How many cars do we really need? Evaluating the impact of full-scale shared vehicle systems in Montreal and Quebec

This study refines and expands a simulation-based approach to estimate the number of vehicles required to meet the automobile travel demand of all residents in the Montréal and Québec City metropolitan regions—under the hypothetical scenario of a full-scale shared vehicle system. The model assumes no vehicle repositioning and maintains the same total volume of vehicle-kilometers traveled as in current conditions.

Using origin–destination survey data and time-of-day travel patterns, the simulation evaluates fleet requirements under varying assumptions about users’ willingness to walk to access a shared vehicle. Scenarios explore maximum walking distances (e.g., 300 m, 500 m, 800 m) to assess how spatial flexibility influences fleet size and system efficiency.

Beyond fleet sizing, the study estimates key societal and environmental benefits:

-Parking space savings, due to reduced vehicle ownership and idle time;

-Financial savings, from avoided costs of vehicle purchase, maintenance, and insurance;

-Energy savings, assuming a more efficient shared fleet with optimized usage.

Simulations conducted in Montréal using data from the 2008 Origin–Destination survey showed that 27% of household-owned vehicles were not necessary to support daily car trips, and that private vehicles were parked 95% of the time. Depending on the access distance assumption, results suggested that 41% to 52% of vehicles could be eliminated while maintaining full coverage of automobile trips. At the time, economic benefits had not been estimated.

This updated study aims to revisit the simulation with refined assumptions and to introduce new estimations of both individual and collective financial impacts. These include avoided costs related to vehicle ownership, maintenance, and insurance, as well as potential savings in urban space due to reduced parking needs. The energy footprint of travel could also be reduced, particularly with the deployment of a sober fleet of electric or hybrid vehicles.

Future extensions will incorporate modal shift scenarios, redirecting short trips to active modes and longer trips to high-performance transit corridors. These refinements will help assess the full potential of shared mobility systems when integrated with broader sustainable transport strategies.