The provided pie chart illustrates the distribution of nitrogen oxide (NOx) emissions across different categories of road transport in London for the year 2020. Overall, the data reveals a pronounced imbalance in the contribution of various vehicle types to this form of air pollution, with certain categories being disproportionately responsible for the majority of emissions.
The most striking feature is the overwhelming dominance of taxis and heavy goods vehicles (HGVs). Despite likely representing a relatively small proportion of total vehicles on the road, these two categories together account for a staggering 70% of London’s transport-related NOx emissions. Specifically, taxis alone are responsible for 35% of the total, making them the single largest contributor. HGVs follow closely, generating another 35%. This highlights the outsized impact of commercial and freight transport, which typically involve diesel engines and higher mileage within urban areas, on air quality.
In contrast, the contribution from cars is surprisingly lower, constituting only 20% of NOx emissions. This is a notable finding, given that private cars typically make up the vast majority of vehicles in a city. This comparatively lower share may reflect a combination of factors, including a larger fleet of newer, cleaner petrol and hybrid vehicles, as well as the significant progress in reducing emissions per vehicle from this category compared to older diesel technologies still prevalent in some commercial fleets.
The remaining 10% of emissions are attributed to buses and coaches, and motorcycles. The share for buses and coaches is relatively modest, which may be indicative of London’s efforts to modernise its public transport fleet with cleaner, hybrid, and electric buses. Motorcycles contribute the smallest slice, which aligns with their smaller engine sizes and lower total numbers.
In summary, the 2020 data presents a clear dichotomy. While private car use is widespread, its relative contribution to NOx pollution is eclipsed by that of commercial transport, particularly taxis and HGVs. This suggests that targeted policy interventions – such as accelerating the shift to zero-emission taxis, implementing stricter low-emission zones for freight vehicles, and continuing to electrify the bus fleet – would be the most effective strategy for significantly reducing NOx concentrations in London. The chart underscores that solving urban air pollution is less about the number of vehicles and more about addressing the specific, high-impact sectors within the transport ecosystem.