The given line graph displays the amount of nitrogen oxide emissions produced by four distinct types of vehicles travelling at different speeds.
Overall, the petroleum and diesel cars emitted a very stable amount of nitrogen oxide at any surveyed speed. In constrast, the amounts of nitrogen oxide emitted in lorries and buses followed a similar trajector, with a dip in average speeds and a surge at very high speeds.
Looking first at the two vehicles discharging unstable amounts, buses and lorries discharged a signficantly larger amount of nitrogen emissions. As the speed increased from 10 to 60 to 130 kph, the amount of buses decreased from 40 to only 25 g/km before rebounding steadily to more than 40 g/km at the following speed. Following a similar pattern, the amounts of nitrogen oxides emitted by lorries witnessed a significant decrease from 35 to 20 g/km in the first 80 kph before going upward again and reaching around 25 g/km at the end of the surveyed speed.
Smaller vehicles, on the other hand, were observed with a much more stable discharge of nitrogen oxide emissions. At any speed, a car running on petroleum and diesel car released around 10 and 5 g/km of nitrogen oxide emissions, respectively.
