SPACE-TIME ACCESSIBILITY MEASURES FOR EVALUATING MOBILITY-RELATEDSOCIAL EXCLUSION OF THE ELDERLY

Izumiyama, Hiroshi
Institute of Environmental Studies, The University of Tokyo, Tokyo, Japan
Email: izumiyama@ut.t.u-tokyo.ac.jp
Ohmori, Nobuaki
Department of Urban Engineering, The University of Tokyo, Tokyo, Japan
Email: nobuaki@ut.t.u-tokyo.ac.jp
Harata, Noboru
Department of Urban Engineering, The University of Tokyo, Tokyo, Japan
Email: nhara@ut.t.u-tokyo.ac.jp

SUMMARY
Towards aged society, it is important to provide better mobility and accessibility for theelderly and disabled people, so that they can live their independent lives in community.
The elderly have a wide range of constraints on participating in out-of-home activities; forexample, physical disadvantages, keeping regular lifestyles for their health andentrenched habits, limited space-time areas of activity engagement for both safety
problems and limited ability of information acquisition, and monetary budget constraint.
In addition, people who cannot drive a car depend more on public transport service andneed their household members’ help when they go out. Therefore, their choice sets offeasible activity-travel patterns are strongly restricted by these constraints. This isregarded as one of the mobility-related “social exclusion” problems. It should be useful toanalyze the feasibility of activity participation of the elderly under personal andenvironmental constraints they face in their daily lives. The objectives of this study are(1) to propose and validate a method for evaluating mobility-related social exclusion
based on the concept of space-time accessibility and (2) to investigate the elderly
people’s constraints in their activity schedules by examining how they adjust activity
schedules when participating in out-of-home activities.

Space-time accessibility measures represent the ease to participate in out-of-homeactivities, considering possibility of activity engagement under space-time constraints.
Data required for the analysis consist of activity schedules of individuals, transportation
network, and locations and opening hours of activity opportunities. In December 2005,
we conducted a questionnaire survey to collect information on activity diaries andscheduling adjustment for participating in a medical care activity at two general hospitals.
The respondents were people of 65 years and over who came to either of the two
hospitals in Akita city. The number of samples was 70. Based on space-time constraintsof daily in-home mandatory and maintenance activities, space-time accessibility
measures to participating in a medical care activity at the hospitals were calculated.
Information on spatial distribution of the elderly population from the Population Census
data was used for analysis of accessibility evaluation in urban scale. Geographic
information system (GIS) was used for data management and representation of theresults.
From a series of analyses, we identified a considerable gap in accessibility between
individuals with and without car, and between urban and suburban areas. It was also
found that the elderly adjusted their activity schedules (adjustment in start time, durationof activities) to participate in a medical care activity as compared to their daily regularschedules. The proposed method makes it possible to evaluate the impacts of policy
measures for mitigating mobility-related social exclusion, which incorporate not only the
improvement of transportation services, but also the improvement of activity
opportunities and household activity schedules.
Key Words: space-time accessibility; social exclusion; the elderly

INTRODUCTION
Towards aged society, it is important to provide better mobility and accessibility for theelderly and disabled people, so that they can live their independent lives in community.
The elderly have a wide range of constraints on participating in out-of-home activities; forexample, physical disadvantages, keeping regular lifestyle for their health andentrenched habits, limited space-time areas of activity engagement for both safety
problems and limited 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, theirchoice sets of feasible activity-travel patterns are strongly restricted by these constraints.
Furthermore, especially in local cities, motorization has been promoting relocation oflarge-scale facilities (shopping centers, hospitals, etc.) to suburban areas, and the levelof 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 theylike. This is regarded as the mobility-related “social exclusion” problem. Kenyon et al.
(2002) defined the 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 theassumption of high mobility.” It should be useful to analyze the feasibility of activity
participation of the elderly under personal and environmental constraints they face intheir daily lives.
Conventionally, travel time or generalized travel time from a reference location such ashome or the workplace to an activity opportunity is used for a basic measure ofaccessibility. However, it represents only the effort (or ease) of overcoming spatial
separation. Essentially, both spatial and temporal components of accessibility, which
represent potential of participating in activities at opportunities, should be evaluatedtaking into account the fact that travel is a demand derived from engaging in activities.
The space-time prism constraint formalized by Hägerstrand (1970) is a very useful idea
for specifying alternative feasible activity-travel patterns in time and space. Burns (1979)
expanded the concept of accessibility into space-time dimensions, “space-timeaccessibility,” introducing the activity duration at opportunities based on the prism
constraints. Lenntorp (1978) operationalized Hägerstrand’s approach by developing
PESASP model that calculated the total number of space-time paths given a specificactivity program and the urban transport network. In recent studies, Kwan (1998) andMiller (1999) operationalized the space-time accessibility measures on a real worldtransport network using Geographic Information Systems (GIS). These space-timeaccessibility measures represent the potential of activity participation under space-time
constraints, which incorporates activity duration at and opening hours of activity
opportunities, and individual activity schedule. Therefore, it could be useful as a measureof mobility-related social exclusion. The authors have proposed the advanced
space-time prism concept with individual scheduling adjustment (Ohmori et al., 1999)
and evaluated the impacts of changes in transport system and activity opportunities onspace-time accessibility to hospitals for the elderly (Ohmori and Harata, 2004). However,it has not been investigated how the elderly adjust their schedules. The objectives of thisstudy are (1) to propose and validate a method for evaluating mobility-related social
exclusion based on the concept of space-time accessibility and (2) to investigate theelderly people’s constraints in their activity schedules by examining how they adjust
activity schedules when participating in out-of-home activities.

METHODS FOR MEASURING ACCESSIBILITY
1. Study Area
A case study was conducted in Akita, a local city in Japan. The population consists ofabout 318,000 and the ratio of people aged 65 years and over (the elderly) is 17.5% (the2000 Population Census). In the near future, the ratio of the elderly of Akita prefecture is
expected to be the highest in Japan. Accessibility to a medical care activity at general
hospitals was evaluated as one of the most important activities for the elderly people’s
daily lives. Two accessibility measures were defined in this study: (1) the minimum
required time for travel and activity participation; and (2) the percentage of the elderly
who can engage in the activity under space-time prism constraints. Two travel modes,
car and bus (with walk access/egress), were considered in the analyses. Data on
population of the elderly at 216 residential zones (about 1 km × 1 km square), road andbus networks, and location of general hospitals with the attribute of opening(consultation) hours were prepared in MapInfo GIS.
2. Minimum required time for travel and activity participation
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 the equivalent coefficients of different modes:
in-vehicle time, walk access/egress, transfer and waiting (Nitta et al., 1995; Ohmori andHarata, 2004). Bus network data (a total of 800 bus stops and 121 routes) were originallyprepared by the authors. The minimum required time for travel and activity participation
was defined as the total time of traveling from home to the hospital and from the hospital
to home and the required activity time at the hospital.
3. Feasibility of activity participation as a space-time accessibility measureThis measure explicitly incorporates not only the minimum required time for travel andactivity participation but also space-time prism constraints formalized from the individual
activity schedule and opening hours of opportunities. Based on the authors’ previous
work, activities were classified into three types: Activity (a) is an almost fixed activity(sleep and meals); Activity (b) is a planned but flexible activity (personal care, housework,etc.); and Activity (c) is a discretionary activity (hobbies and entertainment, readingbooks, watching TV, etc.). The feasibility of medical care activity participation at hospitals
was calculated based on the advanced space-time prism concept (Ohmori et al., 1999
and 2003); a person starts traveling at the earliest end time of an Activity (a), arrives at
the hospital within the consultation hours, spends time for waiting, consulting a doctor
and getting some medicine, leaves the hospital and returns home at the latest start timeof the next Activity (a) (see Figure 1). In the authors’ previous study, it was assumed thatthe start/end time of activity (a) was fixed, whereas in this study the start/end time ofactivity (a) can be adjusted within a certain time window.
activity (a)Traveling by bus

Traveling by car
activity (b)time

Hospital

The latest start time of
the next activity (a)Consultation
hours
The required
activity time
The earliest end timeof an activity (a)
ABC

D

home

E

ABC

D

E

space

home

Figure 1 Differences in feasibility of activity participation at hospitals when traveling by
car and bus under space-time constraints
4. Questionnaire survey
We conducted a questionnaire survey in December 2005, in Akita city. A total of 357
questionnaire sheets were distributed to the elderly people at two major general
hospitals (Hospital A and B in Figures 2, 3 and 4) and 70 valid questionnaires werereturned. Information obtained was socio-demographic characteristics (age, sex,
occupation, household members, home location, license holding, etc.), activity-travel

diary on the day, the earliest and latest start time and duration of sleeping and having
meals in daily life, and undesired adjustment of activity schedules on the survey day. A
total of 42 respondents were male, 34 were 75 years or over, 38 had driving license andonly 1 was a fulltime employee. Travel mode to the hospitals were car-driver (32respondents), car-passenger (18), bus (7), taxi (6), walk (4) and other (3). Some
respondents used a different travel mode in returning home, e.g., car-passenger whencoming to the hospital but taxi when returning home.

EVALUATION OF ACCESSIBILITY
1. Minimum required time for travel and activity participation
In Figure 2, each square zone represents the “shortest” required time for travel andactivity participation among 5 hospitals. When traveling by car, the required time is100–120 minutes for about half of the zones and even the maximum time is less than
180 minutes. However, when traveling by bus, the required time is less than 150 minutes
for only about 20% of the zones and for about 30% of the zones mainly in north andsouth part of the city is more than 200 minutes. Figure 3 shows its difference between
car and bus. For about 50% of the zones, the difference is more than 50 minutes. In
particular, the elderly living in suburban areas and without car availability need longer
time for consulting a doctor at general hospitals.
2. Feasibility of activity participation as a space-time accessibility measure
It was assumed that daily activity schedules of the elderly depended on age and sex. For
4 segment groups, younger (aged 65–74 years) men, younger women, older (75 years
and over) men and older women, different sets of activity schedules were created from a
total of 65 respondents’ information on the timing and duration of Activities (a) and (b) as
described in the previous section. The elderly of 4 groups in each 216 zone were
supposed to have the same distribution of activity schedules as the sample. The
percentage of the elderly who can engage in the activity at hospitals was calculatedusing the number of population of the 4 groups in the 2000 Population Census data. The
required activity time at the hospital was set as 1.68 hours (the mean time spent at
hospitals in the activity diary). As shown in Figure 4, when traveling by car, thepercentages of the elderly who cannot engage in the activity at any of the five hospitals
are less than 5% for most zones and the maximum is less than 10%. However, whentraveling by bus, the number of the zones of where the percentage is less than 10% isTotal numberof zones

Traveling by car

Total numberof zones

Traveling by bus

Figure 2 Minimum required time for engaging in a medical activity when traveling by car
and bus in each zone (minutes)

Total numberof zones

Figure 3 Difference of the minimum required time between traveling by car and bus ineach zone (minutes)

only 95 and there are the zones showing relatively higher percentages (more than 30%)
mainly in north and south part of the city. The result shows the existence of the elderly
who cannot engage in consulting a doctor at any general hospitals when keeping their
daily regular activity schedules.

Total numberof zones

Traveling by car

Total numberof zones

Traveling by bus

Figure 4 Percentages of the elderly who cannot participate in a medical care activity at
any of the five hospitals under space-time constraints in each zone
4. Activity adjustment when going to hospital
Respondents were asked whether they had any of the following activities on the survey
day:- Activities of which they would like to have increased or decreased the duration morethan 15 minutes;- Activities which they would like to have started more than 15 minutes earlier or later;- Activities which they would like to have conducted before (or after) noon; and- Activities which they would like to have conducted but were not able to have done at all.
it is considered that the respondents who had any of the above activities made someundesired adjustment of their activity schedules for participating in a medical activity at
hospitals. A total of 33 respondents had the activities and among them 19 respondents
adjusted Activity (a); for example, 8 of them delayed the start time of having lunch, 5advanced the start time of having breakfast, 3 reduced the duration of sleeping, etc. The

ratio of the respondents who did this undesired adjustment of Activity (a) was higher for
female (39% of the female respondents), younger elderly (39%), car-passenger user
(39%) and bus user (43%). If the elderly came to hospitals by car-passenger mode
escorted by other household members, we asked the drivers whether they did undesired
activity adjustment for the escorting the elderly. We received answers from only 8 drivers
but 3 of them answered that they did it for mandatory and maintenance activities.
Medical care activity participation at hospitals affected not only activity schedule of theelderly but also that of the drivers. The result also supports that the proposed space-timeaccessibility measure which evaluates possibility of out-of-home activity participation
within space-time prisms with scheduling adjustment is reasonably operationalized.

CONCLUSION
From a series of analyses, we identified a considerable gap in accessibility between
individuals with and without car, and between urban and suburban areas. It was also
found that the elderly did undesired adjustment of their activity schedules (adjustment instart time, duration of activities) to participate in medical care activity at hospitals
compared to those in regular days, which also supports the validity of the space-timeaccessibility measure with scheduling adjustment previously proposed by the authors(Ohmori et al., 1999 and 2003; Ohmori and Harata, 2004). The method makes it possible
to evaluate the impacts of policy measures for mitigating mobility-related social exclusion,
which incorporate not only the improvement of transportation services, but also theimprovement of activity opportunities and household activity schedules. Further researchconcerns analyses of car-passenger mode availability by introducing car-driver’s
schedule constraints (Ohmori et al., 2003), the use of more detailed GIS data on zones
and transport network for taking account of walk environment, and accessibility
evaluation including activities engaged in by information and communications
technologies (ICTs) such as telemedicine. This study examined accessibility as thepotential of social exclusion, whereas investigating the relationship between accessibilityand “activity space” (Schönfelder and Axhausen, 2003) based on the revealed travel
pattern needs to be explored in the future research.
REFERENCES
Burns, L., 1979. Transportation, temporal, and spatial components of accessibility.

LexingtonBooks, Lexington.
Hägerstrand, T., 1970. What about people in regional science?, Papers of the Regional
Science Association, 24, pp.7-21.
Kenyon, S., Lyons, G. and Rafferty, J., 2002. Transport and social exclusion:
investigating the possibility of promoting inclusion through virtual mobility, Journal ofTransport Geography, 10, pp.207-219.
Kwan, M.-P., 1998. Space-time and integral measures of individual accessibility: A
comparative analysis using a point-based framework, Geographical Analysis, 30(3),pp.191-216.
Kwan, M.-P., 1999. Gender and individual access to urban opportunities; a study using
space-time measures, Professional Geographer, 5(2), pp.210-227.
Lenntorp, B., 1978. A time-geographic simulation model of individual activity
programmes. In T. Carlstein, D. Parks and N. Thrift, eds., Timing Space and Spacing
Time 2, Human Activity and Time Geography. Arnold, London.
Miller, H., 1999. Measuring space-time accessibility benefits within transportation
networks: Basic theory and computational procedures, Geographical Analysis, 31(2),pp.187-212.
National Institute of Population and Social Security Research, http://www.ipss.go.jp/
Nitta, Y. Mihoshi, A. and Mori, Y., 1995. Basic study on special bus service planning for
improving mobility of elderly, Journal of Infrastructure and Management, No.518/IV-28,
pp.43-54. (in Japanese)
Ohmori, N. and Harata, N., 2004. Evaluation of space-time accessibility considering daily
activity engagement of the elderly, Proceedings of TRANSED2004, CD-ROM.
Ohmori, N., Muromachi, Y., Harata, N. and Ohta, K., 1999. A study on accessibility andgoing-out behavior of aged people considering daily activity pattern, Journal of theEastern Asia Society for Transportation Studies, 3(5), pp.139-153.
Ohmori, N., Muromachi, Y., Harata, N. and Ohta, K., 2003. Simulation model for activity
planning (SMAP): GIS-based gaming simulation. In C.-H. Park, et al. eds., Selected
Proceedings from the 9th World Conference on Transport Research, Pergamon.
Schönfelder, S. and Axhausen, K., 2003. Activity space: measures of social exclusion?,Transport Policy, 10(4), pp.273-286.
The Population Census. http://www.stat.go.jp/data/kokusei/