Preprints
https://doi.org/10.5194/gmd-2021-135
https://doi.org/10.5194/gmd-2021-135

Submitted as: development and technical paper 10 Aug 2021

Submitted as: development and technical paper | 10 Aug 2021

Review status: this preprint is currently under review for the journal GMD.

Comprehensive Automobile Research System (CARS) – a Python-based Automobile Emissions Inventory Model

Bok H. Baek1, Rizzieri Pedruzzi2, Minwoo Park3, Chi-Tsan Wang1, Younha Kim3, Chul-Han Song4, and Jung-Hun Woo3 Bok H. Baek et al.
  • 1Center for Spatial Information Science and Systems – George Mason University, Fairfax, VA, USA
  • 2Department of Sanitary and Environmental Engineering, Federal University of Minas Gerais, Belo Horizonte, Brazil
  • 3Department of Advanced Technology Fusion, Konkuk University, Republic of Korea
  • 4School of Earth and Environmental Engineering, Gwangju Institute Science and Technology, Republic of Korea

Abstract. The Comprehensive Automobile Research System (CARS) is an open-source python-based automobile emissions inventory model designed to efficiently estimate high quality emissions from motor-vehicle emission sources. It can estimate the criteria air pollutants, greenhouse gases, and air toxics in various temporal resolutions at the national, state, county, and any spatial resolution based on the spatiotemporal resolutions of input datasets. The CARS is designed to utilize the local vehicle activity database, such as vehicle travel distance, road link-level network Geographic Information System (GIS) information, and vehicle-specific average speed by road type, to generate a temporally and spatially enhanced automobile emissions inventory for policymakers, stakeholders, and the air quality modeling community. The CARS model adopted the European Environment Agency's (EEA) onroad automobile emissions calculation methodologies to estimate the hot exhaust, cold start, and evaporative emissions from onroad automobile sources. It can optionally utilize road link-specific average speed distribution (ASD) inputs to reflect more realistic vehicle speed variations by road type than a road-specific single averaged speed approach. Also, utilizing high-resolution road GIS data allows the CARS to estimate the road link-level emissions to improve the inventory's spatial resolution. When we compared the official 2015 national mobile emissions from Korea's Clean Air Policy Support System (CAPSS) against the ones estimated by the CARS, there is a moderate increase of VOC (33 %), CO (52 %), and fine particulate matter (PM2.5) (15 %) emissions while NOx and SOx are reduced by 24 % and 17 % in the CARS estimates. The main differences are driven by the usage of different vehicle activities and the incorporation of road-specific ASD, which plays a critical role in hot exhaust emission estimates but wasn’t implemented in Korea’s CAPSS mobile emissions inventory. While 52% of vehicles use gasoline fuel and 35 % use diesel, gasoline vehicles only contribute 7.7 % of total NOx emissions while diesel vehicles contribute 85.3 %. But for VOC emissions, gasoline vehicles contribute 52.1 % while diesel vehicles are limited to 23 %. While diesel buses are only 0.3 % of vehicles, each vehicle has the largest contribution to NOx emissions (8.51 % of NOx total) due to its longest daily VKT. For VOC, CNG buses are the largest contributor with 19.5 % of total VOC emissions. It indicates that the CNG bus is better for the rural area while the diesel bus is better applicable for the urban area for a better ozone control strategy because the rural area is usually NOx limited for ozone formation and urban area is VOC limited region. For primary PM2.5, more than 98.5 % is from diesel vehicles. The CARS model's in-depth analysis feature can assist government policymakers and stakeholders develop the best emission abatement strategies.

Bok H. Baek et al.

Status: open (until 01 Nov 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CEC1: 'Comment on gmd-2021-135', Astrid Kerkweg, 13 Aug 2021 reply
    • CC1: 'Reply on CEC1', Bok H. Baek, 31 Aug 2021 reply
  • RC1: 'Comment on gmd-2021-135', Anonymous Referee #1, 15 Sep 2021 reply
  • RC2: 'Comment on gmd-2021-135', Darrell Sonntag, 11 Oct 2021 reply

Bok H. Baek et al.

Bok H. Baek et al.

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Short summary
The Comprehensive Automobile Research System (CARS) is an open-source python-based automobile emissions inventory model designed to efficiently estimate high quality emissions. The CARS is designed to utilize the local vehicle activity database, such as vehicle travel distance, road link-level network information, and vehicle-specific average speed by road type, to generate a temporally and spatially enhanced inventory for policymakers, stakeholders, and the air quality modeling community.