California emission standards have been traditionally more stringent than the EPA requirements, but their structure is similar to that of the federal legislation. The major regulatory steps in the evolution of California emission standards include:

  • Tier 1/LEV California emission standards extended through the year 2003.
  • LEV II California regulations were phased-in through model years 2004-2010.
  • LEV III California regulations are phased-in through model years 2015-2025.

A number of other states have adopted California LEV II emission standards.

Low Emission Vehicle (LEV) Standards

These California emission standards, which applied through model year 2003, were expressed using the following emission categories:

  • Tier 1
  • Transitional Low Emission Vehicles (TLEV)
  • Low Emission Vehicles (LEV)
  • Ultra Low Emission Vehicles (ULEV)
  • Super Ultra Low Emission Vehicles (SULEV)
  • Zero Emission Vehicles (ZEV)

Car manufacturers were required to produce a percentage of vehicles certified to increasingly more stringent emission categories, according to schedules based on vehicle fleet emission averages for each manufacturer. After 2003, Tier 1 and TLEV standards were eliminated as available emission categories.

The same standards for gaseous pollutants applied to diesel- and gasoline-fueled vehicles. PM standards applied to diesel vehicles only. Emissions were measured over the FTP-75 test and are expressed in g/mile. The additional SFTP procedures were phased-in in California between 2001 and 2005.

Table 1
LEV Emission Standards for Light-Duty Vehicles, FTP-75, g/mi
Category50,000 miles/5 years100,000 miles/10 years
Passenger cars
LDT1, LVW <3,750 lbs
LDT2, LVW >3,750 lbs
Tier 10.324.40.70.08-0.405.50.97--
a - NMHC for all Tier 1 standards

  LVW - loaded vehicle weight (curb weight + 300 lbs)
  LDT - light-duty truck
  NMOG - non-methane organic gases
  HCHO - formaldehyde

Emission standards for medium-duty vehicles are summarized in Table 2.

Table 2
LEV Emission Standards for Medium-Duty Vehicles, FTP-75, g/mi
Category50,000 miles/5 years120,000 miles/11 years
MDV1, 0-3750 lbs
MDV2, 3751-5750 lbs
Tier 10.324.40.7--0.466.40.980.10-
MDV3, 5751-8500 lbs
Tier 10.395.01.1--0.567.31.530.12-
MDV4, 8501-10,000 lbs
Tier 10.465.51.3-0.0280.668.11.810.12-
MDV5, 10,001-14,000 lbs
Tier 10.607.02.0--0.8610.32.770.12-
a - NMHC for all Tier 1 standards

  MDV - medium-duty vehicle (the maximum GVW from 8,500 to 14,000 lbs). The MDV category is divided into five classes, MDV1 .. MDV5, based on vehicle test weight. The definition of “test weight” in California is identical to the Federal ALVW.
  NMOG - non-methane organic gases
  HCHO - formaldehyde

Low Emission Vehicle II (LEV II) Standards

In November 1998, the California ARB adopted LEV II emission standards which were phased-in from 2004 through 2010. Manufacturers may certify vehicles to LEV II emission standards (categories) until model year 2019.

Under the LEV II regulation, the light-duty truck and medium-duty vehicle categories of below 8500 lbs gross weight were reclassified and had to meet passenger car requirements, as shown in Table 3. As a result, most pick-up trucks and sport utility vehicles (old MDV4 and MDV5) were required to meet the passenger car emission standards. The reclassification was phased-in by the year 2007.

Three sets of increasingly more stringent emission standards were defined: LEV, ULEV, and SULEV. A fourth emission category, PZEV (partial zero emission vehicle), had the same test emission levels as SULEV, but also included a “zero” evaporative emissions standard and a 150,000 mile/15 years emission durability. LEV II emission standards for FTP-75 testing are summarized in the following tables (additional SFTP standards are also applicable).

Table 3
LEV II Emission Standards for Passenger Cars and LDVs < 8500 lbs (LDT1 & LDT2), FTP-75, g/mi
Category50,000 miles/5 years120,000 miles/11 years
Table 4
LEV II Emission Standards for Medium Duty Vehicles, Durability 120,000 miles, FTP-75, g/mi
8,500 - 10,000 lbs LEV0.1956.
10,001 - 14,000 lbs LEV0.2307.

Under the LEV II legislation, NOx and PM standards for all emission categories were significantly tightened compared to the LEV levels. The same standards applied to all vehicles regardless of fuel (under revisions adopted on November 15, 2001 gasoline vehicles have been no longer exempted from the PM standard). Light-duty LEVs and ULEVs certified to a 0.05 g/mi NOx standard, phased-in starting with the 2004 model year. A full useful life PM standard of 0.010 g/mi was introduced for light-duty vehicles and trucks less than 8500 lbs GVW certifying to LEV, ULEV, and SULEV standards. Therefore, the LEV II emission standards could only be met by vehicles with advanced emission control technologies. In the case of diesels, vehicles typically required particulate filters and NOx reduction catalysts.

Fleet Emission Requirements. LEV II standards required automakers to reduce their vehicle fleet emission levels each year through 2010—the last year of the LEV II phase-in period. In the case of light-duty vehicles, manufacturers had to meet increasingly tighter fleet average NMOG standards. For example, the final (2010) LEV II fleet average NMOG standard was 0.035 g/mi for PC/LDT1 and 0.043 g/mi for LDT2. Medium-duty vehicles had no fleet average standards, but manufacturers were required to certify increasing percentages of their MDVs to the applicable emission standards. Evaporative emission standards were also increasingly tightened through 2010.

While the California LEV II program was similar in structure to the federal Tier 2 legislation, there were a number of differences regarding overall fleet emission stringency, durability, and categorization of vehicles. One difference is that the federal approach uses eight certification “bins” (with Tier 2 Bin 5 being similar to California’s LEV, and Tier 2 Bin 2 similar to SULEV) to allow averaging across a greater level of emission diversification in the fleet. Another important difference is that, when fully implemented in 2010, the federal fleet average NMOG emissions—around 0.090 g/mi, based on Bin 5—can be more than twice as high the LEV II NMOG levels.

Table 5 shows the percentage breakdown of vehicles certified to the various emission categories—based on NMOG certification—in model year 2008. As apparent from the data, average new vehicles in 2008 were approximately regulated at ULEV NMOG levels.

Table 5
California MY 2008 Emission Certification Levels for NMOG
CategoryLEVULEVSULEV*Sales Volume
* Includes PZEV, which accounted for 92% of the SULEV+PZEV category

Low Emission Vehicle III (LEV III) Standards

The LEV III emission standards—adopted in January 2012 and amended in December 2012 [2946]—are phased-in over the 2015-2025 model years. Manufacturers can certify vehicles to the LEV III standards before model year 2015. Beginning with model year 2020, all vehicles must be certified to LEV III standards.

The LEV III standards modify the LEV II standards in several ways: (1) combine NMOG and NOx standards into one NMOG+NOx standard, (2) introduce a more stringent combined NMOG+NOx fleet average requirement for 2015-2025 model years, (3) add several emission standard bins, and (4) increase the durability requirements for emission control systems.

LEV III emission categories and their FTP-75 standards for light- and (chassis-certified) medium-duty vehicles are listed in Table 6. The numeric portion of the category name is the corresponding NMOG+NOx value in mg/mi.

Table 6
LEV III Emission Standards, Durability 150,000 miles, FTP-75
Vehicle TypeEmission CategoryNMOG+NOxCOHCHOPM†
All PCs
LDTs ≤ 8500 lbs GVWa
MDVs 8501 - 10,000 lbs GVWb LEV3950.3956.460.12
MDVs 10,001 - 14,000 lbs GVWb LEV6300.6307.360.12
† - Applicable only to vehicles not included in the phase-in of the final PM standards (Table 7 & Table 8).
a - Loaded vehicle weight (LVW)
b - Adjusted loaded vehicle weight (ALVW)

  PC - Passenger car
  LDT - light-duty truck
  MDPV - medium-duty passenger vehicle
  MDV - medium-duty vehicle

SFTP and other testing requirements and standards, not shown in the table, are also applicable (for instance, HWFET and Cold CO standards).

Particulate Matter Standards. The PM emission standards shown in Table 6 will be tightened to much more stringent levels listed in Table 7. The phase-in schedule for LEV III PM standards is shown in Table 8 (the numbers denote the percentage of manufacturer’s vehicle fleet that must be certified to a given standard).

Table 7
LEV III Particulate Matter Emission Standards, FTP-75
Vehicle TypePM LimitPhase-in
PCs, LDTs, MDPVs32017-2021
MDVs 8501-10,000 lbs82017-2021
MDVs 10,001-14,000 lbs102017-2021
Table 8
Phase-In Schedule for LEV III PM Standards, % of vehicles
PM = 3 mg/miPM = 1 mg/miPM = 8/10 mg/mi

The SFTP limits for PM are 10 mg/mi for all PCs and for LDT1s (0-3750 lbs LVW), and 20 mg/mi for LDT2s (3751-8500 lbs LVW).

The more stringent standards have been adopted to ensure there is no increase in PM emissions from future engine technologies and that particulate filters are used on all diesel engines. In gasoline direct-injection engines, the future PM standards may trigger the use of gasoline particulate filters.

The LEV III proposal also included a particulate emission compliance option using a solid particle number (SPN) limit that was withdrawn from the final regulation. The proposed limit was 3 × 1012 1/mi. SPN emissions were to be measured over the FTP-75 cycle using a sampling approach patterned after the European PMP method.

Fleet Emission Requirements. New, stringent fleet emission requirements are phased-in, with the light-duty vehicle fleet reaching a SULEV-equivalent fleet average NMOG+NOx emission level of 0.030 g/mi in model year 2025 (Figure 1). Based on the emission certification and sales volume figures from Table 5, the average NMOG+NOx emissions in 2008 were 0.112 g/mi. Therefore, the LEV III fleet average requirements will result in a 73% reduction of NMOG+NOx emissions by 2025.

Figure 1. LEV III Fleet Average NMOG+NOx Standards

LDT1: 0-3750 lbs LVW. LDT2: 3751-8500 lbs LVW.

Medium-duty vehicles have no fleet average requirements. Rather, a phase-in schedule requires manufacturers to certify increasing percentages of their MDVs to increasingly more stringent emission categories. For diesel MDV, manufacturers can also choose to certify the engines to the applicable heavy-duty diesel engine emission standards.

Durability. The LEV III standards phase-in a new 150,000 miles durability requirement, compared to the LEV II 50,000 and 120,000 miles standards. Manufacturers receive a 5 mg/mi FTP NMOG credit for extended, 150,000 mile warranty coverage.

Evaporative Emissions. All light-duty vehicles would have to meet a more stringent “zero” evaporative standard, while using more challenging test fuels, such as E10.

Direct Ozone Reduction Credit. Manufacturers receive an NMOG credit for direct ozone reduction systems (such as ozone reducing catalysts coated on vehicle radiators). The in-use performance of the system must be monitored via an OBD strategy.