Warning: This article contains math.

Image Credit: Pat Hawks

Nothing makes me feel more American than the open road. I love the feel of the wind gusting through my remaining hair, ZZ Top blaring on the stereo, the open landscape rolling by in an endless panorama as the miles disappear beneath my wheels.

The idea of dropping my speed to the unending crawl of 55 miles per hour makes me cringe. No longer would the landscape roll by; it would sit there. The wind through my hair would turn into a gentle breeze, and I would have to trade in ZZ Top for whatever castrated emo band people listen to these days.

Of course, expressing my personal feelings is not the same as making an argument. Most European countries allow 120 or 130 kph (75 to 81 mph). So what if a 55 mph speed limit would make us drive slower than the French? Personal opinions and national shame are not careful rational reasons to resist a change that could save us gas.

So exactly how much money would this save? Let’s look at two iconic American trips: the 30-mile commute and the 600-mile road trip. Some of you on the East Coast are probably saying that a 600-mile road trip is far from typical, but cities in the Midwest are far apart.

On a 30-mile commute, if you go 75 mph in a 70 mph speed zone, your trip will take you 24 minutes. According to Department of Energy, each 5 mph over 60 costs you 30 cents per gallon extra in lost efficiency. Your 30-mile trip probably takes about 1 gallon (12 in an SUV), so it would cost you an extra 90 cents. If you traveled at 60 in a 55, the trip would take 30 minutes. Is it worth paying an extra dollar in gas to save six minutes? Unless you’re late for a big meeting, probably not. So on a commute, slowing down makes economic sense.

Now suppose you are embarking on that classic American pursuit — the road trip. I chose 600 miles for two reasons. First, it is roughly the distance from my hometown, Kansas City, to a whole list of other American cities, including Denver (605), Chicago (529), Dallas (552), Memphis (526) and Milwaukee (568). Secondly, if you average 70 mph, the above journeys will take you a little more than eight hours, which is a nice round number for a day of driving.

Let’s say you decide to drive to Denver to visit a friend. I can state from experience that in order to average 70 mph, you have to keep stops to a minimum and cruise at close to 80 mph. Most of the western speed limits are 70 or 75, so this shouldn’t be a problem. You cruise at 80 mph (skillfully avoiding those foul oblivious beings who move to the left lane and then feel it’s their personal cruising lane, where they can drive as slowly as possible without actually coming to a complete stop) to average 70, the 605-mile journey takes you eight hours and 38 minutes. At 30 mpg, it takes 20 gallons, which costs about $80. But because of the decreased efficiency, the loss of mileage will cost you $1.20 per gallon for an extra cost of $20.80.

So the trip totals are eight hours and 30 minutes in travel time, and $100 for gas (I’m ignoring the fact that traveling to Denver means going uphill, which always wrecks my gas mileage — this is just an example).

If you travel at 60 mph — the speed recommended for efficiency — your average speed will be around 55 mph because of stops. Averaging 55, the trip takes you 11 hours. Gas, as above, will be around $80.

There is extra factor. Many people, when faced with an 11-hour drive with minimal breaks and nothing but fast food, will choose to extend their travel, stop for dinner and not push as hard. This means turning it into a two-day trip, which includes a night in a hotel. The cheapest hotels I’ve seen while cruising down the interstate are $50 per night. When you add in the cost of the hotel (and you’ll probably need an extra meal) the cost of the trip becomes $130, which is more than the $100 we paid to arrive more quickly.

So for a short commute, slowing down from 75 to 70 or 65 won’t cost you that much in time, and it will save you a little money over the long haul. On a long road trip, however, the amount of money saved does not compensate for the loss of time, and it may even cost you more if you have to stay in a hotel.

Imagine a circle around your town. You can even draw it on a map if you use a pencil. In one eight-hour day of driving under current conditions, you can travel about 600 miles in any direction. This means that you can visit any city within a 1.13 million-square-mile circle around your town. That’s a lot of ground. If the speed limit drops to 55, you can cover only 440 miles in any direction. That’s a circle of only 600,000 square miles. Lowering the speed limit would reduce the area you could visit in one day by more than half a million square miles! From a Midwestern city like Kansas City, that would put all the major metropolises in the heart of the country out of reach.

There are other factors in determining a speed limit. Many people claim that slower speeds are safer. In fact, according to Time:

Since the 55-m.p.h. limit was repealed in 1995, the number of fatal motor-vehicle crashes has increased by little more than 1,000, while deaths per 100,000 licensed drivers has dipped over the same period.

Not only that, but many dangerous driving situations come not from absolute speed, but in differences in speed between drivers. If everyone is going between 70 and 85, there is only a 15 mph difference. If some people are driving 55 and others, thinking the low speed limit is some kind of practical joke, are still going 85, there is a 30 mph differential, which makes it much more difficult to avoid crashes.

That said, no one is stopping you from going 55 if you want to (as long as you’re not in my lane). It is (supposed to be) a free country after all. If you decide that the increased fuel efficiency is worth it, then turn on your signal, move into the right-hand lane and take your time.

You’ll need it.