Lifecycle Environmental Impact
Take a look at the chart and graph below which assume hypothetical (unit-less) environmental impacts from making a vehicle, operating it for ten years, and scrapping it. The numbers aren’t important. What is the important is the concept.
If it hasn’t already been done this kind of information should be compiled in order to provide us with a useful method to directly compare the impact of each vehicle model. The information could come from combining studies of the manufacturers and their processes, the average miles driven per year for each model and their average life spans, and studies on vehicle scrap. Surely between the in-use estimates could come from various state motor vehicle departments and information services such as Carfax.
The most relevant figure to derive from this data then is the environmental impact per unit of work. For passenger cars that metric is VMT (Vehicle Miles Traveled) or perhaps passenger miles traveled. VMT is much easier to calculate. The passenger miles may be more accurate, but it is virtually impossible, certainly impractical, to determine how many occupants are in a car over what portion of total mileage a vehicle accumulates.
When figures from different vehicles over their lifetimes and distances traveled are compared, one conclusion will likely stand out. Lighter vehicles will have less environmental impact overall. It takes less to manufacture them, propel them, and ultimately to scrap them (see my post on longer automotive lifecycles).
Let’s not lose sight of the total picture. Assuming environmental impact is greatest from vehicle manufacturing relative to operating them, it makes great sense to lengthen the duration of their lifecycles, especially if they can be periodically upgraded to reduce in-service emissions output.