When did emissions testing regulations start for diesel vehicles?

The correct answer is 1998 because that is the year when emissions testing regulations specifically for diesel vehicles were initiated as part of broader efforts to reduce air pollution. The implementation of these regulations aimed to address increasing concerns regarding the environmental impact of diesel emissions, which are known to contain harmful pollutants that can adversely affect air quality and public health.

Prior to 1998, while there were regulations in place for gasoline vehicles, the enforcement of emissions standards for diesel vehicles was not as robust. In establishing these standards for diesel, regulatory agencies sought to ensure that all types of vehicles contributed to cleaner air initiatives, reinforcing the importance of emissions testing across various fuel types.

In the years following 1998, regulations have continued to evolve, with further updates and stricter standards introduced to continually address the challenges posed by diesel emissions.