Are shared automated vehicles good for public- or private-transport-oriented cities (or neither)?

• We analytically derive the VKT change due to introduction of SAVs with ridesharing. • Our derivation combines mode choice and operational aspects in a minimalistic city. • Cities with strong public transport ridership are at risk of large VKT increase. • Cities with mostly private transport use would maintain their VKT levels. • SAVs should have medium capacities and good on-board experience to reduce VKT. Simulation studies suggest that Shared Automated Vehicles (SAVs) could reduce the total vehicle kilometres travelled (VKT) thanks to efficiently pooling multiple users in one vehicle. However, mode choice studies indicate that SAVs would attract mostly public transport users, leading to an increase in VKT. This paper is among the first to combine these operational and behavioural expectations and the first to do so analytically. In our theoretical set-up, travellers choose between car, public transport, and SAVs, depending on their individual valuation of private travel and other attributes of each mode. We find that the introduction of SAVs lead to a VKT change in public-transport-oriented cities ranging from a small decrease to a large increase, where the latter is true for plausible parameter settings and hence is a cautionary point for SAV-introduction policies. Conversely, SAVs would attract only few travellers in private-transport-oriented cities and therefore would not significantly impact VKT.