Hybrid cars have become so eco-friendly they now trump at least one form of human locomotion. Alberto E. Minetti, professor of physiology at the University of Milan, along with his master’s student Gaspare Pavei, compared the CO 2 emissions of four men walking, running and biking with the emissions of a hybrid vehicle carrying those same four men. The scientists found that four men would release more CO 2 by jogging than if they boarded a hybrid car. (On average, four women jogging would release less CO 2 than if they rode in a car because of their lower body mass.) The lesson: next time you and three male friends are late for the movies, don’t run. Hail a hybrid taxi.