## 3 Route Choice Modeling  
### Data  
GZM network is the urban rail transit system providing traffic service in Guangzhou and the Pearl River Delta area. By the end of 2018, GZM has 14 lines and 257 stations (including 31 transfer stations)in operation, and its operating mileage (478 km) ranks the third all around the world. The daily average ridership of the entire metro network of GZM is over 8 million, and during holidays or some large special events, the daily ridership can surpass 10 million.  
Once the emergency occurs in the GZM network, the operators will estimate the delay time caused by the emergency based on their experiences and the delay information will be send out by official notice, broadcast and passenger information display system (PIDS), as shown in Figure 1. When the emergency-caused delay is less than 10 min, the information will be informed to the passengers on the line where the emergency occurs, when delay time is longer than 10 min and less than 30 min, passengers on adjacent lines will receive the delay information, once the delay time is over 30 min, all metro passengers on the GZM network will get the delay information. Moreover, when the normal operation is resumed, the information will be sent out by all measures so that all metro passengers could get relevant travel information and adjust their travel in time.  
The analysis of metro passengers' route choice behaviors under emergency-caused delays is based on the stated preference (SP) survey carried out in the GZM network. There are totally 6 scenarios in the questionnaire with different origins and destinations alongside with various combinations of route alternatives among multiple traffic modes like metro, bus, and taxi. The attributes of the routes are listed in the questionnaire and each respondent is asked to make their choices in 2 to 4 scenarios based on their travel experiences in the public transportation system, as show in Table 1. After classification and collation of the collected questionnaires, 5520 are valid from 5553 questionnaires (10,128 valid samples can be used for further analysis).  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Route** & **Traffic Mode** & **Route Property** & **Delay Time** \\ \hline \multirow{2}{*}{1} & \multirow{2}{*}{Metro} & The time shortest route before the metro & \multirow{2}{*}{3 to 20 min} \\  & & emergency occurs. & \\ \hline
2 & & & 0 \\ \hline
3 & Metro, metro \& \multirow{2}{*}{
\begin{tabular}{c} Detour routes in metro alone or combined \\ with ground traffic modes like bus or taxi, \\ travel time is longer than route 1. \\ \end{tabular} } & 0 \\ \hline
4 & & & 0 \\ \hline
5 & Bus &
\begin{tabular}{c} Passengers abandon the metro because of \\ the emergency-caused delays and switch to \\ ground traffic modes like buses or taxis. \\ Travel time or travel cost may be higher \\ than the metro routes. \\ \end{tabular} & 0 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Route properties in the survey.  
Figure 1: Delay information sent out by PIDS in the GZM network.  
Among the respondents who participated our survey, male accounts for 62.73% and female accounts for 37.27%, and most of them (94.38%) are younger than 45 years old, which is in line with the majority of metro passengers. Less than 3 transfer times in the metro network can be accepted by a larger proportion of metro passengers, and only about 10% of the passengers can bear 4 or more transfer times. About two-thirds of the metro travelers are commuting to work or school, and the proportion is in line with passengers whose weekly travel times over 6 times or more in the metro system. When a metro delay is inevitable, about 52% of the passengers can only endure waiting for less than 10 min. Other detailed attributes of the respondents of the SP survey is shown in Figure 2.