But from an environmental perspective, perhaps people are more concerned about the trade-off between carbon emissions and distance traveled. Efficiency measure

But from an environmental perspective, perhaps people are more concerned about the trade-off between carbon emissions and distance traveled. Efficiency measures would be great way to evaluate drive sources, and would perhaps be very revealing when internal combustion is exposed as being so inefficient. But perhaps a rating of carbon "moles per kilometer" would be a better indication of environmental impact of any motion source. It would be interesting to compare even with walking, running, and biking (at different speeds), as you exhale (significantly smaller) amounts of carbon dioxide (and none of the worst carbon offender, CO, thankfully). Here too, the energy source that you are plugging this module into could greatly vary your MPK.