  Alternative routing is crucial to minimize the environmental impact of urban
transportation while enhancing road network efficiency and reducing traffic
congestion. Existing methods neglect information about road popularity,
possibly leading to unintended consequences such as increasing emissions and
congestion. This paper introduces Polaris, an alternative routing algorithm
that exploits road popularity to optimize traffic distribution and reduce CO2
emissions. Polaris leverages the novel concept of K-road layers, which
mitigates the feedback loop effect where redirecting vehicles to less popular
roads could increase their popularity in the future. We conduct experiments in
three cities to evaluate Polaris against state-of-the-art alternative routing
algorithms. Our results demonstrate that Polaris significantly reduces the
overuse of highly popular road edges and traversed regulated intersections,
showcasing its ability to generate efficient routes and distribute traffic more
evenly. Furthermore, Polaris achieves substantial CO2 reductions, outperforming
existing alternative routing strategies. Finally, we compare Polaris to an
algorithm that coordinates vehicles centrally to distribute them more evenly on
the road network. Our findings reveal that Polaris performs comparably well,
even with much less information, highlighting its potential as an efficient and
sustainable solution for urban traffic management.
