What Are the Different Measures of Mobility Telling Us About Surface Transportation CO₂ Emissions During the COVID‐19 Pandemic?

Abstract

The COVID‐19 pandemic led to widespread reductions in mobility and induced observable changes in atmospheric emissions. Recent work has employed novel mobility data sets as a proxy for trace gas emissions from traffic by scaling CO2 emissions linearly with those near‐real‐time mobility data. Yet, there has been little work evaluating these emission numbers. Here, we systematically compare these mobility data sets to traffic data from local governments in seven diverse urban and national/state regions to characterize the magnitude of errors that result from using the mobility data. We observe differences in excess of 60% between these mobility data sets and local traffic data. We could not find a general functional relationship between the mobility data and traffic flow over all the regions and observe higher deviations from using such general relationships than the original data. Finally, we give an overview of the potential errors that come from estimating CO2 emissions using (mobility or traffic) activity data. Future work should be cautious while using these mobility metrics for emission estimates.

Tropospheric NO2 and O3 Response to COVID‐19 Lockdown Restrictions at the National and Urban Scales in Germany

“…These actions include physical distancing, a ban on large group gatherings, home office work, and international and domestic travel restrictions (DW COVID‐19, 2020 ). These measures resulted in a significant reduction in emissions following economic activity and overall mobility (Evangeliou et al., 2021 ; Gensheimer et al., 2021 ; Guevara et al., 2021 ; Le Quéré et al., 2020 ; Z. Liu, Ciais, et al., 2020 ; Z. Liu, Deng, et al., 2020 ; Turner et al., 2020 ). There has been a lot of interest in studying this time window and its impacts on the Earth system.…”

Dramatic Lockdown Fossil Fuel CO2 Decrease Detected by Citizen Science-Supported Atmospheric Radiocarbon Observations

“…The slightly larger reduction in traffic implied by the Apple Mobility Data than in our CO 2ff observations could be because changes in driving requests are not an exact proxy for emission changes. 29 …”

Observations of Volatile Organic Compounds in the Los Angeles Basin during COVID-19

“…The samples were analyzed for VOCs using one-dimensional gas chromatography (GC) with multiple detectors (including flame ionization (FID), electron capture (ECD), and mass spectrometry (MSD)) and two-dimensional gas chromatography with time-of-flight mass spectrometry (GC/GC-TOF-MS). Changes in mobile source patterns were well documented during LAAQC. − Using traffic counts obtained from Caltrans as one metric, travel across the LA Basin during LAAQC began at only ∼55% of pre-COVID levels and increased approximately linearly to ∼80% by the end of the campaign . Other changes in human activity associated with urban emissions (e.g., ordering takeout, using personal care and cleaning products, using motorized landscaping equipment, etc.)…”