Exploring the Non-linear Relationship between E-scooter Ridership and the Built Environment

Shared e-scooter has become a popular mode of transportation in the United States. Despite the increasing attention paid to the e-scooter patterns and the influencing factors of e-scooter trips, few studies have explored the relative importance of the built environment and its threshold effect on e-scooters. Using the trip records of all the shared e-scooters in Austin, Texas, USA from August 2018 to March 2021, the origins and destinations of which are recorded by census tract, this study employs gradient boosting decision trees (GBDT) to examine the non-linear effects of the built environment on the e-scooter ridership. The results show that the relative importance of all built environment factors, with a contribution of 70.45%, is higher than that of socio-demographics (29.54%), and the distance from census tract to city center and bike lane density are the two most essential attributes to e-scooter ridership. Besides, all built environment factors have salient non-linear and threshold effects on the e-scooter ridership. For example, distance to the city center has a significant negative impact on e-scooter trips with an effective range of 6.5 kilometers, and the bike lane density is positively associated with the e-scooter ridership in a certain range. By quantifying each built environment factor's relative importance and threshold effect on e-scooters, this paper can provide e-scooter operators with fleet deployment and operation management suggestions and guide planning departments to build an e-scooter-friendly environment.