Japan: Heavy-duty: Fuel Economy


Japan established the world’s first fuel economy program for medium and heavy-duty vehicles in 2005. The 2015 targets reflect a 10.8% reduction in fuel consumption compared to a 2002 baseline.

Standard type
Fuel economy
Current Standard
2015 Fuel Efficiency Targets

Medium and heavy-duty vehicles

Note: Japan also has 2010 and 2015 standards for light commercial vehicles GVW ≤ 2.5 t and 2015 standards for light vehicles with GVW ≤ 3.5 t used to transport cargo. Additional information can be found on the Light-duty fuel economy standards page.


Japan established the world’s first fuel economy program for medium and heavy-duty vehicles in 2005. The program is fully enforceable in 2015. For more information, see the final report on the 2015 standards.

In November 2005, the Japanese government introduced its first fuel economy standards for new heavy-duty diesel vehicles, which were estimated to be responsible for approximately one-quarter of all carbon dioxide emissions from motor vehicles in 2002. Those standards, affecting commercial trucks with a gross vehicle weight (GVW) in excess of 3.5 metric tons and buses with a carrying capacity above 11 persons, were incorporated into Japan’s broad “Top Runner” system for energy efficiency. The standards set fuel economy improvement targets disaggregated by vehicle type, class, and weight using the top fuel economy performing vehicles from 2002 as a baseline. Recognizing the imperative for vehicle manufacturers to give short-term priority to meeting Japan’s 2009 diesel emission standards, as well as the desire to build in time for one to two model redesigns prior enforcing the targets, the government adopted 2015 as the deadline for compliance with fuel economy targets.

The effectiveness of the standards is enhanced by financial incentives—such as progressive taxes levied on the vehicle weight and engine displacement—that promote the purchase of lighter vehicles. Vehicles that exceed the fuel economy standards and emission standards may be also eligible for additional reductions in vehicle tax. A sticker system is in place that allows customers to identify vehicles that exceed standards.

Technical Standards

The fuel economy standards for commercial vehicles, effective from 2015, apply to diesel fueled, type-approved commercial vehicles with GVW > 3.5 t, including trucks and buses designed to carry 11 or more passengers. The standards are also applicable to non-type-approved diesel vehicles that are equipped with CO or other pollutants emission control devices. Fuel economy from heavy vehicles fueled by gasoline, LPG or other alternative fuels is not regulated.

When the targets are fully met, the fleet average fuel economy is estimated at:

  • For trucks: 7.09 km/L (369.6 g CO2/km), a 12.2% improvement over 2002 performance of 6.32 km/L (414.6 g CO2/km),
  • For buses: 6.30 km/L (416.0 g CO2/km), a 12.1% improvement over 2002 performance of 5.62 km/L (466.3 g CO2/km).

The standards for heavy vehicles are summarized in the following tables.

2015 Fuel Efficiency Targets for Heavy-Duty Transit Buses
Category GVW, t FE Target, km/L
1 3.5 < GVW ≤ 8 6.97
2 8 < GVW ≤ 10 6.30
3 10 < GVW ≤ 12 5.77
4 12 < GVW ≤ 14 5.14
5 14 < GVW 4.23
2015 Fuel Efficiency Targets for Heavy-Duty General (Non-Transit) Buses
Category GVW, t FE Target, km/L
1 3.5 < GVW ≤ 6 9.04
2 6 < GVW ≤ 8 6.52
3 8 < GVW ≤ 10 6.37
4 10 < GVW ≤ 12 5.70
5 12 < GVW ≤ 14 5.21
6 14 < GVW ≤ 16 4.06
7 16 < GVW 3.57
2015 Fuel Efficiency Targets for Heavy-Duty Trucks (Excluding Tractors)
Category GVW, t Max Load (L), t FE Target, km/L
1 3.5 < GVW ≤ 7.5 L ≤ 1.5 10.83
2 1.5 < L ≤ 2 10.35
3 2 < L ≤ 3 9.51
4 3 < L 8.12
5 7.5 < GVW ≤ 8 7.24
6 8 < GVW ≤ 10 6.52
7 10 < GVW ≤ 12 6.00
8 12 < GVW ≤ 14 5.69
9 14 < GVW ≤ 16 4.97
10 16 < GVW ≤ 20 4.15
11 20 < GVW 4.04
2015 Fuel Efficiency Targets for Heavy-Duty Tractors
Category GVW, t FE Target, km/L
1 GVW ≤ 20 3.09
2 GVW > 20 2.01

Fuel economy standards for small buses, defined as vehicles designed to carry 11 or more passengers and with GVW up to 3.5 t, are shown in below.

2015 Fuel Efficiency Targets for Small Buses
Category Fuel Type FE Target, km/L
1 Gasoline 8.5
2 Diesel 9.7

The regulation requires that model fuel efficiency (measured in km/L) and the major efficiency technologies incorporated into vehicles be displayed prominently in catalogs starting in April 2006. The standards themselves are subject to future review based upon technological progress toward meeting Japan’s 2009 heavy-duty emission standards and as improved methods to evaluate the impact of lowered rolling resistance and automatic transmissions for heavy-duty vehicles become available, although no formal review date has been set.


A computer simulation procedure has been developed that allows the calculation of fuel efficiency (in km/L) of heavy-duty trucks and buses based on engine dynamometer testing. The engine testing is performed over the urban JE05 test and over an interurban transient test (speed: 80 km/h, load factor: 50%).

Compliance with the heavy-duty standards is measured by aggregating the fuel economies measured under these test cycles based upon weighting factors reflecting assumptions about the mix of operating environments within which vehicles of a given class and gross vehicle weight operate. In general, lighter vehicles and route buses are assumed to operate almost exclusively in urban environments, while larger vehicles receive heavier weights on the interurban test cycle.

Testing mode by Vehicle Class, Type, and Gross Vehicle Weight
Vehicle Type Vehicle Class GVW (tons) % Weighting
Urban Interurban
Truck Tractors up to 20 80% 20%
20+ 90% 10%
Other up to 20 90% 10%
20+ 70% 30%
Bus Route —- 100% 0%
Other up to 14 90% 10%
14+ 65% 35%

The simulation model assigns standard values by fuel efficiency category for driving resistance and chassis size. Efficiency gains from improving transmission efficiency are minimally credited. Rolling and air resistance, and light-weighting are not credited.

Parameter and Setting for Simulation Model
Parameter Setting
  • Full load torque
  • Engine friction torque
  • Idling engine revolution
  • Max output engine revolution
  • Max engine revolution (w/load)
Actual value For each engine type
  • Number of transmission gears
  • Transmission gear ratios
Actual value For each transmission type
  • Final reduction gear ratio
  • Tire dynamic load radius
(Average) actual value For each engine and transmission type
Driving resistance
  • Rolling resistance
  • Air resistance
Standard values By each fuel efficiency category
Chassis size
  • Kerb weight
  • Maximum load
  • Riding capacity
  • Full height
  • Full width
Standard values By each fuel efficiency category

Manufacturers use transmission specifications meant to representative the “average” transmission sold by a given manufacturer in each category. The fuel economy of automatic transmissions (AT) and automated manual transmissions (AMT) are also estimated through a static discount from the fuel consumption of an equivalent manual transmission (e.g. 0.9 for AT). It is not clear how efficiency improvements from hybrid-electric drivetrains due to regenerative braking and idling stop will be incorporated into the test.

Fuel Economy Determination

The Japanese government measures fuel economy under its heavy-duty standards through a combination of engine-only fuel consumption testing and simulation modeling of gear shifting and vehicle resistance loads, as seen below.

Scheme for Fuel Economy Determination

Japan Scheme for Fuel Economy Determination.png

In Step 1, an engine map is created for each engine type relating fuel consumption to engine speed and torque. That map is generated on an engine dynamometer using instantaneous fuel consumption readings at a minimum of 30 points (6 engine speed points x 5 torque points) spanning the range of normal vehicle operating conditions. In Step 2, full vehicle technical specifications (actual values for engines and transmissions, and fuel efficiency category standard values for rolling resistance and vehicle size) are input into a simulation model that determines gear shift points throughout the test cycle. Those shift positions, combined with vehicle speed, are used to calculate engine speed and torque (Step 3). In Step 4, engine revolutions and torque are paired with the previously generated fuel economy map to produce fuel consumption throughout the drive cycle. This, in turn, is then converted to fuel economy (Step 5).


Compliance with the model year 2015 fuel economy targets is to be measured by reference to individual standards disaggregated by vehicle class, gross vehicle weight, and, for lighter trucks, rated cargo load. Each manufacturer will be required to meet the fuel economy target in each bin it sells vehicles based upon a sales-weighted average for that bin, with no opportunities for cross-bin crediting.

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