Regulatory Background on the U.S. Mobile Source Emission Control Program

U.S. EPA Tier 3 and California LEV III Rulemakings

California adopted their LEV III light-duty vehicle emission standards in 2012.  LEV III will further reduce vehicle emission limits to a fleet average level consistent with California’s current LEV II SULEV exhaust emission limit (and EPA’s Tier 2, Bin 2 exhaust emission limit) by 2025.  LEV III implementation will begin with the 2015 model year.  The LEV III criteria pollutant regulation was rolled out as part of the state’s Advanced Clean Cars Program that also includes greenhouse gas (GHG) standards for the 2017-2025 model years, as well as revised zero-emission vehicle (ZEV) requirements.

EPA finalized a similar set of criteria emission regulations in 2014 as part of a Tier 3 regulatory package with which California has largely harmonized after adopting amendments to their LEV III program in 2014.  EPA’s Tier 3 regulatory program has slightly delayed implementation dates relative to LEV III, beginning with the 2017 and 2018 model years for lighter and heavier light-duty vehicles, respectively.  In addition to tighter emission standards for hydrocarbons, CO, and NOx, LEV III and the Tier 3 regulations tighten emission standards for particulates and evaporative emissions from future light-duty vehicles.  The Tier 3 emissions program is also aligned with and implemented over the same time frame as the U.S. EPA’s GHG emission standards for light-duty vehicles starting in the 2017 model year.  The harmonization of the federal and California regulations will, for the first time, allow automobile manufacturers to comply with one set of standards across all 50 states.

The primary strategy employed to reduce emissions from future light-duty vehicles under the LEV III regulation is to phase in PZEV-type exhaust and evaporative emission technologies across the entire light-duty and medium-duty fleet by 2025.  The individual NMOG and NOx limits were combined under LEV III and Tier 3 to provide vehicle manufacturers additional flexibility in employing strategies to meet the combined limit values rather than individual limits under LEV II or Tier 2.  By 2025, when it is fully implemented, LEV III will result in a 75% reduction in NMOG plus NOx emissions across the California fleet whereas the federal fleet achieves an 80% reduction in NMOG+NOx and 70% reduction in PM with Tier 3.

The phase-in for the requirements is slightly different for passenger cars and smaller light-duty trucks (LDT1) versus larger LDT2 SUVs and pick-up trucks.  The phase-in schedule for the combined fleet average emission limits is shown in Figure 1 with both curves converging on a SULEV limit of 0.030 g/mi NMOG+NOx in 2025.  A more detailed picture of all of the combined NMOG+NOx and CO emission limits for the certification classifications that manufacturers must meet as a part of these rules is laid out in Table 1.  The federal Tier 3 standards for LDVs, LDTs, and MDPVs up to 10,000 lbs. GVWR are classified into seven Bins designated from Bin 0 to Bin 160 where the numerical value corresponds to the NMOG+NOx milligram limit (Bin 0 is not included in Table 1).  The fleet average required from the Tier 3 standards matches the two curves in Figure 1 starting in the 2017 model year.

As a way to force new emission control technologies and provide manufacturers with greater flexibilities in meeting the average emission limits in Figure 1, ARB added three new emission certification categories, including one below SULEV (SULEV20) and two between SULEV and ULEV (ULEV50 and ULEV70).  The numerical designations refer to the combined NMOG+NOx emission limit, in mg/mile, associated with each vehicle certification category.  Eliminated under LEV III is the intermediate 50,000-mile emission standards and an increase of the full useful life (FUL) durability requirements from 120,000 to 150,000 miles for all vehicle classifications under the program.

The Tier 3 program includes 120,000-mile FUL certification for the lighter vehicles (<6,000 lbs. GVWR); however, the emission limits are lowered by a corresponding 15% (a manufacturer may also choose to certify these lighter vehicles to the 150,000-mile standards).  The federal Tier 3 mandatory emissions warranty remains at 8 years or 80,000 miles which is the same as under Tier 2 (7 years or 70,000 miles for California LEV II and LEV III).  Under both programs, a manufacturer can receive a 5 mg/mile NMOG+NOx credit for offering a full 150,000-mile warranty.

Table 1. California LEV III/EPA Tier 3 150,000-Mile Exhaust Emission Limits

Vehicle Class Certification Level NMOG+NOx (mg/mi) CO (g/mi)
(up to 10,000 lbs. GVWR for MDPVs; up to 8500 lbs. GVWR for PCs, LDTs)
LEV160/Bin160 160 4.2
  ULEV125/Bin125 125 2.1
  ULEV70/Bin70 70 1.7
  ULEV50/Bin50 50 1.7
  SULEV30/Bin30 30 1.0
  SULEV20/Bin20 20 1.0
MDVs (8501-10,000 lbs.
LEV395/Bin395 395 6.4
  ULEV340/Bin340 340 6.4
  ULEV250/Bin250 250 6.4
  ULEV200/Bin200 200 4.2
  SULEV170/Bin170 170 4.2
  SULEV150/Bin150 150 3.2
MDVs (10,001-14,000 lbs. GVWR) LEV630/Bin630 630 7.3
  ULEV570/Bin570 570 7.3
  ULEV400/Bin400 400 7.3
  ULEV270/Bin270 270 4.2
  SULEV230/Bin230 230 4.2
  SULEV200/Bin200 200 3.7

The LEV III and Tier 3 programs also establish more stringent limits on medium-duty vehicles (MDVs) up to 14,000 lbs. GVWR starting with the 2016 model year under LEV III and 2018 for Tier 3.  Tier 3 classifies vehicles in the 8,501 to 14,000 lb. GVWR range as heavy-duty and offers voluntary standards starting in 2016 that are available for early credits.  By 2022, manufacturers are required to certify 90% of these respective weight class vehicles to SULEV170 or SULEV230 and 10% to ULEV250 and ULEV400, respectively.  Federal Tier 3 standards retain analogous Bin classification for the heavier vehicles with corresponding milligram per mile designations (see Table 1 for MDV emission certification categories).  Furthermore, all MDVs in the 8501-10,000 lb. GVWR weight class must certify on a chassis dynamometer starting with the 2020 model year, which will facilitate the ability to perform in-use compliance on these heavier vehicles. 

With the expectation that direct injection technology will be rolled out over a larger portion of the gasoline light-duty fleet, ARB established more stringent particulate matter (PM) limits for light- and medium-duty vehicles.  For light-duty vehicles, a 3 mg/mi FTP PM standard begins in 2017 for both LEV III and Tier 3, and is fully phased-in by 2021 for LEV III and by 2022 for Tier 3.  The LEV III regulations continue to tighten to a 1 mg/mi FTP PM limit that begins in 2025 with a four-year phase-in across the fleet.  MDVs (8500-10,000 lbs.) will need to meet an 8 mg/mi FTP PM standard and the heavier MDVs (10,000-14,000 lbs.) a 10 mg/mi standard starting in 2017 (fully phased in by 2021). 

LEV III and Tier 3 include full useful life standards for the supplemental federal test procedure (SFTP), including extending these standards to MDVs.  LEV II has only a 4,000-mile SFTP requirement for light-duty vehicles.  The gaseous criteria pollutants are tested over the SC03 and US06 test cycles that reflect more aggressive driving (US06) and air conditioner operation (SC03).  Both programs include SFTP PM standards of 6 mg/mile over the US06 test cycle for passenger cars and LDT1 vehicles (this SFTP PM limit is set at 10 mg/mile for 2017 and 2018), and 20 mg/mi for LDT2s and MDVs up to 14,000 lbs. GVWR. 

LEV III extended PZEV-type, near-zero evaporative emission requirements to all light-duty vehicles by 2022.  Manufacturers have two compliance options that include a zero evap-based fuel system test and a 2-day and 3-day + hot soak whole vehicle test in a Sealed Housing for Evaporative Determination (SHED) apparatus.  OEMs have the option to certify to a running loss standard (50 mg/test limit), a whole vehicle standard, and use the existing fuel system rig test to show that their fuel system emissions are at near-zero grams (0.054 g/test) per test and meet a 2-day + hot soak & 3-day + hot soak SHED whole vehicle limits of 350 mg/test for passenger cars, 500 mg/test for LDT1s, 750 mg/test for LDT2s, MDPVs, MDVs, and HDVs (over 14,000 lbs. GVWR).

The other option allows OEMs to certify to a running loss standard of 50 mg/test, a tighter fleet average whole vehicle standard based on the 2-day + hot soak & 3-day + hot soak SHED test.  Under this option, the whole vehicle fleet average limits are 300 mg/test for passenger cars and LDT1s, 400 mg/test for LDT2s up to 6,000 lbs. GVWR, 500 mg/test for heavier LDT2s and medium-duty passenger vehicles (MDPVs), and 600 mg/test for MDVs and HDVs.  Rather than performing a complete fuel system rig test, under this option, manufactures are allowed to meet canister emission limits using a simplified, canister bleed emission test protocol.  Canister bleed emission limits are set at 20 mg/test for smaller vehicles up to 10,000 lbs. GVWR and 30 mg/test for MDVs and HDVs.   

The U.S. EPA has included a similar set of evaporative standards as part of their Tier 3 program with only a few minor differences.  The standards represent a 50% reduction from Tier 2 levels.  The federal standards are identical to the Option 2 requirements under LEV III; however, manufacturers may use the LEV III Option 1 standards for vehicles certified prior to 2017.  The FUL is extended to 150,000 miles.  As under LEV III, an identical canister bleed emission standard and test method is included in Tier 3.  EPA and ARB have also added a leak test and emission standard to ensure that the cumulative equivalent diameter of any leak does not exceed 0.02 inches anywhere in the fuel and evaporative control system.  This leak test is also being included in the In-Use Verification Program, establishing in-use requirements for evaporative emissions for the first time. 

Both California and EPA will migrate to an E10 certification fuel for LEV III and Tier 3 to better represent the fuels that will be available across the country.  EPA has included a new E85 test fuel for flex fuel vehicles (FFVs).  As with other recent federal emission regulations such as Tier 2 and the 2007/2010 on-road heavy-duty diesel standards, the Tier 3 standards include new sulfur limits on gasoline with a 10 ppm average value beginning in 2017 (California gasoline sulfur levels were capped at 20 ppm in 2012).  The federal gasoline sulfur cap will remain at the current cap of 80 ppm sulfur.  To achieve the average value of 10 ppm will require that most of the gasoline produced must remain very close to the average value.  The tighter gasoline sulfur standard is expected to reduce NOx emissions in the existing fleet of vehicles by 20-30% due to a reduction in sulfur poisoning of the catalyst while making it easier for new vehicles to meet the tighter NOx+NMOG limits under the Tier 3 regulations.

Both LEV III and Tier 3 tailpipe and evaporative emission regulations include a number of phase-in flexibilities, credit and allowance programs, hardship provisions and more lead time for small volume manufacturers that produce less than 5,000 vehicles per year.  The 10 ppm fuel sulfur standard for gasoline under Tier 3 also includes an averaging, banking, and trading program for refiners to spread out their capital investments. 

Additional details of California’s LEV III program are available at:  Details for EPA’s Tier 3 program can be found at: