The other day, while waiting way too long at a drive-thru window, I wondered how much fuel I was wasting as I sat there anticipating those familiar words:  “May I take your order, please.”  One normal drive-thru visit probably doesn’t use too much gas, but multiply that by the whole country, all year long and it’s bound to add up.  So, just how much fuel do we consume waiting in drive-thru windows?

There are several ways to approach this, but we’ll see where one method takes us.  First we’ll have to make certain broad assumptions.  The average fuel consumption at idle is said to be between 0.25 and 0.30 gallons per hour for your average vehicle.  I’ll be conservative and use 0.25 gph.  

Next, we need to determine how many people are using drive-thrus.  While this is usually fast food restaurants, we can’t forget about banks, ATMs, and even drug stores.  I’m sure I’m forgetting other businesses.  To determine the number of US drive-thru visits, let’s start with the total number of adults.  A 2008 estimate states there are 228,182,000 adults in the country.  But, all adults don’t drive due to things such as age, illness, handicap, or simply not needing to.  Certainly a lot of people in Manhattan don’t even own cars.  Further, people in rural areas may not even have drive-thrus to visit!  On the other hand, 16 and 17 year olds are not classified as adults, but are definitely among those who visit drive-thrus.  These two situations cancel each other out to some extent, but I’ll again be conservative and weight the non-drivers more heavily.  Let’s take 90% of all adults and say that 205,364,000 Americans are potential drive-thru users.

The next piece of the puzzle is to define how often these “users” are, well, using.  Many people visit a bank or ATM at least once a week.  (I personally know several people that use the ATM <I>many</I> times each week.)  It’s also not out of the ordinary for people to visit a fast food drive-thru at least once a week, but there are others who never do so.  Again, erring on the low side of a reasonable estimate, I’ll say that on average every driver uses a drive-thru once a week, or 52 times a year.

The final part of the equation is the duration of a visit.  An ATM visit might be as quick as a minute, while a slow fast food drive-thru could be ten minutes if you’re patient enough to wait.  I’ll use two minutes per visit.

Now it’s math time. 



So, we could save nearly 81 million gallons of gas a year if we chose to walk inside instead of using the drive-thru window.  Is this a lot?  Not really.  The US uses an estimated 350 million gallons of gas EVERY DAY for cars, trucks, and to power other equipment.  That is, if no one used drive-thrus all year long, we would have 5.5 hours of” free” gas every 365 days.  As a percentage, drive-thrus increase the country’s gas usage by a measly 0.063%.  I guess this means Al Gore won’t be resting any time soon.

This has very little to do with the article, but it's a nice picture of the Lower Falls at Stone Mountain taken this summer.