EVALUATION OF SPACE-TIME ACCESSIBILITYCONSIDERING ACTIVITY ENGAGEMENT OF THE
ELDERLY
Nobuaki OHMORI, Dr. Eng. and Noboru HARATA, Dr. Eng.
The University of Tokyo, JapanSUMMARY
Toward aged society, it is important to provide better mobility and accessibility for theelderly and disabled people, so that they can live their independent life in community.
This paper proposes methods for analyzing space-time accessibility of the elderly
people, in terms of activity participation under space-time constraints in their daily life
as one of the measures for evaluation of mobility-related social exclusion. Accessibility
to general hospitals in a local city is analyzed before and after relocation of a hospitalfrom city center to suburban area. The results suggest that after the relocation it isdifficult to maintain the present level of accessibility only by an improvement in public
transport services, but an improvement in opportunity side is useful for enhancing
space-time accessibility.

Introduction
Toward aged society, it is important to provide better mobility and accessibility for theelderly and disabled people, so that they can live their independent life in community.
The elderly have a wide range of constraints on participating in out-of-home activities;
for example, physical disadvantages, keeping regular lifestyle for their health andcustoms, limited space-time areas of activity engagement for both safety problems andlimited ability of information acquisition, and monetary budget constraint. In addition,
people who cannot drive a car depend more on public transport service and sometimes
need their household members’ help when they go out. Therefore, their choice sets offeasible activity patterns are strongly restricted by these constraints. Furthermore,
especially in local cities, motorization has been promoting relocation of large-scale
facilities (shopping centers, hospitals, etc.) to suburban areas, and the level of public
transport service has been decreasing. More often, the elderly with lower mobility face
the situations that they cannot participate in out-of-home activities as they wish. This isregarded as one of the mobility-related “social exclusion” problems. Kenyon et al.
(2002) defined mobility-related exclusion as “the process by which people areprevented from participating in the economic, political and social life of the community
because of reduced accessibility to opportunities, services and social networks, due inwhole or in part to insufficient mobility in a society and environment built around theassumption of high mobility.” From this viewpoint, it should be useful to analyze thefeasibility of activity participation of the elderly under personal and environmental
constraints they face in daily life.
On the other hand, the space-time prism constraint formalized by Hägerstrand (1970) is
a very useful idea for specifying alternative feasible activity-travel patterns inspace-time. Burns (1979) expanded the concept of accessibility into space-time
dimensions, “space-time accessibility,” introducing the activity duration at opportunities
based on the prism constraints. Lenntorp (1978) operationalized Hägerstrand’s approachby developing PESASP model that calculated the total number of space-time paths
given a specific activity program and the urban transport network. In recent studies,
Kwan (1998) and Miller (1999) operationalized space-time accessibility under the
space-time prism on a real world transport network using Geographic Information
Systems (GIS). These accessibility measures represent the potential of activity
participation under space-time constraints and could be useful to evaluate the extent ofmobility-related social exclusion.
The objective of this study is to propose methods for analyzing space-time accessibility
under space-time constraints of daily activity schedule, transport environment andactivity opportunities, as one of the measures for evaluation of mobility-related social
exclusion. Accessibility to general hospitals for the retired elderly living in a local city
is analyzed and the impacts of accessibility-enhancing policies are evaluated before andafter relocation of a hospital from city center to suburban area.

Methods for Analyzing Accessibility
A case study was conducted in Akita city, Japan. The population consists of about
318,000 and the ratio of people aged 65 years and over (the elderly) is 17.5%, from2000 census data. In near future, the ratio of the elderly of Akita prefecture is expected
to be the highest in Japan. Accessibility to general hospitals in the city was evaluated as
one of the important facilities for the elderly people’s daily life.
Three accessibility indices were defined in this study: travel time; generalized traveltime; and the feasibility of activity participation under space-time prism constraints
which is one of the space-time accessibility measures. Two travel modes, car and bus(or walk), were considered in the analyses. Data on population of the elderly atresidential zones (1×1 km2 mesh areas), road and bus networks, and location of general
hospitals with the attribute of opening (consultation) hours were prepared in GIS(MapInfo).
Travel time and generalized travel time
Travel time by car from each residential zone to the hospitals was assumed the travel
time traveling the route of the minimum travel time calculated on the road network.
Travel time by bus was assumed the travel time traveling the route of the minimum
generalized travel time calculated using equivalent coefficients, which change theamount of time of several travel modes in a trip to that of base mode (Nitta et al., 1995).
The following coefficients were used referring to the previous research (Shin, 1997):
boarding on bus 1.00; walking 2.38; transfer 5.26; and waiting 1.92. In this study, thegeneralized travel time is the time changed to boarding on bus mode.
Space-time accessibility: the feasibility of activity participation under space-time
constraints
Travel time and generalized travel time are basic measures of accessibility, but these
represent only the effort (or ease) of overcoming spatial separation. Essentially both
spatial and temporal components of accessibility, which represent potential ofparticipating in activities at opportunities, should be evaluated considering that travel isa derived demand from engaging in activities. As one of the space-time accessibility
measures, we analyzed the feasibility of participating in medical care activity consulting
doctors at general hospitals in space-time constraints, which is the most important
activity in the elderly people’s daily life. Data on the elderly people’s activity schedules
were required for determining their daily prisms.
The national time use survey in Japan (NHK Broadcasting Culture Research Institute,1996) reported that one of the characteristics of the elderly people’s activity patterns
was that day-to-day variability of their daily time use was smaller than that of younger
people’s. The results from the survey conducted by the authors in Akita in 1996 showedthat the elderly people, especially retired, kept the regularity of location and timing for
waking up, going to bed and having meals (Ohmori et al., 1999). Based on the evidence,
activities were classified into three types: Activity (a) is fixed activity (sleep, meals);
Activity (b) is planned but flexible activity (personal care, housework, etc.); andActivity (c) is discretionary activity (hobbies and entertainment, reading, TV watching,
except for Activities (a) and (b)). The feasibility of medical care activity participation in
hospitals was calculated according to the advanced space-time prism concept (seeOhmori et al., 1999; 2003a; and 2003b); that is s/he starts traveling after the end time ofan Activity (a), arrives at the hospital within consultation hours, spends time for waiting,consulting a doctor and getting some medicine, leaves the hospital and arrives at thelocation of the next Activity (a) in the start time of it.

Evaluation of Accessibility to Activities at General Hospitals
Travel time and generalized travel timeFirst, travel times and generalized travel times from each residential zone to 5 general
hospitals in Akita, by car and bus, were calculated. These measures were weighted by
the population of the elderly at each zone using census data and the average times in thewhole city were calculated. The results showed the difference of accessibility between
Table 1 Round-trip travel times and generalized travel times to the hospitals (minutes)
A
B
C
D
E
Average* Minimum**
Car
23
25
24
30
31
27
14
Travel time
Bus
62
82
73
86
100
80
55
Generalized
Bus
107
145
140
154
187
147
99
travel time
* The average of (generalized) travel times to the five hospitals** The average of the minimum (generalized) travel times from each zone to the fivehospitals

travel modes and among hospitals (see Table 1). Travel times by bus were about threetimes as large as those by car. Travel times by car to Hospital A, B and C were almost
the same, but the differences of travel times by bus between Hospital A, B and C wererelatively large. Generalized travel times by bus to Hospital B and C were larger thantravel time to Hospital A, because of longer egress walking time for Hospital B andlonger transfer time for Hospital C.
Space-time accessibility
It was assumed that daily activity schedules of the retired elderly depended on age andsex groups. For each 4 segment group, young (aged 65–75 years) men, young women,
old (over 75 years) men and old women, a set of activity schedules were created from71 retired elderly people’s activity diary and the evidence of the fixity of timing andlocation of some activities from the survey data conducted by the authors (Ohmori et al.,1999). The retired elderly of 4 segment groups in each 226 zone in the study area were
supposed to have the same set of activity schedules as the sample.
Table 2 shows the consultation hours of department of internal medicine in the fivegeneral hospitals. Outpatients were required to arrive at the hospital within these hours.
They were supposed to travel by car or bus from their residential zone to hospitals.
Activity duration including waiting and consultation at the hospital was set at 120
minutes based on the activity diary and the national time use survey results. Figure 1
Table 2 Consultation hours of the hospitals
Hospital A Hospital B Hospital C Hospital D Hospital E
In the morning 7:00–11:30 7:00–11:30 8:30–11:30 8:30–10:30 7:00–11:30
In the afternoon—
12:00–16:00——
12:00–15:00
Traveling by car

Traveling by bus

time
Out of bus
service hours
Activity (a)Activity (b)afternoon

The required time
for the activity
Consultationhours

morning

E

space
E
CB D
A
CB D
A
home
home
Figure 1 Activity participation under space-time constraints

Ａ
Ｄ

Ｅ

Route III

Ｃ

Ａ’

Ｂ

Route I
Route II
0

2

4

Kilometers

Figure 2 Residential zones (mesh areas), transport network and hospitals in the case
study
Table 3 Proportion of the retired elderly who can engage in medical care activity at thehospitals under space-time constraints (%)
TimingA
B
CD
E
At least one*
a.m.
66.5
66.1
54.6
52.4
65.6
67.7
Traveling
p.m.
0.0
79.6
0.0
0.0
78.7
80.6
by cara.m. or p.m.
66.5
95.1
54.6
52.4
94.9
95.4
a.m.
54.5
45.8
37.0
32.2
37.6
55.9
Traveling
p.m.
0.0
65.4
0.0
0.0
55.1
68.0
by busa.m. or p.m.
54.5
82.6
37.0
32.2
72.5
85.3
Weighted
a.m.
56.8
50.1
39.9
36.0
43.7
57.9
by license
p.m.
0.0
67.1
0.0
0.0
58.6
69.3
holdinga.m. or p.m.
56.8
83.9
39.9
36.0
75.1
86.2
* % the elderly who can engage in medical care activity at least one hospital among thefive hospitals
shows an example of the feasibility of activity participation under space-time prism
constraints. Suppose an individual has an activity schedule and lives under the spatialenvironment as shown in Figure 1. In case he travels by car in the morning, he canengage in the activity at Hospital B, C and D, but cannot engage in at Hospital A and E,
because he cannot have enough time at the hospitals under his prism constraint. In theafternoon, he can engage in the activity at Hospital B and E. On the other hand, in casehe travels by bus, he cannot engage in the activity at Hospital E in the afternoon,
because of longer travel time than that by car. Residential zones (mesh areas), road andbus networks, and locations of hospitals are shown in Figure 2.

Table 3 shows the proportion of the retired elderly who can engage in medical care
activity at each hospital under space-time constraints. The result shows the higher
percentage in case all the elderly can travel by car than in case travel by bus. The
indices depend on both travel times and the consultation hours, not necessarily showing
higher values at the hospitals where travel times are shorter. In the afternoon, since theretired elderly were not strongly restricted by prism constraints, the percentages wererelatively high.
Evaluation of accessibility after relocation of the hospital and impacts ofaccessibility-enhancing policies
Hospital A relocated in 1998 from city center to suburban area (A’ in Figure 2), becauseof the worn-out facilities and the shortage of its floor area. The hospital had expected anincrease of outpatients and visitors coming by car and prepared more parking lots. But,
it had concerned about lower level of bus service comparing the original location andapplied to bus companies for bus service improvement. In this section, impacts ofaccessibility-enhancing policies regarding bus services and hospitals are simulated.
Due to relocation of Hospital A, travel time by car became 1.7 times as long as before,
travel time by bus 1.8 times, generalized travel time by bus 2.1 times, respectively. The
proportion of the retired elderly who could engage in medical care activity decreased in
20%. These results show the decrease in accessibility after relocation of Hospital A.
Bus companies in Akita were examining to increase the frequency of the existing route I
and to introduce new routes II and III (as shown in Figure 2). On the other hand,
Hospital A was planning to introduce new management system for reducing patients’
waiting time preceding consultation. If Hospital A did consultation for outpatients also
in the afternoon, many patients were expected to come to the hospital, but the limited
number of medical doctors working at the hospital prevented from doing this. We
analyzed how accessibility would be changed by increasing the frequency (decreasing
headway) of route I and introducing new routes II and III as an improvement intransportation side, and by decreasing the required activity duration at the hospital andTable 4 Alternative scenarios for accessibility-enhancing policies
Headway
Headway of
Activity
The consultation
Alternative scenariosof route I new routes II
durationhours(min.)and III (min.)(min.)Do nothing
60—
120
7:00–11:30
B1
45
—
120
7:00–11:30
B2
30
—
120
7:00–11:30
B3
15
—
120
7:00–11:30
Bus service
B4
45
45
120
7:00–11:30
B5
30
30
120
7:00–11:30
B6
15
15
120
7:00–11:30
Activity
A160—
90
7:00–11:30
duration60
7:00–11:30
A260—
7:00–11:30
S1
60
—
120
Consultationand 12:00–15:00
hours
7:00–11:30
S2
60
—
120
and 12:00–16:00

Table 5 Proportion of the retired elderly who can engage in medical care activity (%)
Hospital A
At least one hospital
Alternative scenarios
a.m. ora.m. ora.m.
p.m.
a.m. p.m.
p.m.
p.m.
Before relocation
Do nothing 56.8
0.0
56.8
57.9 69.3
86.2
of Hospital A
Do nothing 36.3
0.0
36.3
54.0 69.3
86.2
B1
38.8
0.0
38.8
54.2 69.3
86.3
B2
41.9
0.0
41.9
54.8 69.3
86.3
B3
45.2
0.0
45.2
55.2 69.6
86.6
B4
43.0
0.0
43.0
54.5 69.4
86.3
After relocation of
B5
46.6
0.0
42.6
55.1 69.4
86.4
Hospital A
B6
49.2
0.0
49.2
55.5 69.7
86.7
A1
47.2
0.0
47.2
55.7 69.3
86.2
A2
58.2
0.0
58.2
60.1 69.3
86.2
S1
36.3
53.2
68.8
54.0 69.4
86.4
S2
36.3
53.4
68.9
54.0 69.4
86.4
expanding the consultation hours as an improvement in opportunity side. Table 4 shows
alternative scenarios simulated.
By increasing the frequency in route I, travel time to Hospital A decreased. New routes
II and III contributed travel time decreasing more. But, Hospital A was originallylocated in the best area of bus service, so that after relocation it was difficult to improveaccessibility to the present level by only an improvement in transportation side.
Lastly, the change of space-time accessibility is shown in Table 5, including an
improvement in opportunity side. As total time spending for travel and activity
engagement decreased by reduction of activity duration, the proportions of the retired
elderly who could engage in the activity increased. In case Hospital A did consultationfor outpatients also in the afternoon, the proportion increased dramatically. However,the proportion of the elderly who could engage in the activity at least one hospital rarelychanged by any scenarios. Since, before the relocation, the distance to Hospital A waslong and level of bus service was lower for people living in suburban areas, there
remained the retired elderly who could not engage in the activity at the hospitals after
the relocation by introducing the accessibility-enhancing policies.

Conclusions
The evaluation of space-time accessibility considering activity engagement underspace-time constraints was very useful and this could be used as one of the measures ofmobility-related social exclusion. The method made it possible to evaluate the impactsof accessibility-enhancing policies including not only an improvement in transportationside (i.e. increase in frequency of the existent bus route and introduction of new bus
routes), but also an improvement in opportunity side (i.e. extension of consultation
hours and reduction in the required time for the activity). Further research concerns
analyses of pick-up (car passenger) mode availability by introducing car driver’s
schedule constraints (Ohmori et al., 2003b), use of more detailed GIS data for more
micro level analyses (e.g. more detailed zones and pedestrian road conditions) andaccessibility evaluation including activities engaged in by information andcommunications technologies such as telemedicine.

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