Conclusion

This study has conducted the explorations on two latent constructs of travelers’

considerations. The first topic aims to explore the vehicle dependence of motorcyclists, and the second topic is to measure the physical ability perceived by the elderly bus passengers.

In the first part of this study, we have explored vehicle dependence, taking account of subjective considerations of individual travelers. Vehicle dependence, arising from economic considerations, psychological preference, and habitual behavior, is formulated here as a subjective latent construct that acts in a person’s mode choice. The Rasch model is reviewed, and suggested as an instrument to measure such a latent construct. An empirical analysis of motorcycle dependence was performed using self-rated information about eight items from 321 motorcyclists in Taipei. The detailed measures with respect to the items and persons have been reported, and the validity of Rasch measurement has been verified by reliability indices and fit statistics. We have also interpreted the results from assessing the degree of the generalized motorcycle dependence on each kind of trip purpose respectively. By relating the measures of the individual motorcyclist’s dependence with his/her personal socioeconomic characteristics, the findings from these potential relationships have been pointed out.

The empirical results showed that motorcyclists in Taipei tend to depend on their motorcycles to achieve unaccompanied, short-distance, multistop trips; motorcyclists under the age of 25 who were inferior in economic terms and did not use an automobile showed relatively higher measures of motorcycle dependence. Some interesting results showed that

the dual-mode users have significantly lower dependence on motorcycles than have those motorcyclists who do not drive automobiles. This is consistent with the findings of previous studies (Chang, 2002) that automobile driving and motorcycle riding are partially competitive for residents of Taipei. In addition, the dual-mode users who owned their personal automobile parking spaces were found to have less motorcycle dependence than those who did not own automobile parking spaces. This finding can be used to explain the relationship between automobile parking space ownership and motorcycle dependence for dual-mode users.

In summary, we have conceptualized the vehicle dependence in terms of both its socioeconomic and its psychological nature. The measures of vehicle dependence can be further applied into the extending studies on mode choices or travel behavior. For the interval scale property, such a measure can be directly served as explanatory or dependent variable in statistical inference. We believe our effort on exploring the vehicle dependence would benefit researchers in modifying their formulations of mode choice, and policy makers in enacting more effective policies.

The second topic is an explorative trial to realize how the senior bus passengers perceive their own physical abilities when using buses. Such a self-assessment of elderly passengers on their own physical abilities plays a critical role on their willingness of bus patronage. We have developed an approach to measure elderly passengers’ abilities and to explore their difficulties in accomplishing the actions and motions required to patronize the bus service. A conceptual framework about the required actions and motions in bus taking was established and a questionnaire with 18 items was designed to test their ability to use buses. A face-to-face survey was conducted to collect the self-rated information from 304 elderly bus passengers in Taipei. The Rasch model was applied to estimate the difficulty of each item and the ability of each person to use a bus. Detailed measures with respect to the items and persons had been

reported and the validity of Rasch measurement had been verified by the reliability indices and fit statistics. We have interpreted and discussed the findings from the measures of item difficulty, and also have presented the measures on each person and item on a single diagram to see what proportion of the elderly passengers would consider it as difficult in achieving each of the necessary actions or motions in taking the buses.

Results showed the relatively difficult items are mostly about keeping balance on the moving bus and reading the information or discerning the approaching buses at the stations, and the considered levels of physical ability showed negative associated with respondents’

age. Suggestions are made based on improving the facilities or service to help the elderly passengers achieve the necessary actions or motions, which can be summarized as follows:

1. The instant warnings about the bus operations or moving situations might be helpful to warn elderly passengers to take the necessary actions.

2. Providing more priority seats for elderly passengers could avoid the risk of standing on the moving buses.

3. Providing seatbelts for all priority seats would offer further protection for elderly passengers to keep them balanced on the seats.

4. Aids, such as armrest or guardrail, made of flexible materials, are suggested in order to reduce the impact of bumping.

5. The inner-bus monitoring and broadcasting system is also suggested to be equipped near the seat of driver. Once the bus driver detects some tottering elderly people standing on the moving bus, s/he can immediately announce the seat-yielding request via such a broadcasting system.

6. Enlarging the size of characters for the necessary information on the station or bus.

7. Setting the press-to-start vocal instruction buttons on the station and establishing the bus approaching light or voice warning can help the elderly overcome the obstacles due to their visual disabilities.

8. The short-range wireless communication system between bus-stations and bus-drivers might also help the elderly to discern the coming bus. It is suggested to emplace the specific “boarding request” buttons on the bus stations for each bus service route. When the button is pressed, such a boarding request would be transmitted wirelessly and be received by the on-board equipment of the corresponding buses.

9. Integrating the portable personal GPS guidance aids of senior people with the bus GPS system can better ensure the safety and security of the elderly travelers.

To the conclusion, this study has conducted a demonstration on introducing a new approach to measure perceived physical abilities and difficulties of elderly bus passengers in their bus patronage, and on showing its capability to provide the interval scaled measures for further investigation or comparison purposes. The Rasch measurement, which can convert raw ordinal responses into values on an interval scale, was reviewed and employed as the instrument for assessing the relative level of ability of each person and difficulty of each item.

With relating the measures of person ability and item difficulty, the item-person map provides a straightforward and graphical illustration on the corresponding proportion of elderly bus passengers that can achieve in each given item with ease. By extending the measures with indicative variable such as age, some worthy information is clearly disclosed, which provide valuable information to enhance the hardware and software of existing bus systems.