It is annoying to be driving behind a truck especially one that smells of diesel combustion products. Doing something about that is desirable but it will come at a tremendous cost. trucks are bought and used for years. It is not something that you replace quickly because it is costly. A common trend in environmental reporting is to put things in terms of jobs vs. the environment. For the port cities such as LA environmental protection has become more important than jobs. Once upon a time a new truck might cost $20,000. Now they are six figures which hurts the small independent truckers in particular.