The other day I stopped at the bank to get some cash. The particular branch I chose to patronize had a drive through window, and I watched the action for a few minutes. I saw a Hummer (H2) use the window and it set me to thinking about the motivation.
In an earlier post I gave some fairly detailed estimates of the consequences of drive through windows, estimating that if they all went away we could save about 350,000 barrels of oil per year. Clearly, this is not a huge amount. What about the Hummer pilot?
The engine is a 6.0 liter V8. My Grand Cherokee has a 4.8 liter V8 and uses about 0.38 gallons per hour at idle. It seems very reasonable to assume that fuel consumption at idle is directly proportional to engine displacement so I'll estimate that the H2 uses (6.0/4.8)*0.38=0.475 gallons per hour at idle.
I don't know what the driver's bank transaction was but let's assume that it was something she (I saw that it was a woman - no implications intended) could have done at the walk-up ATM. This matters since it is clearly worth more to avoid going inside the bank than to avoid the walk-up ATM.
I think the estimates I made for times at a window in my earlier post would be applicable here, so I'll say that she burned a net three minutes worth of fuel that could have been saved had she parked and walked up. That three minutes of pistons going up and down in cylinders used about .024 gallons of fuel which cost about $0.074. So her use of the drive through meant that it was worth at least about seven cents to avoid going to the trouble of parking and walking to the ATM.
I'll guess that she might use some sort of drive through window four times per week, so she might burn about five gallons of fuel per year while driving through, worth about $15.00. If she were to be presented with these numbers, do you suppose she'd immediately cease use of the drive through? I'm thinking that this is one of the few answers of which I can be sure. Actually, she'd have two answers: "no" and "HELL NO!!"
I wonder where her "point of indifference" would be? Surely she wouldn't use the drive through if it cost, say, $100.00 per use versus the walk-up ATM. What about $10.00? $1.00? I'm going to hypothesize that an average H2 driver would drive through for a dollar and walk up if the price differential were any higher. That would imply that a gas price of (100/7.4)*3.12=$42.16 per gallon would be the threshold of removing her from her car. There's a lot of room for gas prices to go up before certain lifestyle choices would change. I don't think drive through windows will be shuttered anytime soon.