TRANSPORTATION SECTOR

Summary

Energy consumption in the transportation sector has increased rapidly since 1970. Primarily because of increased vehicle travel, transportation energy consumption grew at the rate of 3.1 percent per year between 1970 and 1993. Vehicle travel in Washington State increased from 20 billion miles in 1970 to nearly 48 billion miles in 1993, an increase of 3.8 percent per year. This was only partially offset by increases in vehicle fuel efficiency. While vehicle travel grew by 135 percent, the fuel efficiency of the average highway vehicle increased only 36 percent between 1970 and 1993, from 12.2 miles per gallon in 1970 to 16.6 mpg in 1993. However, highway energy expenditures declined nearly 30 percent since 1981 due to a large drop in real gasoline prices. The combination of increased vehicle fuel efficiency and lower gasoline prices resulted in the average fuel cost of driving a mile declining nearly 56 percent from 1981 to 1993.

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Why This Indicator?

The transportation sector indicators focus on highway fuel consumption. Highway vehicle fuels account for over 60 percent of transportation sector energy consumption, and are perhaps the most familiar trends to most people. The balance of transportation energy consumption is made up principally of jet fuel (22 percent) and residual fuel oil (14 percent).

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What Are The Trends?

Vehicle miles traveled (VMT) have increased rapidly and steadily since 1970. Total VMT has increased more than two percent in each year except 1974, 1980 and 1993. On a per capita basis, VMT grew by more than 50 percent between 1970 and 1993, from nearly 6,000 to over 9,000 miles per Washington resident. Highway vehicle fuel efficiency has not kept up. From a low of 11.4 miles per gallon (mpg) in 1976, fuel efficiency has increased at 2.2 percent per year to 16.6 mpg in 1993.

Highway energy expenditures in the transportation sector reached a high of $4.8 billion in 1981 and have since declined by nearly 30 percent. The decline in highway fuel expenditures occurred despite the fact that VMT rose by 62 percent over the same period. This is due to the precipitous drop in gasoline prices over that period. Corrected for inflation, the price of gasoline dropped by nearly one half between 1981 and 1993. After peaking in 1981 at 16.2 cents per mile, the average fuel cost of driving a mile declined 56 percent to seven cents per mile in 1993.

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What Does It Mean?

Energy consumption in the transportation sector continues to increase rapidly in Washington, despite gains in vehicle fuel efficiency. The reason is that people are simply driving more and more miles each year. Vehicle miles traveled per capita increased by over 50 percent between 1970 and 1993. This trend, combined with the rapid increase in the state's population during the same period, has resulted in total highway VMT more than doubling, from 20 billion miles in 1970 to nearly 48 billion miles in 1993.

The primary cause of the continuing growth in vehicle travel is the shifting land-use patterns that have characterized the United States and Washington State in the latter half of the 20th century. Rapid growth in suburban and, more recently, remote ex-urban areas has resulted not only in longer commute trips, but in longer trips to the grocery store, the movies, etc. These trends in land-use patterns would likely not have occurred without inexpensive gasoline. With the exception of the period between 1973 and 1985, when prices were inflated due to the influence of the OPEC cartel, real gasoline prices have been falling consistently since the Second World War (see box entitled "Gasoline Prices Since the 1950s"). With increasing fuel efficiency and improved vehicle technology, the real cost of driving has declined even more sharply.

Because increasing vehicle travel is a long-term trend due in large part to shifting land-use patterns, there is probably very little that can be done to reverse the trend. The fact that VMT per capita declined slightly after the oil shocks of 1973 and 1979 indicates that consumers do have some leeway to respond to increasing gasoline prices. However, as the chart shows, the large spikes in the cost of driving in those years resulted in very small declines in vehicle travel. These are just blips in the historical trend towards lower driving costs and higher vehicle travel.

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About The Data

Highway energy consumption includes all gasoline and diesel used in the transportation sector. This necessarily includes small amounts of diesel used by trains and ferries. Energy consumption and expenditure data are from the Energy Information Administration, while VMT data are from the Washington State Department of Transportation. Fuel efficiency represents miles per gallon for all highway vehicles in the state, including trucks, buses and motorcycles as well as automobiles, and is determined by dividing total highway miles by total gasoline and diesel consumption. The fuel cost of driving is simply gasoline and diesel expenditures divided by vehicle miles driven.

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