A stepwise guide to heavy-duty vehicle efficiency standards

  1. Overview of the regulatory development process
  2. Market segmentation and duty cycles
  3. Assess the benefit of separate engine and trailer standards
  4. Develop testing and certification procedures
  5. Determine performance metrics and baseline efficiency levels
  6. Set performance requirements, deadlines, and flexibility mechanisms
  7. Drafting, revising, and finalizing the regulation

Heavy trucks and buses—”heavy” meaning a gross vehicle weight more than 3,500 kilograms—account for about 40% of the energy consumption of the global on-road vehicle fleet. In and of itself that makes these vehicles a good target for energy efficiency regulation. Fuel consumption/fuel economy standards and greenhouse gas (GHG) emission limits for new heavy-duty vehicles (HDVs) can also complement other approaches to reducing energy use and carbon emissions in the transportation sector.

Compared to light-duty vehicles, devising efficiency regulations for HDVs is a bigger challenge, because the significant variation in vehicle types, sizes, configurations, mission profiles, and duty cycles creates difficulties in designing test procedures and evaluating performance. But it’s not an insurmountable one.

This card stack briefly lays out the core elements in formulating and implementing an efficiency regulation for heavy-duty vehicles.

  • Overview of the regulatory development process

    The flow diagram below depicts a simplified and idealized process for developing an HDV fuel efficiency regulation.

    Core elements in developing a fuel efficiency regulation for heavy-duty vehicles

    In practice, development of a regulation won’t proceed in such a strictly linear fashion. Reiterations and detours are common, and some tasks can be addressed simultaneously. Nevertheless, the steps in the process are discrete, and they stand in a logical relationship to each other—fully completing one depends on first completing another that is logically prior.

  • Market segmentation and duty cycles

    Development of an HDV efficiency regulation depends fundamentally on first analyzing the market for new and used trucks, buses, engines, and trailers, and then creating an initial vehicle segmentation scheme, along with representative baseline vehicle models and duty cycles in each category based on real-world operations and on levels of technology typical of the best-selling vehicle models.

    Data essential to this element of the process:

    • Overall sales totals (focusing on new vehicles), trends over time, and projections
    • Manufacturer market shares by vehicle size and type
    • Domestic manufacturing versus imports
    • Top-selling models by vehicle segment
    • Typical vehicle technology characteristics and technology baseline
    • Key tier 1 suppliers (e.g., engines, transmissions, trailers)

    Key stakeholders at this stage include vehicle market data vendors; vehicle, engine, and component manufacturers; industry associations; the government agency or agencies responsible for tracking vehicle sales and/or registrations.

    HDVs should be segmented in categories that include vehicles with similar technical characteristics and operational patterns. Otherwise the regulation risks unfairly penalizing certain vehicle types based on mission-related features and operating characteristics. For example, regulating tractor-trailers and medium-duty pickup trucks in the same category would create a situation in which one of the vehicle types is vastly disadvantaged, depending on the chosen performance metric.

    In determining the appropriate number of regulatory categories and duty cycles, policymakers should seek a balance between representativeness and complexity. On one hand, there should be a sufficient number of categories to create conditions for equitable competition. On the other hand, creating too many vehicle categories could increase the administrative burden and complexity of the regulation.

    Manufacturer market shares, new truck and bus sales, india

    Typical component of a market analysis conducted as a data input for an HDV efficiency regulation. (Source)


    Rachel Muncrief and Ben Sharpe, Overview of the heavy-duty vehicle market and CO2 emissions in the European Union

    Ben Sharpe, Market analysis of heavy-duty vehicles in India

  • Assess the benefit of separate engine and trailer standards

    The initial market assessment may or may not include a determination of whether separate requirements for engines and semi-trailers are warranted by the dynamics of the specific vehicle market.

    Data needed to make such an assessment:

    • Component sales totals (focusing on new vehicles), trends over time, and projections
    • Component manufacturer market shares by vehicle size and type
    • Domestic manufacturing versus imports
    • Top-selling component models by vehicle segment
    • Typical technology characteristics and technology baseline

    Key stakeholders to consult include vehicle market data vendors, component manufacturers, and industry associations.

    Comparison, certification pathways, US Phase 2 HDV reg

    This table is a qualitative comparison of various regulatory design options for the second phase of fuel efficiency and greenhouse gas standards for HDVs in the U.S. and Canada. Our primary conclusion from this analysis was that the benefits of maintaining separate engine standards outweighed any potential disadvantages.

    Establishing separate, component-specific requirements can have several advantages:

    • Ensuring long-term investment in efficiency technology R&D for specific components. A regulation that mandates improvements in component efficiency creates an atmosphere of certainty in which manufacturers can make investment decisions.
    • Conforming to distinctive features of the HDV market by allowing components such as engines to be certified individually and sold into many different vehicle platforms. For example, a single heavy-duty engine model is often used in a range of vehicle types. A separate engine standard that complements requirements for the full vehicle allows for engine-related benefits to be realized across all those vehicle segments.
    • In the case of engines specifically, efficiency improvements are often less variable across different operating conditions compared to technology areas such as aerodynamics or tire rolling resistance.
    • In the majority of markets around the world, trailers and tractor trucks are built by different manufacturers. In several regions, this can also be the case for engines.

    Potential disadvantages include:

    • The number of regulated entities increases.
    • More time and resources are required to develop and implement regulations.
    • Integrating separate component standards into requirements for full vehicles and the overall regulation introduces complexity.


    Ben Sharpe, Oscar Delgado, and Rachel Muncrief, Comparative assessment of heavy-duty vehicle regulatory design options for U.S. greenhouse gas and efficiency regulation

    Felipe Rodriguez, Trailer CO2 certification in the European Union

  • Develop testing and certification procedures

    Development of the vehicle segmentation framework and set of duty cycles provides a foundation for the regulatory design phase proper, which begins with designing test procedures and a certification methodology.

    Data required at this stage in the regulatory process includes:

    • Inventory of existing testing facilities
    • Analysis of existing test procedures and applicability to HDV fleet
    • Costs to build and operate testing facilities

    Key stakeholders at this stage include:

    • Testing agencies and research institutes
    • Vehicle, engine, and component manufacturers; industry associations
    • International bodies such as the International Organization for Standardization (ISO) and the World Forum for the Harmonization of Vehicle Regulations
    • Governments with existing HDV fuel efficiency regulations in place

    Experience with testing and certification procedures has confirmed numerous best practices that any new regulation in any market can benefit from. These include:

    • Ensure that any efficiency technologies that provide fuel savings can be accounted for their relative benefits.
    • Promote long-term efficiency investments in the engine and transmission, as well as in vehicle-level systems.
    • Create confidence that the efficiency improvements over the regulatory test procedures result in comparable and durable real-world fuel savings and GHG benefits.
    • Encourage cost-effective technology deployment decisions.
    • Minimize the burden test procedures and certification requirements on both government and regulated entities.
    • Ensure that fuel consumption targets can be met without compromising in-use criteria pollutant emission levels.
    • Leverage existing test procedures, including vehicle simulation models.

    table of advantages/disadvantages, various HDV test methods

    Determining how vehicles will be evaluated for fuel efficiency performance is a critical decision in the regulatory development process. (Source)


    Ben Sharpe, Testing methods for heavy-duty vehicle fuel efficiency: Trends and implications for India

  • Determine performance metrics and baseline efficiency levels

    Once full-vehicle testing protocols are in place, along with protocols for any components that will be separately tested and certified, it’s possible to determine baseline fuel efficiency levels for the representative vehicles in each regulatory category.

    Data needed at this stage include:

    • Component and vehicle characteristics (e.g., tire rolling resistance, aerodynamic drag, auxiliary loads)
    • Engine fuel consumption maps
    • Fuel efficiency results over a range of drive-cycle and payload combinations

    Key stakeholders are testing agencies and research institutes; vehicle, engine, and component manufacturers; industry associations; and regulatory agencies in other governments that already have implemented HDV fuel efficiency regulations.

    Best practices for establishing performance metrics and baseline fuel efficiency levels:

    • Fuel consumption standards are measured in either distance-specific units (e.g. liters per kilometer (l/km)) or distance-payload-specific units (e.g. liters per tonne-kilometer (l/t-km)). Similarly, GHG standards apply metrics such as grams of CO2-equivalent per kilometer or per tonne-kilometer (gCO2e/km or gCO2e/t-km).
    • Payload is important to consider when comparing the efficiency of vehicles used to transport freight. For example, consider two trucks with the following characteristics: Truck A at 0.20 L/km, 10 tonne payload, 0.02 L/t-km, and Truck B at 0.30 L/km, 20 tonne payload, 0.015 L/t-km. Truck B consumes 50% more fuel per kilometer, yet it consumes 25% less fuel per tonne-km, accounting for its higher payload.
    • The baseline values do not need to represent accurate fuel efficiency estimates of exact vehicle models. Instead, the baseline values should be representative of typical models that can be found within each vehicle segment.
    • Validate fuel efficiency results by cross-checking against data from chassis dynamometer and Portable Emissions Measurement Systems (PEMS) testing.

    Several regulatory vehicle simulation models have been developed around the world for the simulation-based certification of CO2 emissions and fuel consumption. A comparison of the tools developed in the United States (the Environmental Protection Agency’s Greenhouse Gas Emissions Model, GEM) and the European Union (the European Commission’s Vehicle Energy Consumption Calculation Tool, VECTO) shows that the simulation-based certification of CO2 emissions is highly sensitive to the vehicle input data, but not significantly sensitive to whether GEM or VECTO is used for evaluation. Thus, it is important to define clear procedures to measure and certify components such that the corresponding vehicle simulation results are accurate.


    Oscar Delgado and Hanyan Li, Market analysis and fuel efficiency technology potential of heavy-duty vehicles in China

    Felipe Rodriguez, Fuel consumption simulation of HDVs in the EU: Comparisons and limitations

  • Set performance requirements, deadlines, and flexibility mechanisms

    Once the baseline fuel efficiency levels have been determined for each vehicle category, performance requirements can be established, including deadlines and any flexibilities that manufacturers can use in demonstrating compliance. This is typically the most time-consuming and resource-intensive step in the regulatory development process—and the most critical.

    Data needed to establish performance requirements include:

    • Existing and anticipated fuel-saving technologies across the entire vehicle
    • Cost data for technology capital and operating expenses
    • Fuel-efficiency results over a range of drive cycle and payload combinations

    Key stakeholders are, once again, testing agencies and research institutes; vehicle, engine, and component manufacturers; industry associations; and regulatory agencies in other governments that already have implemented HDV fuel efficiency regulations.

    Best practices for setting performance requirements:

    • Determine stringency of standards on the basis of either a technology assessment or a best-in-class approach.
      • A technology assessment evaluates the impact of incorporating new technology to improve vehicle efficiency. First, the fuel consumption reduction of each additional vehicle technology is evaluated. Then, combinations of technologies (i.e., technology packages) are assessed for their overall potential to reduce vehicle fuel consumption. A technology assessment may also consider the payback of technologies and the net societal benefits of meeting various targets. An evaluation of this kind requires extensive data collection and modeling, but it is highly useful for setting long-term targets that promote the development of new technologies.
      • An alternate approach is to set targets using information on the best-in-class vehicles already available in the fleet. In such an approach, vehicles leading their respective weight/size class or market segment in terms of fuel efficiency are termed “front-runner” or “top-runner” vehicles. This type of approach is especially useful in setting the stringency of near-term standards, since the target is shown to be achievable by actual vehicles that are already in the market. This approach generally leads to more conservative targets that do not encourage development of new technologies.
    • Give manufacturers enough lead time to prepare for near-term targets. More stringent standards should incorporate longer lead times to give manufacturers adequate time to adjust design cycles of new products.
    • Flexibility mechanisms such as averaging, banking, trading, and advanced technology credits can allow policymakers to set more ambitious standards while enhancing the cost-effectiveness of a given target. If coupled with annual targets or reporting requirements, flexibility mechanisms can facilitate the introduction of technologies where they are most cost effective, provide a greater incentive to improve emissions over the full spectrum of vehicles sold, and allow for more rapid progress towards emissions reduction goals. Such flexibilities should be evaluated carefully so as not to erode the program benefits.
    • Fuel efficiency requirements can be applied either on a corporate average basis or a per-vehicle basis (i.e., establishing a pass-fail threshold).
      • Under corporate average compliance, the sales-weighted fuel consumption of each vehicle model sold must be less than the standard established for that manufacturer for a given model year. Vehicle manufacturers can decide the most convenient schedule for improving the fuel consumption of individual vehicle models so long as they meet the corporate average target. Separate corporate average targets may be applied to vehicle segments.
      • Under a per-vehicle compliance scheme or limit-value approach, each vehicle model must meet the fuel consumption standard established for the vehicle segment to which it belongs. Compliance is achieved before sale of a vehicle, and noncompliant vehicles are barred from the market. The limit-value approach ensures a minimum fuel-efficiency level for each model, regardless of its sales. On the other hand, if the target is not sufficiently stringent, a substantial number of vehicle models may already meet the target and thus have no incentive to improve.


    Oscar Delgado and Hanyan Li, Market analysis and fuel efficiency technology potential of heavy-duty vehicles in China

    Oscar Delgado, Felipe Rodíguez, and Rachel Muncrief, Fuel efficiency technology in European heavy-duty vehicles: Baseline and potential for the 2020–2030 timeframe

  • Drafting, revising, and finalizing the regulation

    The culmination of the regulatory development process is, of course, the regulation, which is itself the product of a process that begins with a proposal, proceeds through stakeholder review, and ends with a finalized standard that incorporates stakeholder input and reflects the overall priorities of the government.

    The data inputs to this step in the process are the outcomes of the technical, economic, and environment analyses conducted in the preceding stages, plus stakeholder comments. “Stakeholders” includes all regulated entities (such as vehicle or component manufacturers), nonregulated industry sectors that will be indirectly impacted by the regulation, relevant ministries or government agencies, and the general public.

    Every jurisdiction will have distinctive requirements concerning proposal notification, the time frame in which stakeholders can provide feedback, and the process by which policymakers integrate this feedback into the final regulation. Drafting of the regulatory proposal need not wait until every stage in the process, from analyzing the market to establishing performance standards, has been completed; it can proceed in parallel with that data-gathering and analysis, as long as the data and analysis is continuously integrated into the proposal.

    The institutional factors called out in the flow diagram must also be addressed if the regulatory proposal is to have a practical effect. Regulatory authority and responsibility must be clear, reporting requirements for manufacturers must be defined, and enforcement framework created. Penalties for noncompliance are essential to ensuring that the efficiency and GHG objectives of the regulation are actually met. Financial penalties must be high enough to provide a real incentive to comply with the standard, which in practice means they must be higher than the cost of technology required.

    Sources [ICCT policy updates]

    The documents below summarize the details of proposed and finalized HDV fuel-efficiency regulations in the United States, Canada, China, India, and the European Union.