  Car sharing is one of the key elements of a Mobility-on-Demand system, but it
still suffers from several shortcomings, the most significant of which is the
fleet unbalance during the day. What is typically observed in car sharing
systems, in fact, is a vehicle shortage in so-called hot spots (i.e., areas
with high demand) and vehicle accumulation in cold spots, due to the patterns
in people flows during the day. In this work, we overview the main approaches
to vehicle redistribution based on the type of vehicles the car sharing fleet
is composed of, and we evaluate their performance using a realistic car sharing
demand derived for a suburban area around Lyon, France. The main result of this
paper is that stackable vehicles can achieve a relocation performance close to
that of autonomous vehicles, significantly improving over the no-relocation
approach and over traditional relocation with standard cars.
