Commission reviews new methods to count transportation emissions; staff to add Google EIE data to 2024 inventory

Zach Emerman presented analysis showing Bloomington’s present method of counting vehicle miles traveled (VMT) — which counts only mileage inside city limits — likely undercounts transportation emissions and therefore underrepresents the transportation sector’s share of the city’s greenhouse gas (GHG) inventory. He showed comparisons of three approaches (in‑boundary only, full VMT, and an induced‑traffic model aligned with the Global Protocol for Community‑Scale Greenhouse Gas Emissions — GPC) and cited peer cities that have switched methods.

"Transportation is currently 28% of our greenhouse gas emissions," Zach said, citing the national baseline to frame the local comparison, and argued that Bloomington’s transportation share (about 14% under current accounting) would rise to roughly 23% if an induced‑traffic method using Google EIE data were applied. He warned the differences matter because VMT is the baseline input: "If you have a wrong estimate on vehicle miles traveled at the beginning, everything else after it is gonna be wrong," he said.

Consultant Wes De Silvestriol (Climate Nave), who provides Bloomington’s annual GHG inventory, gave methodological context and cautioned about data limits while endorsing the approach’s practical benefits. He noted the EIE dataset tracks movements from devices using Google Maps and that Google’s ground‑truthing studies showed high correlations with roadway sensors. "The data that is needed to calculate a GPC‑compliant induced traffic emissions model is now available and freely accessible," Wes said, while also acknowledging valid critiques about reliance on a large private provider.

Commissioners pressed on timing and comparability. Zach and staff said the city received 2024 electricity data from Duke Energy and that the 2024 inventory—due in a few months—will include EIE data; staff emphasized they will run historical recalculations so year‑over‑year comparisons remain meaningful. Commissioners also asked about mode‑split and fuel type accounting; staff said registration and county vehicle data will still be used to estimate vehicle classes and fuels, and that EIE primarily supplies VMT patterns.

Members discussed tradeoffs: EIE is more granular and historical back to 2018, but partly opaque in how its algorithms are applied. Commissioners raised concerns about reliance on a private tech provider and whether changes should be applied retroactively; legal and technical staff recommended transparency in methodology and historical recalculations to preserve the inventory’s policy usefulness.

Next steps: staff confirmed they will incorporate EIE data into the 2024 inventory and perform historical recalculations so the updated induced‑traffic estimates can be compared across years. The commission suggested complementary local outreach (anti‑idling campaigns, Bloomington Energy Works recruitment) as practical measures to reduce transportation emissions.

Ending: The presentation closed to applause and moved into other agenda items; staff will publish the updated 2024 inventory when available and document methodology choices for public review.