Center for Environmental Research & Technology

Engines used in heavy-duty trucks are certified in laboratories and separate from the truck chassis and the "real world" in which they operate, because most diesel engines are designed to work in multiple applications. This approach leads to significant uncertainties in estimating the actual emissions that diesel engines produce under "real-world" operating conditions.

In response to these uncertainties, the U.S. Environmental Protection Agency and other research organizations have attempted to develop systems capable of measuring emissions from heavy-duty vehicles while on the road, or under conditions representative of "real-world" driving. These alternatives fall into three major categories:

• Heavy-duty chassis dynamometers. These laboratories follow the CFR methods and usually are fixed laboratories, although West Virginia University operates a portable dynamometer laboratory.
• Portable on-road emissions systems. These generally are suitcase-sized units that extract a sample from the truck's exhaust pipe and quantify emissions in the raw exhaust.
• Trailer-based emissions laboratories. The U.S. EPA completed development of an emissions laboratory contained within a trailer in the late-1990s, but it was not designed to replicate the CFR standards.

CE-CERT's heavy-duty mobile laboratory represents a significant step forward in "real world" emissions measurement capability. We have installed a complete emissions laboratory based on the CFR standards, including a full dilution tunnel, within a 53-foot over-the-road trailer. The trailer connects to a class 8 truck's fifth wheel and serves as the load for the truck to pull. A connector captures the truck's entire exhaust stream and transfers it into the laboratory, where gaseous, toxic, and particulate emissions are quantified. The mobile lab can be operated in "real-world" traffic conditions or over standardized testing cycles.