“Be kind, for everyone you meet is fighting a hard battle” - Often attributed to Plato but likely from Ian McLaren (pseudonym of Reverend John Watson)

## Tuesday, April 24, 2007

### At what point will fuel prices justify low speed?

The last couple of posts have dealt with the trade off between the value of the fuel saved at low speeds versus the value of the time "wasted." I determined that, for my trip, at my salary, in my vehicle, at $3.40/gallon for gasoline, the speed at which my total cost (my salary + fuel to make the trip) was minimized is 110 m.p.h. Clearly not practical,especially if everyone ran a similar calculation and decided to drive at what I will call their "minimum total expenditure speed (mtes)." But the process and the mathematics of determining those numbers led me to wonder what gasoline price would make the fuel savings balance the time costs at reasonable speeds. It turns out that the number is extremely high. For example, for gas at$5.00/gallon, the mtes is 97 m.p.h. At \$8.00/gallon, the mtes is 87 m.p.h. The mtes never gets to the most efficient speed because the m.p.g. as a function of speed curve is fairly flat in the range near the maximum, which I determined analytically to be 50.8 m.p.h. for the Grand Cherokee Limited.

It is reminiscent of the earlier post where I contemplated the point of indifference for a woman in a hummer at the bank drive-through window. There, as here, the gasoline price that would economically cause a behavioral change was ludicrously high.

There are many actions that can be taken to reduce consumption, some of which do not have the down side associated with maximally efficient freeway speeds. And there are forms of income other than monetary, so-called "psychic income." This involves benefits such as fulfilling the desire to protect the environment, feeling as if one is doing the best one can to leave a better world for one's children, and other non-monetary considerations that comport with one's philosophy or desires. In my case, it has been the satisfaction of pursuing the goal of minimization of fuel consumption for its own sake. Some call me obsessive, and they are probably correct.

These things are difficult, if not impossible to quantify in a meaningful way, other than the extent to which someone is willing to forgo things that can be quantified to receive the benefit. In my case, it is clear that the enjoyment of running the experiment and writing about it in this blog compensates me for the opportunity cost of getting to my destinations more slowly.