Driving 55 mph Saves Gas?
There has been recent talk of reducing the speed limit to 55 mph in order to force drivers to be more fuel-efficient. I'm in favor of giving people the option to save gas, after being fully informed of the savings, but I'm certainly not in favor of a 55 mph national speed limit.
The numbers suggest that driving at 55 versus 70 will save gas, but this doesn't take into account certain cars which may have better fuel efficiency at different speeds. I'll go along with this theory anyway, as one person describes getting 35 miles per gallon driving at 55 mph and 25 mpg driving at 70, and see how it works.
A 100-mile trip at 55 mph will take you 1.82 hours and use 2.86 gallons of gas. The same trip at 70 mph will take you 1.42 hours and expend 4 gallons of gas. Your savings of 1.14 gallons, equivalent to $3.26, using today's national average gas price, will cost you 23.4 minutes in travel time.
I would guess that many of you would be willing to spend $3.26 to save that time, because, perhaps you time is worth more than that, considering it could be devoted to other endeavors. And we haven't even brought up traffic impact. By definition, moving slower will allow fewer vehicles to pass though a certain point over time. More traffic, more idle time, more wasted gas.
The bottom line is, this should be an individual decision based on the circumstances of a trip, time and needs, not a government imposed conservation effort.
Some reading:
http://acrosstheboard.blogspot.com/2005/10/driving-55-mph-does-save-gas-mileage.html