The triple-win potential of sustainable mobility

Shifting daily commutes from private cars to walking, cycling, or public transit can simultaneously reduce household expenses, ease pressure on public budgets, and mitigate social and environmental externalities. Using an origin-destination survey combined with administrative data for Quebec, this study develops an integrated cost-benefit framework to evaluate modal-shift scenarios. Results indicate that up to one-third of car commutes in the province's largest metropolitan area (Montreal) could potentially shift to sustainable alternatives, generating annual public savings of about CAD 1.2 billion, reduced external costs of CAD 2.5 billion, and lower commuting-related carbon emissions by 12 percentage points. Extending the analysis to the provincial level doubles total savings to nearly CAD 7 billion per year and cuts total carbon emissions by roughly 1 p.p. Modest active mobility infrastructure upgrades along key routes could unlock about 20% of this potential, while achieving the full triple-win will require more ambitious and coordinated policies. • Modal shifts to active and public transportation reduce private, public, and external costs. • Walking and cycling save up to $0.07 per dollar spent, while driving costs $0.78. • Shifting car trips under 5–10 km could cut Quebec's annual GHG emissions by 1%. • These shifts could save $4–$7 billion annually, including $1.8–$3.4 billion in external costs. • Modest active mobility infrastructure upgrades could unlock about 20% of this potential. • Achieving the full triple-win will require coordinated policies targeting infrastructures and behaviors.