Electric Cars Slash Urban Road Emissions by Over One-Third, New Lifecycle Study Reveals
Xi’an, China — In a landmark study that could reshape how cities assess the true environmental impact of transportation, researchers at Chang’an University have quantified—for the first time—the full lifecycle energy and carbon footprint of urban road traffic as an integrated system, coupling both infrastructure and vehicles. The findings are striking: switching from traditional gasoline-powered cars to battery electric vehicles (BEVs) can cut the total fossil energy demand and greenhouse gas emissions of a city’s road network by more than 30 percent—without waiting for cleaner electricity or breakthrough battery chemistry.
The study, published this May in Chinese Journal of Automotive Engineering, breaks from conventional approaches that evaluate roads and vehicles in isolation. Instead, the team led by Fu Pei and senior author Chen Yisong modeled a 10-kilometer stretch of urban arterial road in Xi’an over a 15-year lifespan, factoring in not just asphalt, cement, and construction machinery, but also every component of every vehicle that travels it—from steel and aluminum in the chassis to copper in the wiring and lithium in the battery packs. The result is a holistic picture of what it really costs, in energy and emissions, to keep a city’s traffic flowing.
“This isn’t just about tailpipes anymore,” says Chen Yisong, Professor at Chang’an University’s School of Automobile. “Policy decisions based solely on vehicle tailpipe emissions are dangerously incomplete. You might think you’re greening transport, but if you ignore the carbon embedded in road construction or the emissions from battery production, you could be swapping one kind of pollution for another—or worse, creating hidden environmental debt.”
The conventional internal combustion engine vehicle (ICEV) scenario serves as the baseline. For a single 10-km road segment enduring 16,291 vehicles per day—representative of a busy urban corridor—the total lifecycle fossil energy consumption clocks in at a staggering 3.26 billion megajoules (MJ), with greenhouse gas emissions totaling 216 million kilograms of CO₂-equivalent (CO₂-eq). To put that in perspective, that’s the annual emissions of roughly 47,000 average U.S. households.
But here’s where the narrative shifts. When the same road hosts only BEVs—same traffic volume, same infrastructure—the total energy demand drops to 2.20 billion MJ, a 32.5 percent reduction. Even more impressively, carbon emissions plummet to 138 million kg CO₂-eq, a 36.1 percent cut. That’s more than the emissions saved by simply turning off the tailpipes; it’s a system-wide efficiency gain.
What drives such a dramatic improvement? According to the modeling, the answer lies in the operational phase—not manufacturing. While it’s true that producing a BEV today is more energy- and carbon-intensive than building an ICEV—primarily due to battery materials like lithium, cobalt, and nickel, and the energy required for cell formation—the study shows these upfront costs are overwhelmingly offset during the vehicle’s 150,000-kilometer service life.
Under China’s current grid mix, which still relies heavily on coal, BEVs remain decisively cleaner overall. Why? Because internal combustion is inherently inefficient: roughly 65 to 70 percent of the energy in gasoline is lost as waste heat through the engine and exhaust. Electric motors, by contrast, convert over 85 percent of grid energy into motion. Even with a carbon-heavy power supply, plugging in beats burning fuel barrel-to-wheel.
The data bear this out. In the ICEV scenario, the vehicle operation stage accounts for a colossal 64 percent of total lifecycle emissions—almost all from tailpipe CO₂. Swap in BEVs, and that figure collapses to just 32 percent. Yes, upstream emissions from electricity generation rise, and battery production adds ~18 percent to the vehicle’s manufacturing footprint—but the net effect is still a massive win.
Hybrids tell a more nuanced story. Both conventional hybrids (HEVs) and plug-in hybrids (PHEVs) show moderate improvements: HEVs reduce total emissions by ~27 percent, PHEVs by ~24 percent versus ICEVs. The smaller-than-expected gap between HEVs and PHEVs may reflect real-world usage patterns: many PHEV owners, studies suggest, rarely plug in, effectively driving them as heavier, more complex hybrids. Their added battery and electric motor add manufacturing burden without delivering full electric-mile benefits.
Then there’s the outlier: hydrogen fuel cell vehicles (FCVs). In the current technological and energy landscape, FCVs increase total system emissions—by a sobering 25 percent over ICEVs. The culprit? Hydrogen production. Over 95 percent of the world’s hydrogen today is “grey,” made from natural gas via steam methane reforming (SMR), a process that emits nearly 10 kg of CO₂ for every kilogram of H₂ produced. Even with optimistic assumptions about vehicle efficiency and lightweighting, the upstream emissions from hydrogen dwarf any tailpipe advantage.
“The FCV result isn’t a verdict on the technology,” cautions Fu Pei, the study’s lead author and an engineer specializing in hydrogen systems. “It’s a snapshot of today’s hydrogen economy. If you produce H₂ via electrolysis using surplus wind or solar power—‘green hydrogen’—the picture changes completely. But right now, scaling FCVs without concurrent decarbonization of hydrogen supply would backfire environmentally.”
The researchers didn’t stop at comparing vehicle types. They ran extensive sensitivity analyses to test how real-world variables might alter the conclusions—and the results are instructive for urban planners and policymakers.
First, traffic volume. Intuitively, more cars mean more emissions. But the study reveals that how emissions scale depends on the powertrain. When daily traffic fluctuates by ±10 percent, FCV-based systems show the largest proportional swing in emissions (+9.2% / -9.2%), while BEV systems show the smallest (+8.4% / -8.4%). Why? Because BEVs decouple operational emissions from direct fossil fuel combustion. Their emissions profile is steadier, buffered by the grid’s average carbon intensity. ICEVs and FCVs, both reliant on discrete fossil fuel inputs per mile, are more volatile.
Second, FCV technology progression. The team modeled three future scenarios: reduced hydrogen consumption (from 1.1 down to 0.8 kg/100 km) and vehicle lightweighting (up to 35% mass reduction via advanced composites and design). Even with these aggressive improvements—representing a 2035-level FCV—the total lifecycle emissions only drop to parity with ICEVs. To beat BEVs, you’d need both ultra-efficient vehicles and green hydrogen at scale. It’s a high bar.
Finally, and perhaps most relevant for near-term policy, the team modeled fleet mix scenarios. Today’s Chinese urban fleets are still dominated by ICEVs (~90%), with hybrids, plug-ins, and BEVs making up single-digit shares—and FCVs barely registering (<0.1%). But what if cities accelerate adoption? The researchers simulated three plausible transition paths:
- Scenario 1 (Near-term): ICEVs drop to ~78%, BEVs rise to ~7%
- Scenario 2 (Mid-term): ICEVs ~49%, BEVs ~19%
- Scenario 3 (Ambitious): ICEVs ~21%, BEVs ~34%, hybrids and PHEVs growing steadily
The emissions savings are linear and substantial: a 2.9 percent reduction in Scenario 1, climbing to 11.8 percent in Scenario 2, and a striking 20.2 percent in Scenario 3. Every BEV added to the fleet delivers compound benefits—not just zero tailpipe emissions, but reduced wear on roads (lighter regenerative braking), lower demand for petroleum refining, and decreased local air pollutants like NOx and particulate matter.
What’s often overlooked—and what this study powerfully underscores—is the asymmetry between road and vehicle contributions. Of the total 3.26 billion MJ consumed in the ICEV baseline, a full 77 percent comes from the vehicles, only 23 percent from the road itself. Similarly, vehicles account for 89.5 percent of total CO₂-eq. This flips the script on conventional infrastructure-focused green initiatives. Planting trees along highways or using recycled asphalt are commendable, but they’re tinkering at the margins. The real leverage point is the powertrain.
“The road is a stage; the vehicles are the actors,” says Chen. “You can build the most sustainable theater in the world, but if the play is about coal, the show’s still dirty. Our data says the quickest, deepest cuts will come from electrifying the fleet—not from incremental tweaks to pavement recipes.”
That’s not to dismiss road sustainability entirely. The study confirms that road construction is carbon-intensive—especially cement (emitting ~830 kg CO₂ per ton) and asphalt (~634 kg CO₂ per ton for modified grades). The materials acquisition phase for the 10-km road alone contributes nearly 23 million kg CO₂-eq. Recycling and alternative binders (like geopolymer cements or bio-bitumen) remain important. But their impact is dwarfed by operational emissions.
The implications ripple outward. For city governments drafting climate action plans, this research argues for prioritizing EV charging infrastructure, bus electrification, and purchase incentives over purely road-centric projects. For automakers, it validates the strategic pivot to BEVs—even as they hedge with hybrids—as the most credible path to net-zero mobility. And for investors, it highlights the systemic risk in clinging to internal combustion: as lifecycle accounting becomes standard in ESG reporting, ICEV-heavy portfolios may face sudden devaluation.
Critically, the study also exposes a blind spot in current policy metrics. Many cities boast about “low-emission zones” that ban older diesel vehicles—but if those zones simply fill up with newer gasoline cars or inefficient hybrids, the system-level emissions drop is minimal. True decarbonization requires mandating zero-emission vehicles, not just “lower-emission” ones.
Moreover, the research challenges the notion that BEVs are only as clean as the grid. Yes, a coal-heavy grid reduces their advantage—but crucially, it doesn’t erase it. And grids are getting cleaner, everywhere. China added more solar and wind capacity in 2023 than the rest of the world combined. As the grid decarbonizes, BEVs get cleaner automatically, without needing to be replaced. ICEVs and FCVs running on grey hydrogen, by contrast, are locked into their emission profiles for their entire lifespan.
There’s also the matter of co-benefits the model doesn’t capture: quieter streets, reduced respiratory illness from tailpipe pollutants, lower maintenance costs (fewer moving parts), and energy security (electricity can be domestically sourced; oil cannot). These are harder to quantify but vital to urban livability.
Of course, challenges remain. Battery raw material sourcing—particularly lithium, cobalt, and nickel—raises legitimate concerns about mining impacts and supply chain ethics. The study acknowledges this: BEVs exhibit higher “acidification potential” and “human toxicity” in their manufacturing phase, largely tied to mining and refining. But the authors argue these are manageable through circular economy strategies: robust battery recycling (recovering >90% of key metals), next-gen chemistries (e.g., lithium iron phosphate—LFP—already dominant in China—cuts cobalt demand to zero), and responsible sourcing standards.
The alternative—sticking with ICEVs—simply swaps one set of problems for another: geopolitical oil dependence, volatile fuel prices, and irreversible climate damage.
Looking ahead, the researchers plan to expand the model. Next steps include incorporating vehicle-to-grid (V2G) integration—where parked BEVs feed power back to the grid during peak demand, effectively turning the fleet into a distributed energy storage network—and modeling the impact of autonomous driving on traffic flow efficiency and energy use.
But for now, the message is clear, data-driven, and urgent: electrification isn’t a futuristic ideal. It’s the most effective tool cities have right now to slash the carbon footprint of their transportation systems. And the sooner the transition accelerates, the deeper the cuts will be.
As urban populations swell—68 percent of humanity will live in cities by 2050, up from 56 percent today—the stakes couldn’t be higher. Congested, polluted, carbon-intensive roads are a legacy system that cities can no longer afford. This study provides the empirical backbone for a different vision: silent, clean, efficient urban arteries, humming not with combustion, but with electrons.
The road to net-zero isn’t paved with good intentions. It’s paved with electrons—and, according to this rigorous lifecycle accounting, that’s exactly how it should be.
Fu Pei, Cai Xu, Liu Junzhe, Lan Libo, Yang Yang, Chen Yisong
School of Automobile, Chang’an University, Xi’an 710064, China; College of Transportation Engineering, Chang’an University, Xi’an 710064, China
Chinese Journal of Automotive Engineering, Vol.13, No.3, May 2023
DOI: 10.3969/j.issn.2095‒1469.2023.03.14