Why and how to improve air quality in urban transport

Improves passenger health and comfort

Every day, millions of citizens spend a significant portion of their time on buses, trams, and other forms of urban surface transport. These vehicles, which are the backbone of mobility in our cities, paradoxically operate at the heart of the source of pollution: road traffic. This makes them ‘bubbles’ that move immersed in an outdoor environment laden with emissions, presenting a unique challenge to the air quality breathed by both passengers and drivers.

The reason for monitoring lies in a dual source of pollution. On the one hand, there is infiltration from the outside. Despite enclosure systems, exhaust gases from other vehicles — especially nitrogen oxides (NOx) and fine particles (PM2.5) — penetrate the interior, reaching concentrations that often exceed street levels. On the other hand, there are internal sources of emissions. The high density of passengers in a small, confined space causes a rapid increase in carbon dioxide (CO2) levels, leading to drowsiness and a perception of ‘stale’ air. In addition, the vehicle's own materials (upholstery, plastics) can release volatile organic compounds (VOCs), and the presence of many people increases the bioaerosol load, facilitating the transmission of viruses.

This is where the advantages of continuous monitoring come into play. Installing CAI sensors in the urban transport fleet offers tangible and immediate benefits. The main advantage is the protection of the health of users and workers, who are exposed on a daily and prolonged basis. Secondly, it enables intelligent ventilation management. Instead of operating air conditioning systems constantly and inefficiently, they can be activated or boosted automatically only when sensors detect that CO₂ or PM₂.₅ thresholds are exceeded. This translates into crucial energy savings, a particularly relevant factor in electric bus fleets, where every kilowatt saved increases the vehicle's range. Finally, providing data on air quality improves the passenger experience and confidence, positioning the operating company as a responsible entity committed to the well-being of its customers.