Studies · CA Air Quality · Investigation 02

Which Transport Strategy Saves the Most Lives?

Five electrification scenarios for California’s vehicle fleet: ACC II baseline, accelerated, delayed, equity-weighted, and heavy-duty-first. The optimal pick depends on fleet turnover speed and on how much of the PM2.5 gain the NOx-ozone chemistry gives back.

T2 Optimal
40.5% Probability
1,314
Deaths Avoided (2035)
$2B
T2 Cost
$0.229B
EVPI
Five Scenarios

From Baseline to Aggressive Acceleration

Scenario Description Cost Deaths Avoided (2035)
T1 Baseline ACC II trajectory: 35% ZEV new sales 2026, 100% by 2035 $0 950
T2 Accelerated $2B incentives, ACC II targets 3 years early $2B 1,314
T3 Delayed ACC II waiver lost, market-driven only −$0.5B 399
T4 Equity Same total as T1, LA Basin/SJV get 1.5× reduction $1B 1,231
T5 Heavy-Duty LDV same as T1, aggressive HDV NOx reduction $1.5B 985

Deaths avoided are relative to the no-policy baseline (14,665 deaths/yr) at year 2035. All scenarios evaluated across 10,000 MC draws at 5-year intervals from 2025 to 2040.

The Ozone Offset

Every PM2.5 Gain Has an Ozone Cost

Cutting tailpipe emissions cuts PM2.5 directly. It also cuts NOx, which in VOC-limited urban air leads to increased ozone formation. So transport electrification saves lives through PM2.5 and costs some back through ozone — the same policy, pulling in two directions.

For the optimal T2 scenario at 2035: electrification avoids 586 PM2.5 deaths and causes 118 ozone deaths in VOC-limited LA cells, but also avoids about 158 ozone deaths in NOx-limited Central Valley cells — a net O3 benefit of ~40 deaths on top of the PM2.5 gain. Net deaths avoided: 626. The headline 20% ozone offset captures only the LA-side penalty against statewide PM2.5 gains; the full picture is regime-dependent.

T5 (Heavy-Duty First) concentrates harm. HDV NOx is heavily loaded on highway corridors that cut through VOC-limited LA cores. T5 is still net positive statewide (+95 deaths avoided in 2025, +689 by 2040) because the Central Valley O3 benefit is large, but it pushes 6.4M Californians into net-harm cells in 2025 — 43.4% of the LA Basin population. See Inv 07 for the spatial detail.

Decision Uncertainty

T2 Wins, But Not Decisively

T2 (accelerated) is optimal in 40.5% of Monte Carlo draws. T4 (equity) is nearly tied at 39.2%, and T1 (baseline) wins in 20.2%. No other scenario is ever optimal. The EVPI of $0.229B is the largest of any single-sector investigation — meaning this is where uncertainty matters most for the decision.

T4 concentrates reductions in the LA Basin and SJV, where population density and baselines are highest, avoiding 1,231 deaths for $1B — nearly matching T2’s 1,314 at half the cost. The three-way race between T1, T2, and T4 is what drives the high EVPI; resolving the CRF would break the tie.

Finding
Accelerated transport electrification (T2) is the optimal strategy with 40.5% probability, avoiding 1,314 deaths by 2035 at $2B cost — but equity-weighted T4 avoids 1,231 at half the cost. Every scenario loses ~20% of its PM2.5 benefit to local ozone disbenefits. Heavy-duty-first (T5) is net positive statewide but concentrates harm on 6.4M Californians. The $0.229B EVPI signals this is the decision most sensitive to CRF uncertainty.

10,000 Monte Carlo draws · 5 scenarios × 4 time horizons (2025–2040) · ISRM source-receptor for PM2.5 · InMAP 2-level for NOx · Ozone disbenefit via NOx-VOC titration model · VOI at 2035 horizon · EPA BenMAP CRFs · ACC II scenario definitions from CARB

← Previous Baseline Health Burden Next → Building Electrification