|
Are We Really Serious About Saving Money On Gas? |
|
|
|
Thursday, 17 July 2008 |
|
Robert L. Christensen*
Gasoline prices at this date have crept past $4 per gallon for the cheapest regular. More people are buying fuel efficient and hybrid cars, but for generations Americans have been accustomed to having bigger (and more prestigious) vehicles to haul themselves around. Both domestic and foreign car makers have begun making lighter cars to take advantage of the physical law which says that moving less weight from one spot to another takes less energy. These changes are slowly taking place. More needs to be done now.
This article has as its focus one dimension of fuel use which virtually all of us can control by adjusting our driving habits: the foot on the pedal. This affects speed and the fuel consumed by the vehicle! It’s a fact that the faster the vehicle goes, the greater the air resistance and hence the more energy required for propulsion. A few decades ago we had a national speed limit of 55 miles per hour. But, once fuel prices started to drop, public sentiment gave little support for keeping it and the trucking lobby argued that not only did the lower speeds cost more in time but that truck engines were less efficient at those speeds. And so the limits were raised again. The speed limit on most US highways is now 65 miles per hour. Of course we all know that the posted limit has become the minimum speed. Most traffic is moving at 75 mph except in congestion or around accident scenes.
As a society of commuters, we give time a high value. We’ve come to expect to get from one place to another quickly. We leave 5 to 15 minutes later than we should to get to work, school, sports, etc. The time saved is used for extra sleep, sips of coffee, watching news, and the like. Why do we travel 75 miles per hour? Because we can! Most of our major highways are capable of allowing vehicles to travel at 75 mph or more. And most of our vehicles are capable of traveling at 75 mph, or more.
There is no rational reason why any vehicle, other than police and emergency vehicles, needs to travel at such speeds. I propose that a nationwide speed limit of 55 mph be reinstated on our highways. Reducing and enforcing a 55 mph limit will offer significant savings in fuel costs to motorists, reduce the amount of oil we import, and improve our international balance of payments deficit.
So let’s get down to the nitty gritty of just what aggregate national fuel energy cost savings might be if a national 55 mph speed limit were put in effect. A 1997 US Federal Highway Administration Report cited the following miles per gallon(mpg) at three different traveling speeds: 55mph = 32.4 mpg; 65mph = 29.2 mpg; 75mph = 24.8 mpg.(1) It has been said that these US figures no longer apply because vehicles today have better fuel economy. Perhaps, but the numbers seem to reasonably approximate the published fuel economy figures for intermediate vehicles today. The relative values demonstrate that, as speed increases from 55 mph to 75 mph, fuel economy is reduced by 30.6 percent. Looked at from the other direction, reducing speed from 75 to 55 mph will reduce fuel consumption per 1,000 miles traveled by about 10 gallons or nearly $40, at $4. per gallon. If the vehicle travels 20,000 miles per year at 75mph, 200 gallons would be saved. At $4./gallon that is $800.
Currently, there are an estimated 250 million passenger vehicles in the US. If, on average, each travels 20,000 miles per year that totals to 5 trillion miles. Now assume 1 trillion of those miles are currently traveled at an average speed of 75 mph. From the above example, if 10 gallons are saved per 1,000 miles that would add up to 10 billion gallons saved (nearly $40 billion at $4./gallon). Since 2.15 gallons of oil is required to produce 1 gallon of gasoline that translates to about 21.5 billion gallons of oil. At 42 gallons per barrel that equals about 512 million barrels of oil or slightly more than 10 percent of total oil imports in 2007!!!(Total imports in 2007 were estimated to be 4.9 billion barrels.) (2)
Thus the math shows that if we reduced speed limits to 55 miles/hour, and enforced them, we would consume 10 billion gallons less fuel and US motorists would save $40 billion. At the same time, with oil import prices currently at $130/barrel, a reduction of 512 million barrels of oil could reduce US imports by $66.56 billion which is about 10 percent of our Balance of Payment deficit!!!! [For 2007 the difference between US Current Account Exports and Current Account Imports was $634 billion.] If you don’t like my assumptions, make your own and do the math.
For the individual, the time saved by speeding has a real economic cost. How much time do we save anyway? As an example consider a 20 mile commute traveled at 75 mph as compared with 55 mph: at 75 mph it will take 16.0 minutes to travel the 20 miles; at 55 mph it will take 21.82 minutes;. A saving of 5.82 minutes. At 55 mph and 32.4 mpg fuel consumption is 0.62 gallons, and at 75 mph and 24.8 mpg fuel consumption is 0.81 gallons - a difference of 0.19 gallons. At $4. per gallon the value of the additional fuel consumed is $0.76 (the amount it costs to save 5.82 minutes). Expressed in terms of fuel cost, the value of the time saved is $7.84 per hour. Put another way, driving 55 mph as compared with 75mph will save you nearly $8 for every hour of driving time . So, for the individual, the time saved by speeding has a real economic cost. A lighter foot on the pedal can save not one, but two ways!
Thus, a partial real solution to our energy problem is simple: (1) establish and enforce a 55 mph speed limit on all highways, (2) require all passenger cars and trucks to have a speed governor installed that will not allow the vehicle to exceed 58 mph. Further, discourage drivers from by-passing these limits by establishing punitive penalties for speeding - say a fine of $750 and a 6 month suspension of one’s drivers license for being clocked at more than 60 mph. A bonus would be an improvement in our Federal Balance of Payments
The math works. The question is: Do we - the people and the state and federal governments - have the will to do it?
(1)West,B.H, R.N.McGill,J.W Hodgson, S.S. Sluder, and D.E. Smith, "Development and Verification of Light Duty Model Emissions and Fuel Consumption Values for Traffic Models" FHWA Report, Washington, D.C. April 1997 and April 1998.
(2) Official Energy Statistics, US Energy Information Administration Navigator. 2007 Total Oil Imports From All Countries reports 4.905 billion barrels.
*Robert L. Christensen
Professor Emeritus, Resource Economics, University of Massachusetts, Amherst
University of Massachusetts, Amherst
|
|
|
|
