It is a well-known fact that the average number of people carried or in a car is 1.5. Rounded up to a whole number: 2 people per vehicle. Considering that the average number of seats in the car is just under 5, dividing this number by the number of people carried, i.e. 1.5 people, results in only 20% efficiency of rational use of space, and this does not take into account the luggage compartment space, which is almost always empty. We can safely subtract a further 5%. Rational use of space for the driver and passenger is reached, if to cut off all "unnecessary parts". The result is a 2 seater car slightly larger than the Renault Twizy, with 2 full seats with plenty of space for comfort and safety, but no luggage compartment.
Analogues. Renault Twizy, Volpe. Similar rental systems (at the time of design, 2014): Autolib; Europcar, Budget, Sixt, Hertz, Avis.