## 4 Evaluating the Effect of the Maze Meltdown
### Effect on BART
The black bars in the figure indicate the frequency of stations at which the observed \(p\)-values were less than 0.05 indicating a significant increase in ridership. The locations of the BART stations at which pronounced increases in daily ridership were observed are shown in Figure 3b (see stations represented by black circles). The dark and light grey  
Figure 2: (**a**) Map of Bay Area Rapid Transit (BART) stations; (**b**) comparison of the average weekday hourly ridership between N1 and R1 at El Cerrito Plaza station; (**c**) comparison of the average weekday hourly ridership between N1 and R2 at El Cerrito Plaza station; (**d**) comparison of the average weekday hourly ridership between N1 and N2 at El Cerrito Plaza station; and (**e**) empirical probability distribution of the daily demand observed at El Cerrito Plaza station prior to the Maze Meltdown. bars in the figure show the number of stations where the observed \(p\)-values were 0.05-0.1 and 0.1-0.2, respectively (see stations represented by dark and light grey circles in Figure 3b). The white bars in the figure indicate the frequency of stations where observed \(p\)-values exceeded 0.2. Figure 3 shows the corresponding statistics from the R2 and N2 period. Figure 3: (**a**) Histogram of p-values of the average weekday daily BART entrance ridership during R1; (**b**) map of values shown in Figure 3a; (**c**) histogram of \(p\)-values of the average weekday daily BART entrance ridership during R2; (**d**) map of values shown in Figure 3c; (**e**) histogram of \(p\)-values of the average weekday daily BART entrance ridership during N2; and (**f**) map of values shown in Figure 3e. Significant increases in BART ridership were observed at most stations located in the Richmond, Walnut Creek, and Concord areas, whereas the stations located south of the Oakland, Hayward, and Fremont areas remained relatively unaffected during R1: the impact of the closure was not uniform among the stations. The stations marked with black circles (see Figure 3b,d,e) reported more pronounced increases in demand than other stations (i.e., \(p\)-values less than 0.05). The increased in BART ridership quickly diminished during R2, after the reopening of the I-80W to I-880S connector (see arrow 2 in Figure 1b). The number of patrons entering stations returned to the normal state, which is indicated by \(p\)-values higher than 0.05 (see Figure 3c) and darker colored circles turning to a lighter color (see Figure 3d). Notice BART stations located in remote locations in the Richmond, Concord, and Walnut Creek areas retained high numbers of patrons (see stations in Figure 3f) even after all the connectors are restored. Additionally, two stations in Oakland, which are primary central business districts, reported high numbers of patrons using those stations (see station 19 and 20 in Figure 3f). Monitoring the changes in ridership using \(p\)-values can be instrumental in evaluating how statistically significant the change is. However, it can also be misleading when the average ridership during N1 is small. Notice how station 42 displayed a low \(p\)-value during R1 (see Figure 3b), a high \(p\)-value during R2 (see Figure 3d), and low \(p\)-value during N2 (see Figure 3f). This is due to the fact that average daily ridership at station 42 was only 2200 during N1, as a result, even a moderate increase of several hundred passengers could significantly alter the \(p\)-value. Excluding station 42, ridership at some of the remote stations remained significantly high during N2 compared with ridership during N1. This may due, in part, to the fact that many of the passengers using those BART stations did not travel via BART prior to the incident. Having been forced to use BART during the freeway repairs, they may have discovered its benefits and convenience, and continued to travel via BART even after traffic conditions returned to the normal state.