4.2.2. Parameter Estimation and Result Analysis
(1) Determining the Number of Latent Classes
This study uses the Mplus software to estimate the model parameters. The number of potential categories increases one by one. The best model, and the parameter estimation results, were obtained by comparing the results of a goodness-of-fit test. The fitness indexes of different LCM categories are shown in
Table 8. The results showed that neither the
χ2 test nor the G2 test rejected the hypothesis (
p > 0.05), suggesting that a potential category model could be established. As the number of categories increases, the BIC index increases. The AIC index decreases first and then increases when the number of categories is five. As the sample size of this study is relatively small (N = 212), the AIC index is taken as the main standard, with four categories in the final selection model.
(2) Parameter Estimation and Reliability Test
The travelers in the sample were divided into four latent classes through a goodness-of-fit test, and the maximum likelihood method was adopted for parameter estimation. The results are shown in
Table 9.
In order to illustrate the credibility of the classification results of the model, the attribution probability matrix for the determined categories is calculated, and the results are shown in
Table 10. It can be seen that the travelers of each category have a high probability of belonging to each potential category—respectively, 0.934, 0.946, 0.886, and 0.976, and the misjudgment rate among all the categories is very low, indicating that the classification effect is good.
(3) Potential Category Naming and Policy Suggestions
Through a cross analysis of explicit variables and categories, the characteristics of various travelers are summarized. The analysis results are shown in
Figure 11,
Figure 12,
Figure 13,
Figure 14,
Figure 15,
Figure 16 and
Figure 17. The OX axes of these figures represent four latent classes of respondents. The OY axes of these figures are the proportion of respondents in each class for different observed variables. The legends of
Figure 11 and
Figure 12 are the observed variables of sex and monthly income. The legends of
Figure 13,
Figure 14 and
Figure 15 are respondents’ answers to ATT4, SN2, and PBC2. The options in the scale are “strongly disagree”, “disagree”, “general”, “agree”, and “strongly agree”, with values ranging from 1 to 5. The legends of
Figure 16 and
Figure 17 are respondents’ sensitivity to the changes in time-cost and expense-cost respectively, that is, high sensitivity to a change in cost, neutral sensitivity to a change in cost, and low sensitivity to a change in cost.
It can be seen from
Figure 11 that, in the CL3 category, the proportion of female travelers is relatively high, while in the other three categories, the proportion of male travelers and female travelers is similar, which is close to the gender distribution of the survey samples.
According to
Figure 12, low-income travelers account for a higher proportion in the CL3 category, while high-income travelers account for a higher proportion in the CL1, CL2, and CL4 categories.
As can be seen from
Figure 13, the CL2 category has the lowest positive evaluation on public transport punctuality; 51.8% of travelers strongly disagree that choosing public transport is more punctual. The CL3 category has the highest positive evaluation of public transport punctuality, as the proportion of travelers who strongly agree that choosing public transport is more punctual reaches 62.2%. The CL1 and CL4 categories are similar; their evaluations of public transport punctuality are neutral and positive.
As can be seen from
Figure 14, the influence of media and public opinion on CL3 travelers is polarized. Here, 44.7% of CL3 categories have a score of 5, while 26.7% have a score of 1. The rest are neutral. Among the CL2 travelers, 25% of the travelers scored 5, 27.1% of the travelers scored 1, and 30.9% of the travelers scored 2. The overall evaluation was low, suggesting that the CL2 category was not easily affected by media and social public opinion. CL1 mainly focuses on scoring 2, 3, and 4, which are evenly distributed. Similar to CL1, CL4 mainly focuses on scoring 3 and 4, which are mostly neutral.
Figure 15 shows that CL2 travelers have the lowest evaluation of public transport waiting time, while CL3 travelers have the highest positive evaluation of public transport waiting time. CL1 and CL4 travelers’ evaluations of the public transport waiting time are mostly neutral and positive.
From
Figure 16, it can be seen that CL1 travelers have the highest sensitivity to changes in time-cost—that is, the change in time-cost that can facilitate a mode transfer is smallest for this type of traveler. CL3 travelers have high sensitivity, while CL2 and CL4 travelers have low–neutral sensitivity.
As can be seen from
Figure 17, CL1 travelers have the highest sensitivity to changes in expense-cost—that is, the change in expense-cost that can facilitate mode transfer is lowest for this type of traveler. CL3 travelers have high sensitivity, CL4 travelers have low–neutral sensitivity, and CL2 travelers have the lowest sensitivity.
To sum up, the naming and policy suggestions for different types of travelers are as follows:
CL1: Rational decision making. This kind of travelers’ evaluations of public transportation punctuality and waiting time are neutral and positive. The travelers have no extreme feelings about the media and public opinion. However, their sensitivities to changes in time-cost and expense-cost are the highest. This type of traveler should be the main target for priority development strategies for public transport and economic leveraging. Reducing the travel time-cost of public transportation (for example, improving the service frequency of public transportation or setting up bus lanes) or increasing the expense-cost of private transportation (for example, raising parking fees in downtown areas or imposing congestion pricing) can attract such travelers to use public transportation.
CL2: Focus on feeling. These kinds of travelers have high incomes, low evaluations of public transportation punctuality and waiting time, and are not easily influenced by media and public opinion. They are also not sensitive to changes in the time-cost and expense-cost. It is speculated that such travelers prefer private transportation. Therefore, this group of people is the main target of restrictive development strategies and travel prohibition strategies. Such travelers who use private transportation will be transferred to public transportation through measures such as traffic restrictions.
CL3: Sensitive to cost. Female travelers in this category account for a relatively high proportion, and their income levels are lower than those in other categories. They are sensitive to changes in time-cost and expense-cost and have the highest positive evaluation of the punctuality and waiting time of public transportation. The influence of media and public opinion on these travelers is polarized. CL3 travelers have the highest positive evaluation of public transport and are very sensitive to changes in cost. Therefore, travelers of this type who often use public transport can be stabilized by priority development strategies for public transport, such as establishing bus lanes or increasing the preferential treatment for public transport. In addition, private traffic users among such travelers could be encouraged to transfer to public transportation by increasing parking fees in central areas or increasing enforcement of parking violations.
CL4: Bounded rational decision making. The income level of such travelers is above average. These travelers are not sensitive to changes in time-cost and expense-cost. Their evaluation of the punctuality and waiting time of public transportation is neutral. The influence of media and public opinion on them is not obvious. It is speculated that the mode choice behavior of such travelers is relatively random. Therefore, these types of travelers could be encouraged to use public transit by restraining private traffic and prioritizing the development of public transport, such as improving the convenience and comfort of public transport, strengthening the publicity of public transport to encourage bus travel, and implementing car restrictions.