VEHICLE GREENHOUSE GAS EMISSIONS STANDARDS FOR HEAVY-DUTY VEHICLES — PHASE 3 AND THE UNCERTAINTY AHEAD

Volume-07 Issue 12, December-2023 ISSN: 2456-9348 Impact Factor: 6.736 International Journal of Engineering Technology Research Management (IJETRM) https://ijetrm.com/ IJETRM (http://ijetrm.com/) [624] VEHICLE GREENHOUSE GAS EMISSIONS STANDARDS FOR HEAVY-DUTY VEHICLES — PHASE 3 AND THE UNCERTAINTY AHEAD Muhammad Waleed Saleem, Muhammad Haris Saleem, Muhammad Adeel Sajjad Independent Researcher ABSTRACT The U.S. Environmental Protection Agency (EPA) has proposed new Phase 3 greenhouse gas (GHG) standards for heavy-duty vehicles (HDVs) beginning in model year (MY) 2027, following the existing Phase 1 and Phase 2 programs. The proposal outlines more stringent CO₂ emission targets intended to accelerate fleet decarbonization while preserving manufacturer flexibility. However, the Phase 3 rule is subject to deep uncertainty across multiple dimensions: technology realization, infrastructure readiness, market adoption of zero-emission vehicles (ZEVs), and legal/regulatory durability. This paper (i) synthesizes the status of the Phase 3 proposal, (ii) identifies the principal uncertainty domains, and (iii) develops a three-scenario framework with illustrative quantitative bounds to guide fleet planners, regulators, and researchers. Scenario-based estimates suggest that, plausible median reductions of 15 − 25 % in well-to-wheel 𝐶𝑂₂𝑒 intensity by 2032 are feasible under an optimistic adoption path, but downside cases (e.g. delayed ZEV deployment or rollback risk) could compress reductions to <10 %. The paper argues for embedding uncertainty disclosure, regulatory durability safeguards, and staged transition flexibility into any final rule. 1. INTRODUCTION Heavy-duty trucks and buses (Classes 2b to 8) represent a critical piece of the U.S. decarbonization challenge: though relatively few in number, they consume large volumes of diesel fuel and thus produce disproportionate greenhouse gas (GHG) emissions in the freight and transit sectors. The existing Phase 1 (MY 2014–2018) and Phase 2 (MY 2018– 2027) EPA/NHTSA programs have mandated incremental improvements in fuel efficiency and CO₂ emissions for HDVs and engines. In April 2023, EPA published a proposed rule for Phase 3 GHG standards, targeting MY 2027 onward, and solicited comments through mid-2023.[1] At this stage, key design decisions are public, but much remains unsettled, particularly on crediting, ZEV trajectories, and compliance flexibilities. The time horizon to MY 2027–2032 magnifies uncertainties in technology, infrastructure, and legal risk. Given the long life and capital intensity of heavy trucks, decisions made now will influence compliance pathways and fleet strategies for years to come. This paper aims to (a) clarify the current structure of the proposed Phase 3 rule, (b) categorize the major uncertainty domains that will affect realized outcomes, and (c) propose a scenario + bound methodology that fleets, OEMs, and regulators can use to stress-test outcomes. Although detailed numerical simulation requires proprietary fleet data, the framework herein is designed to be implementable using open sources (e.g. EPA’s HD TRUCS tool, industry data, LCAs) and to encourage transparent uncertainty reporting in the final rulemaking. 2. STATUS OF THE PHASE 3 PROPOSAL 2.1 Overview of proposal and timing On April 27, 2023, EPA published the Proposed Rule: Greenhouse Gas Emissions Standards for Heavy-Duty Vehicles — Phase 3 (Docket EPA-HQ-OAR-2022-0985) covering vocational trucks and tractors beginning MY 2027.[1] The proposal includes a draft Regulatory Impact Analysis (RIA) and solicits stakeholder comment on technology feasibility, cost assumptions, and credit flexibilities. Per the proposal, targets are set relative to the Phase 2 MY 2027 baseline, with steeper annual tightening through MY 2032. The rule would maintain a technology-neutral, performance-based approach, similar to earlier phases, allowing OEMs to mix internal combustion engine (ICE) improvements, hybrids, or ZEV deployment to comply.[2] Volume-07 Issue 12, December-2023 ISSN: 2456-9348 Impact Factor: 6.736 International Journal of Engineering Technology Research Management (IJETRM) https://ijetrm.com/ IJETRM (http://ijetrm.com/) [625] Some public sources note that the finalization timetable may aim soon for the final rule, though commentators caution delays are likely given legal and stakeholder complexity. Because of those risks, many fleets and OEMs are already scenario-stress testing their investment paths. 2.2 Key structural elements and constraints • Baseline and glide path: The proposal uses Phase 2 MY 2027 levels as the starting point. The glide path tightens CO₂ per unit distance or ton-mile metrics in vocational and tractor classes.[1][2] • ZEV adoption ceilings and interpolation: EPA’s draft modeling imposes maximum ZEV penetration caps (e.g. 20 % in MY 2027, ramping to perhaps 70 % in 2032 in some segments) with linear or piecewise interpolation.[3] • Credit, banking, and flexibilities: The proposal retains averaging, banking, trading (ABT) mechanisms, off-cycle credits, and provisions for advanced technology credits (e.g. for early ZEV deployment), with stakeholder comment solicited on their parameters.[1][2] • Subcategory differentiation: The rule delineates multiple tractor subcategories (cab style, roof height) and vocational subcategories layered by duty cycle. Each has specific CO₂ (or g/ton-mile) targets.[3] • Feasibility constraints: EPA’s RIA references the HD TRUCS (Heavy-Duty Technology Resource Use Case Scenario) tool to vet technology readiness, cost payback, and adoption curves in key vehicle classes.[4] • Public comments & debates: Stakeholders (OEMs, fleet operators, utilities) have raised concerns around infrastructure lead times, battery cost trends, grid capacity, utility interconnection, duty-cycle degradation, and warranty/maintenance risk. The docket indicates that EPA will consider performance credit limits, ZEV ramp controls, and compliance flexibility in response.[1][2][5] In short, the Phase 3 architecture is well articulated in proposal form, but the final rule’s parameterization will crucially shape real-world decarbonization outcomes. 3. MAJOR SOURCES OF UNCERTAINTY To anticipate how the eventual Phase 3 standard will play out across fleets and emissions trajectories, four major classes of uncertainty should be explicitly considered in analysis and planning. 3.1 Technology Realization Risk Even if the proposed targets are technically within reach on paper, variation in real-world duty cycles, auxiliary load penalties, aging, degradation, and mismatch between test and operational conditions can erode gains. ZEVs introduce additional uncertainties: battery durability, pack cost declines, energy density progression, cold-weather performance, and vehicle total cost of ownership (TCO) reliability in heavy-duty duty cycles. The RIA’s modeling assumptions for ICE improvements or hybrid integration may underestimate negative interactions (e.g., weight penalties, packaging constraints). Thus, actual fleet-level gap to target may be larger than the proposal’s “central case” suggests. 3.2 Infrastructure, Market, and Adoption Risk ZEV adoption is constrained by infrastructure readiness (charging/hydrogen station deployment, grid capacity, utility interconnect timelines, demand charges). Delays or cost overruns in infrastructure could slow vehicle uptake, pushing the fleet mix toward ICE-dominant compliance paths and reducing aggregate GHG abatement. Also, fleet decision behavior, financing, residual value uncertainty, and leasing dynamics influence adoption curves. Market inertia in vehicle turnover rates further compounds delays. 3.3 Upstream Energy and Life-cycle Risk While Phase 3 regulates tailpipe CO₂ (i.e. tank-to-wheel), actual well-to-wheel (WTW) emissions depend on upstream refining (for diesel or alternative fuels) and electricity system carbon intensity (for BEVs). Regional variation in grid mix or unexpected delays in electricity decarbonization will influence net GHG benefit.[6] If electricity remains carbon-intensive in key regions, the relative benefit of electrification is reduced. Hence, in corporate GHG accounting or climate planning, the uncertainty in upstream emissions is nontrivial and must be included in any abatement estimate. Volume-07 Issue 12, December-2023 ISSN: 2456-9348 Impact Factor: 6.736 International Journal of Engineering Technology Research Management (IJETRM) https://ijetrm.com/ IJETRM (http://ijetrm.com/) [626] 3.4 Policy Durability and Legal Risk Perhaps the most critical—and least quantifiable—uncertainty is whether the final Phase 3 rule will remain stable over its lifetime (2027–2032) in the face of political, judicial, or administrative reversal risks. • Legal challenges: Opponents may challenge the rule on Clean Air Act interpretations, cost justification, unreasonable burdens, or crediting scheme design. • Administrative reversal: A future administration might attempt to revise or roll back portions of Phase 3 via notice-and-comment or via reinterpretation of statutory authority. • Congressional dynamics: Legislative changes or rider provisions could constrain EPA’s authority or require changes to test procedures or crediting. Because heavy-duty trucks are long-lived assets, uncertainty about regulatory durability may induce investment limbo or gradual adoption rather than front-loaded compliance effort. 4. SCENARIO FRAMEWORK AND METHODS Three-scenario framework: • Scenario A (“Base/Moderate”): Phase 3 is adopted largely as proposed, ZEV adoption proceeds moderately per EPA’s central modeling, and technology realization is average. • Scenario B (“High Ambition”): Stronger ZEV uptake (faster infrastructure, cost declines), robust ICE/hybrid performance, and full compliance. • Scenario C (“Conservative/Delayed”): Slower ZEV uptake (infrastructure delays), technology shortfalls, or partial rollback pressures, pushing compliance to rely more on ICE improvements. Each scenario yields a range of 𝐶𝑂₂𝑒 intensity reductions by 2032, in both tailpipe (𝑔𝐶𝑂₂/𝑚𝑖) and WTW (𝑔𝐶𝑂₂𝑒/𝑚𝑖 or per ton-mile) terms. 𝐷𝑖𝑒𝑠𝑒𝑙: 𝐸𝑊𝑇𝑊 ≈ (𝐸𝐹𝑇𝑇𝑊 +𝐸𝐹𝑢𝑝𝑠𝑡𝑟𝑒𝑎𝑚) 𝑚𝑝𝑔 ⁄ 𝐵𝐸𝑉: 𝐸𝑊𝑇𝑊 ≈𝑘𝑊ℎ𝑚𝑖 ⁄ × (𝑔𝑟𝑖𝑑 𝐸𝐹) Monte Carlo (≥ 10,000 𝑑𝑟𝑎𝑤𝑠) samples 𝑚𝑝𝑔 𝑘𝑊ℎ − 𝑚𝑖 ⁄, utilization, upstream factors, ZEV shares, and policy timing to deliver medians and 90% intervals; variance decomposition attributes shares to inputs. 4.1 Assumed Baseline and Inputs • Baseline intensity: Diesel HD tractors in freight duty cycles average ~1,100 − 1,300 𝑔 𝐶𝑂₂𝑒/𝑚𝑖 (tailpipe + upstream adders). • Efficient ICE potential: Incremental gains of 15 −25 % over Phase 2 baseline by 2032 under perfect execution. • ZEV contribution: In central paths, assume ZEVs contribute 15 −40 % of new sales by 2032, weighted by segment, with full-life substitution effect. • Upstream spread: Electricity carbon intensity and diesel refining emissions add ±10 −20 % margin to net WTW benefits. • Durability discount: Under uncertainty, cast a 5 − 15 % margin for regulatory drag, market lag, or rollback slippage. 4.2 Illustrative Reduction Estimates Scenario Mid-Case Tailpipe Reduction (2032 vs 2023) Mid-Case WTW Reduction Lower Bound Reduction Upper Bound Reduction A (Moderate) ~18 % ~15 % ~10 % ~25 % B (High Ambition) ~25 %–30 % ~22 %–28 % ~18 % ~35 % C (Conservative/Delayed) ~8 %–12 % ~6 %–10 % ~2 % ~15 % Volume-07 Issue 12, December-2023 ISSN: 2456-9348 Impact Factor: 6.736 International Journal of Engineering Technology Research Management (IJETRM) https://ijetrm.com/ IJETRM (http://ijetrm.com/) [627] These estimates reflect aggregate fleet outcomes; individual segments (vocational, regional trucks, tractors) may vary significantly. The gap between tailpipe and WTW underscores the importance of upstream assumptions. 4.3 Variance Decomposition (Qualitative) In a Monte Carlo or Sobol’ sensitivity analysis, contributions to realized variance might break down approximately: • Technology realization: ~30–40 % • ZEV adoption & infrastructure constraints: ~25–35 % • Upstream emissions variation: ~10–20 % • Policy drag / durability risk: ~10–20 % This decomposition highlights that no single dimension dominates entirely; portfolios of risk accumulate. 5. IMPLICATIONS AND POLICY PRESCRIPTIONS 5.1 For Fleets, OEMs, and Investors • Adopt no-regret technologies now. Even if ZEV rollout lags, advanced aerodynamics, low-rolling-resistance tires, waste-heat recovery, and hybridization yield fuel savings under any scenario. • Modular strategy hedging. Maintain flexibility among ICE, hybrid, and electrified platforms so that capital investments can pivot based on the realized path. • Early pilot ZEV deployment in favorable segments. Urban, regional, or short-haul use cases with predictable duty cycles and depot access are likely lower-risk paths. • Scenario modeling and flexibility options. Build internal models with Scenario A/B/C bounds and track key leading indicators (battery cost, infrastructure permit lag, credit market design). • Baseline WTW intensity for long-haul diesel tractors: ~1,100 − 1,300 𝑔𝐶𝑂₂𝑒/𝑚𝑖 depending on mpg and upstream adders. Scenario A: ~15 −20% median WTW reduction by 2032 (90% 𝑖𝑛𝑡𝑒𝑟𝑣𝑎𝑙 ≈ −10% 𝑡𝑜 − 25%). Scenario B: ~22–30% median (90% 𝑖𝑛𝑡𝑒𝑟𝑣𝑎𝑙 ≈ −18% 𝑡𝑜 − 35% . Scenario C: ~6–10% median (90% 𝑖𝑛𝑡𝑒𝑟𝑣𝑎𝑙 ≈ 0% 𝑡𝑜 − 15%). Variance shares (qualitative): 30 −40% technology, 25 −35% infrastructure/adoption, 10 −20% upstream, 10 −20% policy durability. Segment outcomes vary widely. 5.2 For EPA and Regulators • Embed uncertainty disclosure. The final rule should require that compliance analyses and fleet-level plans include distributional ranges (e.g. 5th–95th percentiles), not just point estimates. • Provide durability assurances. Mechanisms such as mid-course review periods, statutory safe harbors, or multiyear credit banking strengthen regulatory confidence. • Stage infrastructure signals. Coordinate with DOE, DOT, and states to accelerate charging/fueling infrastructure deployment and minimize boom–bust cycles. • Refine credit flexibilities. Design advanced credit multipliers or transition credits to cushion early adoption risk, without undermining stringency. 5. ILLUSTRATIVE BOUNDS (NON-BINDING, FOR PLANNING) Baseline WTW intensity for long-haul diesel tractors: ~1,100 − 1,300 𝑔𝐶𝑂₂𝑒/𝑚𝑖 depending on mpg and upstream adders. Scenario A: ~15 −20% median WTW reduction by 2032 (90% interval ≈ −10% 𝑡𝑜 − 25%). Scenario B: ~22–30% median (90% interval ≈ −18% to −35%). Scenario C: ~6–10% median (90% interval ≈ 0% to −15%). Variance shares (qualitative): 30–40% technology, 25–35% infrastructure/adoption, 10–20% upstream, 10–20% policy durability. Segment outcomes vary widely. Volume-07 Issue 12, December-2023 ISSN: 2456-9348 Impact Factor: 6.736 International Journal of Engineering Technology Research Management (IJETRM) https://ijetrm.com/ IJETRM (http://ijetrm.com/) [628] Figure 1: Illustrative distributions of 2032 WTW CO₂e reduction relative to a 2023 baseline across three scenarios Figure 1 is Intended for planning use only. 6. IMPLICATIONS Fleets/OEMs — Prioritize no‑regret efficiency; pilot ZEVs in ready segments; hedge with modular portfolios; disclose uncertainty bands. Regulators — Embed uncertainty disclosure and mid-course review; structure credits that reward durable early ZEV deployments; coordinate infrastructure programs. Researchers — Expand duty‑cycle datasets; open Monte Carlo toolchains linked to EPA models; refine regional grid projections for HDV WTW accounting. 7. LIMITATIONS Quantitative envelopes are illustrative and should be refined with fleet-specific inputs and finalized parameters. 8. CONCLUSIONS Phase 3 can deliver double‑digit GHG intensity reductions by 2032 if technology, infrastructure, upstream decarbonization, and policy durability converge. Scenario planning with explicit uncertainty bands and staged investment options is essential. REFERENCES 1) EPA (Apr. 27, 2023). Proposed Rule: Greenhouse Gas Emissions Standards for Heavy‑Duty Vehicles— Phase 3 (Docket EPA‑HQ‑OAR‑2022‑0985), draft RIA, and HD TRUCS documentation. 2) Federal Register (Apr. 27, 2023). Greenhouse Gas Emissions Standards for Heavy‑Duty Vehicles—Phase 3 (Proposed Rule). 3) ICCT (2023). U.S. Phase 3 HDV GHG standards—policy briefs and benefits analyses. 4) EPA/NHTSA (2016). Phase 2 Heavy‑Duty Fuel Efficiency & GHG standards—final rule and RIA. 5) Public comments (mid‑2023) on infrastructure readiness, ZEV adoption caps, and crediting design. 6) Open WTW/LCA reviews (2020–2023) on HDV upstream emissions and grid carbon intensity.