To reach its goal of seeing environmentally unhealthy emissions of greenhouse gases from heavy duty vehicles reduced to net zero in the next two decades, California must set early retirement dates for these vehicles. That’s the conclusion of a study by Stanford University and ASU researchers published in the journal “Environmental Research: Infrastructure and Sustainability.” Eleanor Hennessey, a postdoctoral scholar in the School of Sustainable Engineering and the Built Environment, part of the Fulton Schools, is the study’s main author. The research findings are relevant to all countries trying to decarbonize motor vehicles to protect the health of their citizens. Many U.S. states have carbon neutrality goals similar to those set by California.