrequired on-site parking spaces. The handling of parking spaces has a large effect on inner-city land use
and thus will require greater attention in the future.