Urban Congestion Relief Experiments through Routing-app Interventions

Traffic congestion remains a persistent challenge for urban mobility, increasing travel delays and elevating CO2 emissions. The widespread use of smartphones and GPS navigation creates new opportunities to mitigate congestion through routing optimizations in apps, yet real-world evidence for the effectiveness of such interventions is limited. Here we report large-scale empirical experiments evaluating routing-based traffic interventions on ~100 highly congested road segments across 10 major US cities. By rerouting a small share of Google Maps trips from targeted congested highway and arterial segments to less congested alternatives of equivalent road-classes with comparable travel times, we observe a city-average 2% increase in vehicle speeds on the intervened segments, along with improved travel times 0.7% and potential annual reductions exceeding 1,000 tons of CO2-equivalent emissions per city in the majority of studied locations. These findings provide evidence that marginal routing interventions involving a small proportion of vehicles can measurably enhance overall road network efficiency, offering a practical pathway to easing congestion and advancing urban sustainability.