ITDP × UC Davis Institute of Transportation Studies · Compact Cities Electrified series
Compact Cities Electrified: The Benefits of Small Vehicles
Five scenarios for urban passenger transport to 2050 across six countries — and the first country-level outlook to model vehicle size as a policy variable rather than a fixed fact. Holding cars at 2020 sizes cuts household transport costs 19–22% on its own.
- Date
- Mar 2026
- Role
- Co-author & lead analyst
- Methods
- Scenario modeling, Urban fleet modeling, Multi-impact assessment
- Tools
- Python, Excel/VBA
1.2Gt CO₂e
Annual GHG reduction
Six countries combined, Shift+EV+Small vs BAU, 2050
19–22%
Cost saving from size alone
Private direct costs, smaller vehicles vs continued growth
1.5M/yr
Premature deaths avoided
Active-mobility health benefit in 2050
6 × 5
Scope
Countries × scenarios, modeled to 2050
Overview
Two of the three things that decide what urban transport costs a country are modeled everywhere: how people travel, and what powers the vehicles. The third — how big the vehicles are — is normally treated as a given. It is not a given. SUVs went from about a fifth of global light-duty sales in 2010 to half by 2022, and every country in this study is on that curve.
This report is, to the authors' knowledge, the first country-level transport outlook to model vehicle size explicitly as a scenario variable and price it across the full set of impacts. It runs five scenarios to 2050 for Brazil, China, India, Indonesia, Mexico and the United States, and reports what each one does to energy use, greenhouse gas emissions, direct public and private costs, battery requirements, road safety, air pollutants and physical health.
The finding is that size is worth pulling — smaller vehicles alone cut private transport costs 19–22% and battery requirements 12–14% — but that no single lever is sufficient on its own. Only the combined Shift+EV+Small pathway cuts annual emissions across the six countries by more than two thirds, and it gets there needing 4% more battery capacity than business as usual rather than several times more.
The question
Transport outlooks model two levers and assume the third. Mode shift and electrification get scenarios; vehicle size gets whatever trend line the fleet is already on. That assumption is doing a lot of work, because the trend is steep — nearly all of the past decade's growth has been in smaller SUVs, but average size has risen throughout, and the large-SUV share that has already reshaped the United States is available to every other market.
So the question here is what that drift costs, and what reversing it is worth, measured in the same units as the levers policy already argues about: energy, emissions, batteries, money, road deaths, air quality and public health. It has to be asked alongside the other two rather than in isolation, because the levers interact — a smaller car needs a smaller battery, and a trip not taken by car needs no battery at all.
Scenarios
The five scenarios reported. Modal split and electrification are carried over unchanged from the 2023–24 Compact Cities Electrified country reports, so vehicle size is the only new variable. All eight permutations were modeled; five are reported, to keep the comparison legible.
| Scenario | Modal split | Electrification | Vehicle size |
|---|---|---|---|
| Business as Usual | Car-oriented | Slow | Continued growth |
| Small Vehicles (Only) | Car-oriented | Slow | Held at 2020 sizes |
| High EV (Only) | Car-oriented | Fast | Continued growth |
| Mode Shift (Only) | Transit, walk, cycle | Slow | Continued growth |
| Shift+EV+Small | Transit, walk, cycle | Fast | Held at 2020 sizes |
Source: ITDP & UC Davis (2026), Figure 3.1.a.
Figure 1
Effect of the vehicle-size lever alone, by impact category, 2050
Reduction delivered by holding new-vehicle sizes at 2020 levels, measured against the same scenario with sizes continuing to grow. Each bar spans the range across the six countries. The lever is worth most where size policy is least often argued — what households spend on getting around — and least on the headline emissions number that transport policy usually leads with.
Range chart of the reduction delivered by smaller vehicles alone across six impact categories in 2050, as a percentage. Private direct costs 19 to 22 percent, the largest effect. Battery requirements 12 to 14 percent. Liquid fuel requirements 11 to 14 percent. Electricity consumption 8 to 12 percent. Traffic deaths 8 to 9 percent. GHG emissions 4 to 10 percent.
Source: ITDP & UC Davis (2026), Compact Cities Electrified: The Benefits of Small Vehicles, Executive Summary. Ranges across Brazil, China, India, Indonesia, Mexico and the United States.
Data table
| Impact category | Reduction across the six countries |
|---|---|
| Private direct costs | 19–22% |
| Battery requirements | 12–14% |
| Liquid fuel requirements | 11–14% |
| Electricity consumption | 8–12% |
| Traffic deaths | 8–9% |
| GHG emissions | 4–10% |
Approach
Each country's fleet, travel activity and energy use are projected to 2050 from a 2015 base year, built on the International Energy Agency's Mobility Model and modified with country-specific data, with 2025 estimates reported alongside. The modal-split and electrification scenario definitions are the ones already published in the 2023–24 country reports, used unchanged, so that the new variable is the only thing moving.
The size scenarios were built from scratch, on vehicle-registration data assembled by UC Davis and ETERC for the Global Fuel Economy Initiative. Business as Usual continues the observed drift toward larger vehicles. Small Vehicles returns the new-vehicle size mix to 2020 levels by 2030 and holds it — a ceiling on growth, not a fleet of microcars. Where cars are already small, it means they stay small.
Assumptions were chosen to understate rather than overstate the gap between scenarios. Autonomous vehicles are excluded, on the grounds that their uptake is too uncertain to model without swamping everything else. The study covers urban passenger transport only — roughly 60–70% of national passenger travel — so freight, intercity and rural travel sit outside it, and the results are a floor on the full effect rather than a ceiling.
Impacts in 2050
Annual savings in 2050, against Business as Usual, for the combined Shift+EV+Small pathway. The electricity and battery rows are the exception: they are measured against High EV (Only), because the point there is how far electrification's own demands fall once the other two levers are pulled. Figures are the report's rounded estimates.
| Annual saving in 2050 | Mexico | Brazil | China | India | Indonesia | USA |
|---|---|---|---|---|---|---|
| Electricity, PJ | 200 | 200 | 1,000 | 500 | 200 | 600 |
| Liquid fuel, M bbl gasoline-eq. | 100 | 200 | 800 | 500 | 200 | 800 |
| GHG, kt CO₂e | 50,000 | 60,000 | 400,000 | 200,000 | 70,000 | 300,000 |
| Direct public & private cost, $bn | 200 | 200 | 2,000 | 700 | 100 | 900 |
| Battery capacity, GWh | 100 | 100 | 800 | 400 | 50 | 400 |
| Road fatalities avoided | 2,000 | 10,000 | 40,000 | 90,000 | 10,000 | 8,000 |
| PM2.5, kt | 9 | 8 | 60 | 30 | 50 | 40 |
| Premature deaths avoided, active mobility | 50,000 | 80,000 | 700,000 | 300,000 | 100,000 | 300,000 |
Source: ITDP & UC Davis (2026), Figure 5.1.a. Liquid fuel in millions of barrels of gasoline-equivalent, per §5.2.
Key findings
- 01
Vehicle size is worth a fifth of household transport spending
Holding new cars at 2020 sizes cuts private direct costs 19–22% in every country modeled, before anything is electrified or any trip is shifted. It is the largest single-lever effect the study found on what transport costs people.
- 02
Smaller cars are how electrification gets paid for
Size and mode shift both cut the battery capacity a country needs. Together they deliver High EV outcomes on only 4% more battery capacity than business as usual — the difference between a supply chain that exists and one that has to be built.
- 03
Electrification does nothing for the road toll
High EV leaves road deaths, non-tailpipe particulates and low-income travel costs roughly where BAU leaves them. Those are mode-shift and vehicle-size problems, and no amount of electrification reaches them.
- 04
Only the combination reaches the climate target
Shift+EV+Small cuts annual urban passenger emissions across the six countries by more than two thirds — about 1.2 Gt CO₂e in 2050 — bringing the sector near the threshold consistent with the Paris Agreement. No single lever gets there.
- 05
The largest health effect is not the one usually counted
Active travel avoids around 1.5 million premature deaths a year by 2050, roughly ten times the 160,000 road fatalities avoided. Transport health accounting that stops at crashes and tailpipes misses the bigger term.
Implications
For a transport ministry, the result moves vehicle size out of the category of consumer preference and into the category of policy instrument with a price attached. Size responds to the same tools efficiency already responds to — standards, weight- or footprint-based taxation, purchase incentives keyed to size rather than only to drivetrain — and none of them wait on new technology or new infrastructure.
It also changes the sequencing argument. Electrification programmes are usually costed as though fleet composition were fixed. It is not, and pulling the size and mode levers first makes the electrification target cheaper to hit, because a smaller fleet of smaller cars draws fewer gigawatt-hours from the same battery supply. Size policy is not a competitor to EV policy; it is part of how the EV target becomes affordable.
What the study could not quantify points the same way. Road space, parking demand, congestion, street noise and the land they all consume are left out of the totals, which means the estimates here are conservative — the case for reform is at least this strong, and probably stronger.
Published March 2026 by the Institute for Transportation and Development Policy and the UC Davis Institute of Transportation Studies, with support from the FIA Foundation. Reich, D. T., Fulton, L., Jamhar, J., Blanco, M., Ribeiro, L., Liberman, M., Wiegers, A. & Mason, J. (2026). Compact Cities Electrified: The Benefits of Small Vehicles. Results for the scenario permutations not reported in the publication are available from ITDP on request.