Abstract <p>The most pressing issue of the present era is air pollution, and we can use the air pollution tolerance index to determine the degree of tolerance of lichens. This study is the first to apply the index to lichens, making it a pioneering effort. In the town of Darjeeling, where heavy motor traffic from tourism is a significant cause of air pollution, the stretch along the Hill Cart Road from DM Bungalow to Batasia was selected as the polluted area. We chose Bhutia Busty as the control area as there was no vehicular pollution and less anthropogenic activity. We studied eight lichen species at both the control and polluted sites. Various parameters recorded different tolerant trends among the species, indicating different adaptive modes to cope with the same pollution stress. Classification based on APTI values established distinct tolerance levels among species, with <i>Cladonia fenestralis</i> and <i>Cladonia didyma</i> showing the highest tolerance. Cluster analysis illustrated ecological niches and adaptive strategies. Moreover, statistical analyses verified the significance of the findings, corroborating lichens’ dynamic responses to pollution-induced stress. This research advances our understanding of lichen-environment interactions in polluted urban environments, providing insights into environmental management and conservation strategies.</p>