It is generally accepted that auto fuel consumption goes up as speed increases. The national speed limit was reduced to 55 mph in the 70s to reduce oil consumption. It was allowed to rise when oil became plentiful again and prices declined. It’s time, I believe, to reduce speed limits again.
I recently made some measurements of speed and fuel efficiency with my own car, a Honda Civic. On a relatively level interstate highway an increase in average speed from 60 to 70 miles per hour increased the gas consumption by 11%. I expect other cars would show similar results. Truck data would probably be more dramatic.
To read more about the data and analysis go to spreadsheet.
I recommend that we all reduce our driving speeds and thereby reduce our fuel consumption. This will reduce our dependence on foreign oil, and reduce the generation of carbon dioxide and slow global warming.
What do you think? Should we mandate lower speeds by state or national law? Could we?
Bill Allen, July 29, 2007