## 5 Disaggregate Analysis
The significance of the mode dummy variable indicated that the commuting time of the target mode was significantly different from the travel time of the driving trips. In the pooled model, the dummy variables for bus, passenger, rail, and walk were significant, and their coefficients were positive, which means that the travel times of these modes were significantly longer than the driving time after controlling for other attributes. The long travel times of these modes coupled with their increased mode share contributed to the increased overall commuting time. As expected, the coefficients of the interaction terms between mode and travel distance were all significant. The coefficients for these interaction terms were inversely related to the speed of a mode. For example, in the first column of Table 7, the coefficient for the driving-distance interaction term is 1.52, which means that it took 1.52 min to travel one mile by driving at an average speed of 39.5 miles/hour. In the segmented models, all coefficients for the interaction terms, except that between rail and travel distance, were larger in 1994 than in 2011. This indicates that the speed of all modes increased from 1994 to 2011 for both CBD and non-CBD trips, except for the rail mode. The interaction term between driving and peak was significant in all models, while that between peak and other modes was not significant. This is because driving is more susceptible to congestion than the other modes. In the two CBD models, the coefficient for the interaction term between driving and peak was smaller in the 2011 model than in the 1994 model. This indicates that the peak congestion effect on driving was less severe in 2011 than in 1994. A possible explanation is that there were fewer commuting drivers, as some of them shifted to non-driving modes, as shown in the mode share section above. Interestingly, the peak effect was more severe in 2011 for the non-CBD trips, as the coefficient for the interaction term between driving and peak was larger in the 2011 non-CBD model than in the 1994 non-CBD model. Among the socio-demographic variables, older age had a significant effect on the commuting time in the pooled model. Most dummy variables for car ownership were not significant, with the \"no vehicle\" category as the reference category. Gender was not associated with commuting time, which means that there was no difference in commuting time between males and females. The household size was found not to be associated with \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Variable** & **Pooled** & **1994 CBD** & **1994 Non-CBD** & **2011 CBD** & **2011 Non-CBD** \\ \hline ModeRail:TripDist & 1.730 *** & 0.959 ** & 1.600 ** & 1.500 *** & 1.800 *** \\  & (0.074) & (0.446) & (0.711) & (0.137) & (0.096) \\ ModeWalk:TripDist & 20.800 *** & 31.000 *** & 32.200 *** & 20,900 *** & 18.500 *** \\  & (0.967) & (5.320) & (2.560) & (2.940) & (1.250) \\ ModeDriving:Peak & 3.020 *** & 5.770 *** & 2.440 *** & 2.420 * & 2.960 *** \\  & (0.223) & (1.620) & (0.332) & (1.300) & (0.300) \\ ModeBike:Peak & 1.930 * & 0.382 & 1.040 & 0.709 & 2.550 ** \\  & (0.991) & (11.000) & (2.880) & (2.960) & (1.140) \\ ModeBus:Peak & 2.070 ** & 3.900 & 3.910 & 1.300 & 0.721 \\  & (0.976) & (2.650) & (2.480) & (1.920) & (1.560) \\ ModePassenger:Peak & 0.609 & \(-\)4.360 & 1.240 & \(-\)5.710 & 1.240 \\  & (0.933) & (4.670) & (1.910) & (7.380) & (1.100) \\ ModeRail:Peak & 0.482 & 14.600 * & \(-\)2.020 & \(-\)0.282 & \(-\)1.640 \\  & (1.450) & (7.480) & (6.470) & (2.370) & (2.020) \\ ModeWalk:Peak & 0.565 & 2.000 & 0.003 & 0.179 & \(-\)0.276 \\  & (0.824) & (3.730) & (1.671) & (4.110) & (1.040) \\  & 12.600 *** & 11.700 * & 6.610 ** & 15.800 ** & 10.500 *** \\ Constant & (1.170) & (6.540) & (2.870) & (7.920) & (1.350) \\ Observations & 10,366 & 500 & 2976 & 1068 & 5.822 \\ Adjusted R2 & 0.670 & 0.607 & 0.678 & 0.610 & 0.691 \\ \hline \end{tabular} Note: * \(p<0.1\); ** \(p<0.05\); *** \(p<0.01\). Std error in parentheses.  
\end{table} 
Table 7: _Cont._the commuting time.