Roadside Plant Species and Their Role in Traffic-Pollution Mitigation: An Indian Perspective

Abstract

Rapid urbanization, increasing road traffic, and expansion of transport infrastructure have intensified air-pollution problems in Indian cities. Vehicular activity contributes directly and indirectly to particulate matter (PM), nitrogen oxides (NOₓ), carbon monoxide (CO), volatile organic compounds (VOCs), black carbon, and metal-containing road dust. Roadside vegetation represents a comparatively low-cost nature-based intervention capable of intercepting particulate matter, absorbing selected gaseous pollutants, modifying local airflow, reducing resuspended dust, and providing additional ecosystem services. However, the effectiveness of roadside vegetation depends strongly on plant species, leaf morphology, canopy structure, vegetation density, meteorological conditions, road geometry, and the surrounding urban form. This review examines the role of roadside plant species in mitigating traffic-related pollution with particular emphasis on Indian cities. Evidence from studies conducted in Delhi, Pune, Bathinda, Kanpur, Varanasi, Lucknow, Uttarakhand and other Indian locations is synthesized. Species such as Ficus benghalensis, Ficus religiosa, Mangifera indica, Delonix regia, Polyalthia longifolia, Azadirachta indica, Saraca asoca, Grevillea robusta, Millettia pinnata, Terminalia arjuna, Nerium spp. and other locally adapted species have demonstrated varying degrees of pollution tolerance and pollutant accumulation. Particular attention is given to leaf traits, Air Pollution Tolerance Index (APTI), Anticipated Performance Index (API), particulate deposition, heavy-metal accumulation, physiological responses, and the design of vegetation barriers. The review emphasizes that roadside plantation should not be based simply on the number of trees planted; rather, species selection and spatial configuration should be integrated with traffic intensity, street geometry, pollutant characteristics, local climate, pedestrian exposure, and maintenance requirements. Vegetation should complement—not replace—emission reduction, public transport, road-dust management, and regulatory measures. A species-selection framework for Indian urban roads is proposed, together with research priorities involving standardized PM-removal measurements, native species evaluation, plant–pollutant interactions, and city-specific vegetation planning.