Shared e-scooters, mode substitution and life-cycle greenhouse gas emissions

Introduction: Shared e-scooters are promoted as a sustainable alternative to the private car, but the evidence on which modes they replace and on their life-cycle greenhouse gas emissions remains contested. Methods: A systematic review following PRISMA 2020. After deduplication, 433 records were screened and 15 studies were included. Results: Self-reported surveys showed that shared e-scooter trips most often replace walking (37.8 to 46.9 percent) and public transport (25.6 to 32.0 percent), with car replacement of 3 to 12.6 percent; inferred and revealed-preference designs reported car substitution up to 34.4 percent. Life-cycle emission factors ranged from 30 to 320 g CO2e per passenger-kilometre, driven mainly by scooter lifetime, electricity mix and fleet operations. Net benefits appeared only where car trips were replaced. Conclusions: Shared e-scooters reduce greenhouse gas emissions only when they replace motorized trips and when fleets achieve long lifetimes in low-carbon grids; in most observed settings they replace active and public transport trips and can increase emissions.