The line chart compares the amount of nitrogen oxide emitted from four different types of vehicles.
Overall, buses consistently release the largest nitrogen oxide emission regardless of their speed. Additionally, according to the increasing velocity, the level of emission exhibits strong fluctuations across buses and lorries, whereas those of petrol cars and diesel cars almost remain unchanged.
Regarding buses and lorries, buses emit around 40 g/km at the speed of 10 kph, emerging as the highest amount compared to other vehicles. However, not until reaching the speed of 60 kph, this figure hits the lowest point at nearly 25 g/km, and then it rises sharply to approximately 43 g/km at 130 kph. In contrast, the figure for lorries initially stands at about 33 g/km at 10 kph, after which it drops significantly and hits the bottom at about 16 g/km at 90 kph. This data then grows slightly by around 9 g/km at 130 kph.
Concerning the remaining categories, diesel cars seem to be the most environmentally friendly automobiles among the others, with its amount of emissions almost remaining constantly at around 5 g/km at any velocity. Similarly, that of petrol cars almost follows the comparable trend, albeit at a much higher level (at roughly 10 g/km).