Texas A&M Transportation Institute
This project addressed the challenge of accurately quantifying extended idling in heavy-duty vehicles (HDVs), a significant contributor to on-road nitrogen oxide (NOx) and particulate matter (PM2.5) emissions. The U.S. EPA's MOVES model currently uses national averages for idling activity, which fail to reflect local patterns and operational realities. To bridge this gap, the study integrated rich, high-resolution GPS and ELD telematics data from EROAD with other probe datasets and TxDOT in-house sources.
Approach
The work began with a comprehensive literature review, covering two decades of idling research, identifying both methodological advances and persistent gaps in real-world data capture. A multi-stage methodology was then developed:
- Map and quantify heavy vehicle parking capacity – Compiled and validated public and private parking facility inventories, including amenities, county locations, and idling restrictions, verified through GIS analysis and direct contact.
- Determine idling factors – Extracted occupancy and idling patterns from prior studies and scaled them with fresh EROAD data. Bayesian optimisation and machine learning models simulated idling behaviour by facility type, road class, and parking space availability.
- Assess APU availability and use – Cross-referenced manufacturer data and EROAD activity records with the age profile of the Texas long-haul fleet.
EROAD's telematics data proved uniquely valuable due to its mandated HOS compliance tracking, enabling precise identification of idling durations, stop locations, and APU usage. The resulting outputs provide seasonally- and time-of-day-specific idling profiles for all Texas counties, broken down by facility type.
Impact
- Improved Emissions Accuracy – Replaced national-average idling assumptions with location-specific, telematics-derived profiles for the entire state of Texas.
- Regulatory Planning Support – Provided the Texas Department of Transportation with evidence-based idling estimates to support state emissions inventories and compliance planning.
- Replicable Framework – The methodology can be replicated for other states or adapted internationally where similar telematics partnerships exist.
- Targeted Reduction Strategies – Enabled identification of high-idling locations and time periods, supporting targeted interventions to reduce unnecessary idling and associated emissions.