Transportation is the largest source of greenhouse gas (GHG) emissions in the United States, and personal vehicles make up 58% of all transportation emissions. One strategy for tackling emissions from these vehicles is making it easier to reach key destinations without a car. 

The Mobility Energy Productivity (MEP) tool, developed by the National Renewable Energy Laboratory (NREL) with funding from the Energy Efficient Mobility Systems (EEMS) program of the U.S. Department of Energy, measures how well residents can reach destinations in a convenient, cost-effective, and energy-efficient way. The tool overlays a city map with a grid divided into one square kilometer units and measures how many opportunities (including jobs, educational opportunities, healthcare facilities, and others) can be reached from within each unit by different modes of travel. NREL provided ACEEE with data on the efficiency of different travel modes for the 75 cities featured in the recently released 2024 City Clean Energy Scorecard. We looked at two of these cities to understand how the data can be used to explore changes in transportation access over time and among certain populations.