## 4 Discussion  
The overall statistical analysis as well as the individual correlations performed did not show a significant relationship between any of the operating variables and the average of users recovered in urban bus lines, highlighting the intrinsic complexity not only of the UPT system but also of its physical, economical, and social context. Apart from the poor statistical correlations obtained, which could even be biased by extreme values due to the small sample size, the most remarkable result would be the better recovery of users in suburban lines, an aspect which has already been observed in other studies [39]. Thus, compared to an average recovery of users of 78% in the city of Almeria bus service as a whole, the suburban lines have recovered 87% of the pre-pandemic occupancy level, the same average as the six lines serving the university (Table 2). Although, at a first sight, it could be thought that the lines to the university are the ones driving the average upwards, the results of other suburban lines such as L15 are also surprising, since, despite being the longest and that with the worst frequency (90 min), it ranks second in recovering users compared to 2019 (97%); and L31, the fourth line in length and the second with the worst  
Figure 8: Correlation between the average of users recovered (2022 compared to 2019) and the quantitative variables. frequency (70 min), has recovered 83% of users. Instead, despite the best frequency of the lines serving the main city (32 min on average compared to 42 min for the suburban lines), these are the ones whose behavior is worst in the post-pandemic situation, considered as a whole (Figure 8). This seems to indicate that, regardless of whether they are urban or suburban lines, and independently of the quality of the service, the most determinant factor to choose UPT could be the more or less captive nature of the users, both in the case of students, who are understood to choose UPT for economic reasons [57], and those citizens living in areas no transportation alternatives other than private cars, such as those needing to travel between the smaller centers of the municipality where bike-lanes and pedestrian sidewalks are usually not available [58]. Instead, considering that the dimensions of the main city are approximately 5 km both from north to south and from east to west, the lack of recovery might be due to the shift of users to trips on foot or by bicycle/electric scooter, and it is difficult to attract this percentage of the population back to UPT [59; 60]. Although no specific measurements were taken about the modal shift in the city of Almeria, it is necessary to consider that the average routes within the city would not exceed 30 min on foot [61] and 15 min by bicycle [62]; these values are very competitive taking into account the average frequency of the bus. In this context, it is not surprising that the line with the smallest geographical scope, L1 that serves the historic center, is the one with the worst recovery average. Thus, the captive passengers were more resilient both during the worst phase of the pandemic, when despite perceiving a higher level of risk, they were unable to change their behavior [36], and in the current recovery phase, due to the lack of alternatives [63]. This pattern is likely to be similar in other medium-sized cities, especially in those with housing densities ranging from medium to high, as is the case of many Mediterranean ones. Although these results must be interpreted with caution since only a specific UPT system was analyzed, they seem to indicate that the annual evolution of the number of UPT users should not be approached from a unitary perspective, but considering the existence or not of mobility alternatives for the most popular destinations in the different areas.