Assessing the Air Quality Benefits
of Freight Fleet Electrification

Research Objectives

  • Diesel-fueled trucks raise important health and environmental concerns, notably because they emit significant amounts of chemical compounds and subsequently impact ambient air quality and public health.
  • While on-road freight (including light, medium, and heavy-duty trucks) movements in the Greater Toronto and Hamilton Area (GTHA) represent 19.8% of the overall daily vehicle kilometers travelled (VKT), they account for 26.4% of GHG (in CO2eq), 65.5% of nitrogen oxides (NOx), and 69.4% of PM5 emissions. Among on-road freight vehicles, heavy-duty trucks bear the largest share of emissions.
  • This study proposes an integrated framework whereby the movement of trucks and other on-road vehicles were simulated at the level of every road segment. Subsequently, emissions of road traffic were estimated at the same spatial resolution, generating a highly spatially resolved emission database for road traffic.
  • A chemical transport model (CTM) was employed to generate air pollution exposure surfaces associated with traffic and all other sources under a base case and three different electrification scenarios (light-duty truck electrification, medium-duty truck electrification, and heavy-duty truck electrification).
  • Using population data in dissemination areas and concentration response functions specific to Canadian and local conditions, exposures under the different scenarios were used to quantify the burden of on-road traffic in the GTHA and the benefits of electrifying trucks, along various health outcomes with a particular focus on the main pollutants generated by diesel trucks.
  • Health burdens and benefits were finally investigated while capturing the implications for environmental justice. The following Figure captures a summary of the methodology:
Integrated modeling framework
Study Domains

Results - GHG Emissions & Air Quality

The electrification of heavy-duty trucks:

  • Achieves the highest benefits in terms of improvement in air quality (largest reduction in NO2 (14%) and BC (10%) reduction in daily averaged concentrations), especially in areas located close to highways and major roads or with a high density of freight distribution centers (Peel region).
  • Is associated with the highest reduction in daily GHG emissions (10.5% reduction with respect to the base case), followed by light-duty truck electrification (5% reduction) and medium-duty truck electrification (1.4% reduction).

Under medium-duty truck electrification and light-duty truck electrification:

  • NO2 levels are reduced by similar ranges with some differences in the locations where the reductions occur. This might be caused by their different spatial trip patterns where light-duty trucks primarily operate on major arterial roads and local roads whereas medium-duty trucks are concentrated on the highway network as well as major roads.
  • We observe a slight increase in BC concentrations across some areas which might be related to different assumptions considered for non-exhaust emissions in comparison with the heavy-duty electrification scenario.
Spatial distribution of daily averaged NO2 concentrations (μg/m3) for a) base case, b) light-duty truck electrification, c) medium-duty truck electrification, and d) heavy-duty truck electrification scenarios averaged over the 4 seasons with 1-km2 resolution
Spatial distribution of daily averaged BC concentrations (μg/m3) for a) base case, b) light-duty truck electrification, c) medium-duty truck electrification, and d) heavy-duty truck electrification scenarios averaged over the 4 seasons with 1-km2 resolution

Results - Environmental Justice

  • Dissemination Areas (DAs, the smallest geographic areas where socioeconomic data can be obtained) with a high proportion of most disadvantaged households are exposed to higher levels of air pollutants.
  • Across all scenarios, the highest improvements occur for the most disadvantaged quintile with the heavy-duty electrification scenario generating the highest reduction in NO2 (3.75 μg/m3) and BC (0.12 μg/m3) exposure levels.
Spatial distribution of NO2 concentrations (μg/m3) at DA level derived from the base case condition (right) and material deprivation quintiles (left)
Comparison of variations in NO2 levels (μg/m3) estimated at DA-level under the base case, light-duty truck electrification (Electric_LDT), medium-duty truck electrification (Electric_MDT), and heavy-duty truck electrification (Electric_HDT) across material deprivation quintiles
Comparison of variations in BC levels (μg/m3) estimated at DA-level under the base case, light-duty truck electrification (Electric_LDT), medium-duty truck electrification (Electric_MDT), and heavy-duty truck electrification (Electric_HDT) across material deprivation quintiles
  • The traffic health burden was quantified as the result of an air quality model run whereby all traffic emission sources are removed in the GTHA.
  • All the considered cases are related to PM5 chronic exposure except the all-exposure mortality case which considers the contribution of multiple pollutants (NO2 and O3 acute exposure as well as PM2.5 chronic exposure).
  • Considering the all-exposure mortality, the benefits associated with freight electrification would offset around one-third of the burden imposed by traffic.
  • The heavy-duty truck electrification scenario leads to the highest health benefits with a reduction in yearly chronic exposure premature mortality close to 200 cases for the GTHA.
Annual count estimates attributable to changes in air pollutants (all the cases related to PM2.5 chronic exposure except the all-exposure mortality case) under light-duty truck electrification (Electric_LDT), medium-duty truck electrification (Electric_MDT), and heavy-duty truck electrification (Electric_HDT), including the total burden of all traffic (which includes cars, buses, and trucks)

Summary

This study explores the potential co-benefits associated with electrification, one important pathway towards decarbonization of freight. Our study examines freight electrification in terms of improvement in air quality, increase in health benefits, and reduction in air pollution exposure disparities.

Overall, it is evident that reducing diesel exhaust in populated areas to minimize their adverse health effects is necessary given the significant benefits achieved under the heavy-duty electrification scenario.