The line graph compares the amount of nitrogen oxide emitted by four different vehicles (buses, lorries, petrol cars, and diesel cars) in terms of their speed. Units are measured in g/km.
Overall, diesel and petrol cars emit nearly equal amounts of nitrogen oxide at any speed, being the least polluting among the examined transports. Buses stand out among others with their considerably higher numbers, whereas they pollute the air less when they reach 60 kph.
In general, buses emit 40 g of nitrogen oxide per km when their speed is 10 kph, but this number decreases to just over 26g when they accelerate their speed until 60 km/h. Interestingly, at higher speeds, buses release more and more nitrogen oxide, emitting 42g when they reach 130 kph.
The figure for lorries shows 33 g of nitrogen oxide at the slowest speed, and then it reduces to 18 g as soon as they speed up to 90 kph. When lorries run at 130 kph, they release a lower amount of nitrogen, emitting 25 g per km.
In contrast, the figure for petrol cars accounts for more or less 10 g of nitrogen oxide regardless of their speed. Lastly, diesel cars are reported to be the most eco-friendly modes of transport among others, releasing just over 5 g of nitrogen oxide each km.