Green on the Go

Calculating carbon footprints can involve fuzzy math: You take your best guess at distances traveled and vehicle efficiency, and hope for a good estimate of your impact on the planet. The GPS-enabled calculator Carbon Diem, set to launch this year, aims to provide more-accurate measurements with less effort. It's part of a wave of new applications, such as Avego, Ecorio, and Carticipate, designed to make low-impact transit a no-brainer. Carbon Diem loads onto location-aware mobile devices and measures speed and movement patterns--the evenness of trains, for example, or the starts and stops of buses--to track emissions associated with your chosen mode of transport. carbondiem.com