to demonstrate the durability of the emissions control system and to establish the emissions deterioration. Emissions are measured at three points during the DF test (125 hours, midpoint, and end of test) on the FTP and RMC. Following testing, all data are submitted to EPA as part of the application for certification.

Following certification and production, an enforcement process is in effect. EPA can come into the production facility and perform a Selective Enforcement Audit. It can sequester 25 to 30 engines and start an audit process under which five of these engines must be under the emission standards as measured on the FTP and RMC after a 125-hour conditioning period. If failures occur, a statistical process is used that may require all (25 to 30) engines to be tested. EPA can also do in-use emissions testing on vehicles in regular service. This testing is done using a Portable Emission Measurement System either over-the-road or on a chassis dynamometer. Emissions are measured over a 30-minute period (constantly updating) and a determination is made as to whether emissions are exceeding the not-to-exceed values (usually either 125 or 150 percent of the regulated values depending on the engine family).

Compliance flexibility is provided with averaging, banking, and trading, which can take place among engine families or with other manufacturers. Also, a provision to pay non-compliance penalties is available if the manufacturer wants to certify to an emissions level higher than the standard.

A chassis cycle or schedule may be used for the emissions certification of certain Class 2B vehicles as an alternative to the heavy-duty engine dynamometer procedure. Historically, the Class 2B vehicle manufacturer was also the manufacturer of the engine, because Class 2B vehicles were gasoline powered and usually produced by a light-duty-vehicle manufacturer. EPA Tier 2 light-duty emissions requirements were extended to include medium-duty passenger vehicles, which are between 8,501 and 10,000 lb gross vehicle weight (GVW) and may include diesel-powered vehicles. The EPA’s 2006 regulatory announcement (EPA, 2006b) explains that larger sport utility vehicles and vans (8,501- to 10,000-lb GVW) will require light-duty-style fuel economy measurements from 2011. California’s Low Emission Vehicle (LEV II) regulations cover emissions from vehicles in the 8,501- to 14,000-lb range through chassis testing. A federal option also exists for chassis testing of vehicles up to 14,000 lb GVW.

EPA began regulation of nonroad engines in the mid-1990s, with regulations now covering the immense range from handheld spark ignition engines (such as leaf blowers) to locomotive engines. Stated by EPA as being one of the most complex sets of emissions regulations undertaken, the certification process focuses again on the engine only, tested over prescribed cycles or steady-state modes. The engines are divided into many classes depending on the size and type of use, and test cycles are prescribed for each class.

Heavy-duty vehicle regulations can be complex; however, there are examples of compliance mechanisms that provide flexibility and minimize the burden on industry. An illustrative example is performance-based Federal Motor Vehicle Safety Standard (FMVSS) 121, which requires that a vehicle stop within a certain distance from an initial speed when loaded to the GVW rating (Table 3-2). The stopping distance is dependent on vehicle type. For example, from an initial speed of 60 mph, truck tractors must stop within 355 ft, single-unit trucks within 310 ft, and buses within 280 ft (NHTSA, 2004). This example illustrates clearly that regulatory requirements can differ for the various vehicle types within the general class of heavy-duty vehicles.

The brake performance evaluation of trailers is carried out differently than for trucks and buses in that, because they are not self-powered, trailers have a dynamometer requirement rather than a test track requirement (NHTSA, 1990). This illustrates that the test methods for a given heavy-duty vehicle regulation can vary significantly depending on the vehicle unit (e.g., truck-tractors or trailers).

Because the heavy-duty truck market is so complex, and many of the vehicles are custom-built (as discussed in Chapter 2), regulations applied at the final stage of manufacture can pose a heavy burden on the manufacturer. However, this burden can be lessened by “type approval” at the component level. For example, in the case of brake regulations, truck axle manufactures supply brakes with the axle assemblies properly sized and rated for the load that the axle is designed to carry. By using these axles the final-stage manufacturer can assure compliance with the brake regulations without