Publications·April 28, 2023
In 2023, Clean Air Asia, School of Environment at Tsinghua University, and the National Big Data Alliance of New Energy Vehicles jointly released this research report reviewing how Chinese trucks progressed in 2022 in terms of cutting their carbon and criteria pollutant emissions. The study was supported by Energy Foundation China and compiled by Clean Air Asia.
Based on multiple sources of data, the report focuses on the emissions of trucks, taking a third-party perspective to assess the progress and effectiveness of criteria pollutant and carbon emission reduction in the truck industry . It also identifies weak links in the green transformation of the industry and provides recommendations for its stakeholders.
Produced by Clean Air Asia (CAA) with academic and data partners (including Tsinghua University and the National Big Data Alliance of New Energy Vehicles), this industry study tracks how China’s truck sector is cutting air pollutants (NOx, PM) and CO₂, and what must accelerate to reach deep pollution control and decarbonization. Trucks are only ~11% of China’s vehicle stock yet account for >50% of vehicle CO₂, >80% of NOx, and >90% of PM—so progress here is pivotal for both public health and climate. The report blends multi-source evidence (annual inspection data, remote OBD, PEMS, “follow-vehicle” testing, sales/stock datasets, and real-world NEV telematics) to evaluate policy and technology performance, then offers a roadmap for 2025–2035.
What’s working now
1) Tightening standards + in-use oversight are cutting diesel emissions.
China’s move to China 6 diesel standards, ultra-low-sulfur diesel (<10 ppm), and stronger urea (SCR) compliance delivers measurable drops in in-use pollution. From China 4 → China 5, average smoke opacity and NOx concentrations in annual inspection fell 21.1% and 24.7%; China 5 → China 6 brought a further 33.3% and 55.5% decline. Even for China 5 trucks, average NOx detected in 2021 was 11.5% lower than 2020 (and 15.8% lower than 2019), showing the regulatory squeeze works beyond new sales.
2) A stronger in-use limit would unlock the next tranche of reductions.
Current annual inspection limit “a” identifies too few high emitters. Modeling shows a stricter limit “b” would capture 18.5–34.0% of China 5/4 high-NOx trucks for repair or retirement. If all China 4 exceedances were replaced with China 6 or BEV trucks, 2021 NOx from diesel freight could fall ~5.3–9.7%—helping hit the 2025 targets (e.g., −12% total NOx, ≥40% share of China-6 + NEV in truck fleets).
3) NEV trucks are scaling quickly—and maturing operationally.
NEV truck sales hit 172,000 in 2022 (≈4.6× vs end-13th FYP), pure battery and fuel-cell models accounting for 99.2% (≈168k BEV, 3,074 FCEV). The coverage of cities selling BEV trucks expanded from 254 → 329 (2019→2022), with diffusion from Tier-1 to Tier-2/3 and lower-tier markets. Heavy-duty battery-swap solutions “broke through,” taking 57.6% of BEV HD tractor sales in 2022; FCEV heavy trucks rose from <20 (2020) to ~2,000 (2022). Utilization is improving (higher online rates, greater daily hours), and fast-charge predominates in most segments; FCEVs retain a refueling-time advantage (typical stop ~25.8 min vs fast-charged HD BEV ~42 min).
4) Some diesel fuel-economy leaders already beat the draft Phase-4 limits.
After Phase-3 fuel-use limits took effect, declared fuel consumption for key segments fell 4–11.4%. Notably, 7.1% of popular 3.5–4.5 t cargo trucks are ~10% below the draft Phase-4 limit (and the best are ~25% below), implying the next standard could raise ambition without breaking feasibility.
Where the gaps are
Natural-gas heavy trucks’ NOx is under-controlled in real-world use.
Lean-burn China 5 CNG/LNG heavy trucks can emit NOx >2× comparable China-5 diesel levels on-road; China 6 gas trucks improve (stoichiometric + TWC), but tampering (e.g., catalyst removal) causes severe exceedance. Today, >70% of gas HDs are still tested via double-idle methods (poor for NOx), and remote OBD policies don’t yet require NOx sensors + data upload for gas HDs. Conclusion: gas fleets need fit-for-purpose methods (e.g., work-cycle tests, remote sensing, follow-vehicle, PEMS, and OBD with NOx sensors) to manage NOx properly.
Heavy-duty BEV still short on long-haul suitability—yet improving.
In 2021, typical BEV HD trucks averaged <150 km/day, vs ≥250 km/day for highway freight. That reinforces BEV’s current niche in short-haul, fixed-route, yard/port shuttles; battery-swap corridors and high-power charging can extend reach, but infrastructure density and turn-time still gate mainstream long-haul substitution.
WTW climate benefit depends on the grid.
For 3.5–4.5 t BEV cargo trucks, well-to-wheels CO₂ reductions vs China-6 diesel vary from ~72.1% (south-west hydropower-heavy grids) to ~8.6% (coal-heavy northern grids). Decarbonizing electricity and introducing low-carbon fuel standards magnifies transport’s WTW gains.
Performance is uneven across OEMs.
For HD tractors, the lowest-emitting brand’s average in-test NOx is ~58% below the worst; in light dump diesel, best-in-class fuel use is ~16.5% below segment average; in light BEV cargo (1.8–3.5 t), energy use varies by ~72% across brands. The “Green Truck List” ranks OEMs and models to pull the market toward top performers.
What the report recommends (actionable takeaways)
1) Raise in-use limits and fuse data sources for enforcement.
Adopt limit “b” nationwide (phased and regionalized), pair it with closed-loop enforcement and expanded roadside/doorstep checks, and integrate annual inspection, remote OBD, PEMS, remote sensing, and follow-vehicle data—supported by calibration/traceability and measurement certification—to target high emitters, retire China-4, and incentivize China-6/NEV uptake.
2) Fix gas-truck NOx.
Stand up fit-for-purpose test methods and limits for in-use CNG/LNG HD trucks; require NOx sensors and real-time uploads for China-6 gas HD; use “Sky-Road-Vehicle-Human” (satellite/remote sensing + roadside + OBD + field checks) to curb tampering. Provinces with high gas-HD shares (e.g., Shanxi, Ningxia, Xinjiang, Inner Mongolia, Shaanxi) should issue targeted plans.
3) Lead with stronger standards—pollutants and GHG together.
Prepare China 7 on an aggressive timetable (multi-pollutant, full-cycle control) and tighten Phase-4 fuel-use limits to reflect best available efficiency. Consider GHG limits for ICE trucks (as US/EU are doing), and strengthen real-driving metrics to close the lab-road gap.
4) Scale NEV trucks with smart constraints + incentives.
Create credit/mandate frameworks for commercial vehicles; set clean-fleet quotas for large shippers; deploy green logistics zones; offer toll relief/road-access for zero-emission trucks. Build charging, battery-swap, and hydrogen networks where freight demand justifies it; pilot green freight corridors on major trunk routes. Keep investing in battery energy density, thermal safety, charging speeds, and hydrogen cost reductions to widen feasible use-cases.
5) Coordinate with the energy transition (WTW thinking).
Maximize renewable share on-grid, push low-carbon fuels standards, and evaluate options by technical fit, economics, and WTW impact per segment (urban light-duty, regional middle-duty, heavy long-haul).
6) Share responsibility across the value chain.
Regulators must set/verify rules; OEMs must field ultra-low/near-zero tech and transparent data; fleets should prioritize NEV where feasible, otherwise China-6 best-in-class; and corridor operators should partner on infrastructure and operations to sustain utilization.
Why it matters now
China’s truck sector is moving—China-6, tougher in-use oversight, sharp NEV growth, and nascent battery-swap/FCEV corridors. But to meet air-quality and “dual-carbon” goals, the report shows a need to tighten, target, and scale: tighten in-use and design standards; target persistent outliers (gas HD NOx, tampering); and scale NEVs and infrastructure along the freight network—while greening the grid so WTW benefits fully materialize.
Keywords
Trucks; NOx/PM; China-6 → China-7; PEMS, remote OBD, remote sensing, follow-vehicle testing; NEV trucks (BEV/FCEV); battery-swap; fast charging; in-use limits; fuel-economy Phase-4; WTW CO₂; green freight corridors; OEM benchmarking.