How historical and future weather affect bus ridership: a case study in the humid subtropical climate zone

While previous studies have provided insights into the relationship between weather and ridership, how historical and future weather conditions affect bus travel behavior remains to be addressed. And the differences among advancing, current, and lagging effects, between different traveler profiles are not clear. This research aims to fill the gaps by exploring the effects of historical, current, and future weather on bus ridership at hourly scales in Dingjiazhuang, Nanjing, with a typical humid subtropical climate. More than 4 million smart card records, 4 million Global Positioning System (GPS) records, and weather measurements were used over a three-month period. Seasonal autoregressive integrated moving average (SARIMAX) time-series techniques were applied to assess the advancing, current, and lagging effects that five weather conditions, including air temperature, heat index, relative humidity, horizontal visibility, and precipitation, exert on bus ridership at two spatial scales: overall level and origin-destination (OD) pairs. The results showed significant advancing, current, and lagging negative effects of relative humidity on both weekdays and weekends. While current precipitation was negatively associated with bus ridership, the lagging effect was positive. Only significant advancing and current effects of horizontal visibility were captured. Hourly elderly travelers were more affected than younger travelers. In particular, we found that the elderly were more affected by future weather conditions, especially on weekdays. Results yield implications for policymakers to incorporate weather variation information in transit demand monition, which can support requirements for future transport models and develop decision support tools.