Which of the following statements is true about diesel engine emissions trend over recent years?

• A. They have significantly reduced.
• B. They have significantly increased.
• C. They have stayed the same.
• D. They fluctuated unpredictably.

Answer: (A)

Diesel engine emissions have fallen significantly in recent years thanks to tighter regulations and advances in technology. Modern diesels use diesel particulate filters to trap soot, and selective catalytic reduction systems (often with AdBlue) to convert nitrogen oxides into harmless nitrogen and water. Exhaust gas recirculation lowers combustion temperatures, and improvements in high-pressure common-rail fuel injection, combustion efficiency, and fuel quality further reduce pollutants. Regulatory standards such as Euro 5/6 in Europe and various Tier/US standards have pushed manufacturers to adopt these technologies, driving big reductions in both particulate matter and NOx for new vehicles. While real-world driving can show some variability compared to lab tests, the overall trend across major markets is a substantial decline in diesel emissions.