Trends in New York State Vehicle Fleet Composition: Emission Standards and Engine Technology (2015-2024)
FARIHA RIMU, David Q. Rich, Gavin Lemley, Philip K. Hopke, University of Rochester School of Medicine and Dentistry
Abstract Number: 25
Working Group: Urban Aerosols
Abstract
The United States Environmental Protection Agency (EPA) established regulatory frameworks (i.e., Pre-Tier 2, Tier 2, and Tier 3) to address vehicle emissions. Simultaneously, a technological shift from port fuel injection (PFI) to gasoline direct injection (GDI) engines is being adopted. GDI has greater fuel efficiency but potentially produces more secondary organic aerosol (SOA) under Tier 2 emissions than Tier 3. The aim of this study was to examine vehicle fleet transitions in New York State from 2013-2024, specifically the shift between engine technology (PFI and GDI) and fleet turnover rate across emission tiers. We analyzed registration data from the New York State Department of Motor Vehicles and classified vehicles into Pre-Tier 2, Tier 2, and Tier 3 based on Model Year, Vehicle Identification Number (VIN), and regulatory phase-in schedules. We used manufacturer-reported statistics and VIN to categorize vehicles into Pre-Tier 2 PFI, Tier 2 PFI, Tier 2 GDI, Tier 3 PFI, Tier 3 GDI, Hybrid, and EV. All new vehicles sold after 2007 had to meet Tier 2 standards, but only 51% of the total fleet were Tier 2 vehicles in 2013 suggesting a lag time in fleet-wide penetration. Similarly, penetration of Tier 3 vehicles introduced in 2017 was slower than expected and the annual rate dropped in 2019. By 2024 only 34% of the total fleet consisted of Tier 3 vehicles and <5% were EV or Hybrid. Meanwhile, GDI technology adoption by manufacturers increased rapidly for new vehicles and the percentage of GDI vehicles grew consistently from 5% in 2013 to 37% in 2024. The slow fleet turnover highlights a significant lag between regulatory implementation and actual fleet composition changes. This results in continuing emissions, SOA formation and indicates that air quality benefits from Tier 3 will take longer than anticipated to be fully realized.