Impact of Low-Emission Zones on Spatial and Economic Inequalities using a Dynamic Transport Simulator

André de Palma & Lucas Javaudin

THEMA, CY Cergy Paris Université

June 2025, European Transport Congress

Introduction

Context

  • Road transport sector is responsible for 37 % of nitrogen oxides emissions (NOx) in Europe (EEA, 2021)
  • Nitrogen oxide pollution causes around 40,000 premature deaths yearly in Europe (EEA, 2021)
  • Air pollution causes about 7,920 premature deaths yearly in Paris' urban area, Île-de-France (AirParif, 2022)
  • Popular instrument to improve air quality: Low Emission Zones (LEZ)

Low Emission Zones in France

  • Low Emission Zone: area in the city center where the most polluting vehicles cannot travel
  • In Europe, LEZs have been implemented in hundreds of cities as of today
  • In France, 25 cities have implemented LEZs; cities are forced to implement a LEZ when pollution is above a threshold level
  • [May 2025] Draft law in France that would prohibit LEZs across the country: "low-income households are now forced to choose between incurring significant additional costs to puchase a cleaner vehicle or giving up mobility altogether"

Paris' Low Emission Zone

  • Paris and 76 neighbor municipalities
  • 367 km2 area (3 % of Île-de-France)
  • 5 M inhabitants (40 % of Île-de-France)
  • A86 highway enables detours around the LEZ
  • Since January 2025: Vehicles Crit'Air 3 or worst are banned
  • Crit'Air categories are based on fuel type (diesel, petrol, electric, etc.) and age
  • 68 € fine for non-respect

Île-de-France Vehicle Fleet

  • Municipality-level vehicle fleet data (with Crit'Air categories) from the Ministry of Ecology
  • Extrapolation to predict the fleet in 2025
  • In 2025, around 21 % of vehicles in the region would be Crit'Air 3 or worst

Methodology

Introduction

  • We conduct transport simulations to evaluate ex-ante the impact of the LEZ in Paris
  • Scope:
    • Île-de-France
    • Trips for an average working day
    • Five modes : car (driver), car (passenger), public transit, bicycle and walking
    • All trip purposes
Source: Enquête Globale Transport (2010)

METROPOLIS2

  • METROPOLIS2 is an agent-based dynamic mesoscopic transport simulator
  • Simulation of mode, departure time and route choice, based on discrete-choice theory
  • Congestion simulated from bottlenecks with queue propagation (spillback)
  • Computation of pollutant emissions and exposure of population to pollutants with the METRO-TRACE module

LEZ Policy Evaluation

  • Two METROPOLIS2 simulations:
    • Baseline simulation (calibrated): no LEZ
    • LEZ simulation (counterfactual): January 2025 LEZ (Crit'Air 3 and worse)
  • Limits:
    • Short-run analysis: no car-ownership model, no relocation (of activities or homes)
    • Temporal restrictions of the LEZ not considered
    • Exceptions and cheating not considered

Results

Road Congestion Impact

  • Road congestion decreases on the main highways inside the LEZ (Boulevard Périphérique and A1 motorway)
  • Little impact outside the LEZ

Public Transit Flows Impact

  • Public transit mode share increases from 18.9% to 19.9%
  • Larger flows on most legs, mainly in the surroundings of Paris (North, East and South)
  • RER A: +1.2% passengers-kilometers
  • RER B: +2.1% passengers-kilometers
  • Tramway T7: +24.4% passengers-kilometers

Pollutant Emissions

  • Emissions of PM2.5 and NOx generated by road traffic are computed from the EMISENS model with COPERT emission factors
  • Emissions depend on vehicles fuel type and age as well as instantaneous speed (link-level)
  • Emissions decrease more inside the LEZ
Baseline LEZ Variation
PM2.5 emissions 2.83 tons 2.66 tons -6.0 %
NOx emissions 33.32 tons 30.45 tons -8.6 %
CO2 emissions 21 730 tons 20 829 tons -4.1 %

Population Exposure to Pollution

  • Health impact is a function of the increase in mortality due to exposure to pollutants, given the concentration levels
  • Exposure is computed based on the actual location of individuals in time and space
  • Exposure decreases more near Paris (high concentration and high population density)
Baseline LEZ Variation
PM2.5 premature deaths 5.9 5.3 -9.4 %
NOx premature deaths 5.4 4.9 -10.1 %
Health surplus -12.537 M € -11.312 M € -9.8 %

Heterogeneous Impacts

  • Health impact: between 0 et +30 cents per day per individual
  • Travel impact:
    • 93.2 % are not significantly impacted (variation smaller than 1 € daily)
    • 3.5 % "win" more than 1 € daily
    • 3.3 % "lose" more than 1 € daily

Winners and Losers Location

  • "Winners" are spread over the region
  • "Losers" are mainly living along the LEZ
Winners
Losers

Winners and Losers Income

  • Share of "winners" slightly increasing with the municipality average income
  • Share of "losers" uncorrelated with the municipality average income
Winners
Losers

Conclusion

Conclusion

  • Methodology for the evaluation of public policies with a transport simulator
  • Global impact: decrease of car use, vehicle kilometers, congestion and pollution
  • Individual impact:
    • Health impact distributed evenly across the population
    • Travel surplus impact shows great disparities
  • Characteristics of the winners and losers of the policy
  • Limits:
    • No analysis of the income effect at the individual level
    • Short-run analysis: no car-ownership model, no activity-based model, no location choice model
    • Air pollution from public transit omitted

Thank you