Several things we know with absolute certitude about the evolution of vehicles over the past century: vehicles are safer; vehicles are generally faster and more capable; vehicles offer better fuel economy than in earlier decades, and so forth.
Well, it turns out that the third item on the list mightn’t be as true as we’d all like to believe. Citing a study conducted by the University of Michigan Transportation Research Institute, Autoblog reports that since 1923, fleet-wide fuel economy across the United States has increased a mere 3.6 miles per gallon, from 14 to 17.6 mpg.
Granted, data regarding fuel economy aren’t consistently available throughout history; instead, the UMTRI calculated fleet-wide fuel economy for those years from the total miles driven, and total gallons of gas consumed. Furthermore, it hardly seems fair lumping passenger cars in with medium- and heavy-duty trucks, especially considering how much more we haul on the road today than we did in 1923. But that’s exactly what the US DOT did from 1923 to 1935, and it was only in 1966 that the DOT finally separated trucks from lightweight to heavy-duty, according to Autoblog.
And then, there’s the simple fact that with regard to transporting freight especially, vehicles are much more capable than they used to be. In other words, two vehicles with equal fuel economy from two different decades will have two very different levels of performance. If today’s tractor units only hauled the same mass as decades ago, their fuel economy numbers might be far higher, but so would the number of miles driven (more trips).
Some other interesting data:
- From 1923 to 1973, overall fuel economy decreased from 14 mpg to 11.9 mpg.
- Fuel economy then increased to 16.9 mpg in 1991, and on to 17.6 in 2013.
- Fuel economy of passenger cars alone increased from 13.4 mpg in 1973, to 23.4 mpg in 2013.
- Overall, the fuel economy of lightweight vehicles (passenger cars, light-duty trucks, motorcycles) rose 8.7 mpg since 1966.