Operations of a Shared, Autonomous Electric Vehicle Fleet: Implications of Vehicle Charging Infrastructure Decisions
The nexus of autonomous vehicle (AV) and electric vehicle (EV) technologies has important potential impacts on our transportation systems, particularly in the case of shared use vehicles. There are natural synergies between shared AV fleets and EV technology, since fleets of AVs resolve the practical limitations of today's non autonomous EVs, including traveler range anxiety, access to charging infrastructure, and charging time management. Fleet managed AVs relieve such concerns, managing range and charging activities based on real time trip demand and established charging station locations, as demonstrated in this paper. This work explores the management of a fleet of shared autonomous (battery only) electric vehicles (SAEVs) in a regional discrete time, agent based model. The simulation examines the operation of SAEVs under various vehicle range and charging infrastructure scenarios in a gridded city modeled roughly after the densities of Austin, Texas. Results indicate that fleet size is sensitive to battery recharge time and vehicle range, with each 80 mile range SAEV replacing 3.7 privately owned vehicles and each 200 mile range SAEV replacing 5.5 privately owned vehicles, under Level II (240 volt AC) charging. With Level III 480 volt DC fast charging infrastructure in place, these ratios rise to 5.4 vehicles for the 80 mile range SAEV and 6.8 vehicles for the 200 mile range SAEV. SAEVs can serve 96 to 98% of trip requests with average wait times between 7 and 10 minutes per trip. However, due to the need to travel while "empty" for charging and passenger pick up, SAEV fleets are predicted to generate an additional 7.1 to 14.0% of travel miles. Financial analysis suggests that the combined cost of charging infrastructure, vehicle capital and maintenance, electricity, insurance, and registration for a fleet of SAEVs ranges from $0.42 to $0.49 per occupied mile traveled, which implies SAEV service can be offered at the equivalent per mile cost of private vehicle ownership for low mileage households, and thus be competitive with current manually driven carsharing services and significantly cheaper than on demand driver operated transportation services. The availability of inductive (wireless) charging infrastructure allows SAEVs to be price competitive with non electric SAVs (when gasoline prices are between $2.18 and $3.50 per gallon) However, charging SAEVs at attendant operated stations with traditional corded chargers incurs an additional $0.08 per mile compared to wireless charging, and as such would only be price competitive with SAVs when gasoline reaches $4.35 to $5.70 per gallon.