December 11, 2008 CONGRESSIONAL RECORD — SENATE S10941 

for. His ability to make others laugh 

cannot be overstated! He has certainly 

had a lasting impact on those with 

whom he has worked over the years, 

and his cordial demeanor and welcoming smile will be missed in the 

Halls of the Capitol complex. 

On a personal note, Tucker and his 

wife Kristine recently welcomed their 

first child, Tucker, Jr., into the world 

in August. I am sure that Tucker will 

be a great father, and look forward to 

hearing about the Shumack family’s 

adventures throughout the years. 

Tucker’s departure from the Small 

Business Committee is a true loss. I 

owe Tucker a debt of gratitude for his 

phenomenal work on behalf of the 

American people. I am confidant that 

he will quickly become a well-liked and 

respected member of his new office. I 

speak for my entire staff when I wish 

Tucker well in his new job, and in all 

his future endeavors. 

f 

GOVERNMENT ACCOUNTABILITY 

OFFICE ANALYSIS 

Mr. WARNER. Madam President, earlier this summer, when gasoline prices 

were topping $4 a gallon, I asked the 

GAO to analyze potential savings from 

the establishment of a national speed 

limit. I did not prescribe what that 

speed limit should be, merely asked the 

GAO to conduct an analysis at which 

speeds vehicles were most fuel efficient 

and make a determination as to whether a national speed limit would have 

positive impacts on the conservation of 

gasoline. 

My interest in this approach to gas 

conservation was spurred by a desire 

for a measure that would provide immediate relief to the overstretched 

budgets of households across America. 

I was also dusting off a solution used in 

the past, specifically, the number of 

barrels of oil saved when a national 

speed limit was imposed in 1974 in response to the Arab oil embargo. 

Last week, I was pleased to meet 

with the GAO and hear their findings 

on the relationship between vehicular 

speed and fuel economy as well as how 

reducing the speed limit might affect 

fuel use and perhaps cost. 

While the days of my service in the 

U.S. Senate are numbered, it is my 

hope that these findings by the GAO 

can serve as a useful tool to my colleagues who will return in the next 

Congress, as I know the interlinked 

issues of energy, transportation, and 

climate change are going to remain the 

focus of much debate and policy making in the coming years. 

Mr. President, I thank the GAO for 

its work, and I ask unanimous consent 

that GAO analysis be printed in the 

RECORD. 

There being no objection, the material was ordered to be printed in the 

RECORD, as follows: 

Energy Efficiency: Potential Fuel Savings Generated by a National Speed Limit Would Be 

Influenced by Many Other Factors 

In response to Senator Warner’s interest in 

obtaining information on the possibility of 

using a national speed limit to reduce fuel 

consumption, the Government Accountability Office reviewed existing literature 

and consulted knowledgeable stakeholders 

on the following: 

What is the relationship between speed and 

the fuel economy of vehicles? 

How might reducing the speed limit affect 

fuel use? 

Due to a limited time frame of two months 

to complete the work, to address these objectives, we limited our analyses to light-duty 

vehicles, such as cars, sport utility vehicles, 

and pickup trucks and relied on the expertise 

of GAO and knowledgeable stakeholders to 

identify the most relevant economic and 

transportation literature. We provided a 

draft to the three agencies whose officials we 

consulted for our analyses—the Environmental Protection Agency (EPA), the Department of Energy (DOE), and the Department of Transportation (DOT)—and incorporated relevant technical comments. We did 

not examine other aspects of implementing a 

national speed limit, such as potential safety 

impacts. In summary, we found the following. 

According to Literature and Stakeholders, Reducing a Vehicle’s Speed Can Potentially 

Increase Its Fuel Economy, Depending on 

the Vehicle’s Characteristics 

For a vehicle traveling at high speed, reducing its speed increases fuel economy. In 

general, at speeds over approximately 35 to 

45 mph, if a vehicle reduces its speed by 5 

mph, its fuel economy can increase by about 

5 to 10 percent, because air resistance, or 

drag, increases exponentially as a vehicle 

goes faster. Conversely, air resistance diminishes more rapidly as a vehicle slows down, 

thus increasing its fuel economy. 

According to existing literature and 

knowledgeable stakeholders, there is no single speed that optimizes fuel economy for all 

vehicles. Optimal speed for fuel economy for 

individual vehicles ranges widely, but is generally between 30 and 60 mph, depending on 

a vehicle’s characteristics. For example, according to the most recent published data— 

a 1997 study by Oak Ridge National Laboratory, commissioned by the Federal Highway 

Administration (FHWA), that examined fuel 

economy at different speeds for nine automobiles and light trucks from model years 

1988 through 1997—the optimal fuel economy 

for a 1994 Jeep Grand Cherokee, a sport-utility vehicle, would be about 26 miles per gallon at a steady 40 mph. In contrast, in a 2008 

internal study by the Argonne National Laboratory for the Department of Energy (DOE), 

examining four vehicles, the optimal fuel 

economy for a 2005 Toyota Echo, a subcompact car, is about 69 miles per gallon, 

achieved when traveling at a steady 30 mph. 

However, a vehicle’s fuel economy also depends on other factors besides air resistance. 

Factors that enhance fuel economy include 

engine efficiency enhancements (e.g., fuel injection), electronic and computer controls, 

more efficient transmissions, and hybrid 

technology. However, other factors, such as 

increased vehicle weight, decrease fuel economy. 

In general, over the last 2 decades, fuel 

economy gains resulting from advances in 

automotive technologies have largely been 

offset by increases in vehicle weight, performance, and accessory loads. Specifically, 

vehicles are heavier than in the past, because they are larger and include more technologies. For example, average vehicle 

weight has increased from 3,220 pounds in 

1987 to 4,117 in 2008, according to the Environmental Protection Agency (EPA). In addition, trends show that recent vehicles, on 

average, have bigger, more powerful engines 

that yield better performance—i.e., acceleration and greater speed—at the expense of 

fuel economy. For example, according to the 

same EPA report, average horsepower has increased from 118 to 222 over the same period. 

Further, increased accessory loads, such as 

air conditioning and electronics, have also 

reduced fuel economy. According to EPA, 

from 1987 through 2004, on a fleetwide basis, 

technology innovation was utilized exclusively to support market-driven attributes 

other than fuel economy, such as performance. Beginning in 2005, however, according 

to EPA’s analysis of fuel economy trends, 

technology has been used to increase both 

performance and fuel economy, while keeping vehicle weight relatively constant. 

According to Literature and Stakeholders, a Reduced Speed Limit Is Only One of Many 

Factors That Could Affect Total Fuel Use 

Lowering speed limits can potentially reduce total fuel consumption. According to 

literature we reviewed examining the impact 

of the national speed limit enacted in 1974, 

the estimated fuel savings resulting from the 

55 mph national speed limit ranged from 0.2 

to 3 percent of annual gasoline consumption. 

According to DOE’s 2008 estimate, a national 

speed limit of 55 mph could yield possible 

savings of 175,000 to 275,000 barrels of oil per 

day. This range is consistent with estimates 

of the impact of the past national speed 

limit. According to the Energy Information 

Administration, total U.S. consumption of 

petroleum for 2007 was about 21 million barrels of oil per day. 

However, other factors, including drivers’ 

compliance with a reduced speed limit, 

would affect the actual impact of a lower 

speed limit on the amount of fuel savings. 

Reducing the speed limit does not necessarily mean that drivers will comply. In 

fact, in 1975, under the previous national 

speed limit, about half of the states reported 

more drivers exceeding the national speed 

limit of 55 mph than complying with it. 

States may vary in their ability to enforce 

the reduced speed limit, in part due to cost 

and limited resources, affecting driver compliance. Moreover, a national speed limit 

would not affect many of the miles driven in 

the United States, such as those in urban 

areas, where most vehicles are already traveling at lower speeds due to lower speed limits or congestion. According to FHWA, fewer 

than one quarter of the vehicle miles traveled (VMT) in the United States would likely 

be directly affected by a changed speed limit. 

In addition, congestion forces some vehicles 

to travel slowly, no matter what the speed 

limit, meaning a reduction would have little 

or no impact on fuel consumed on congested 

roads. 

Other external conditions also affect fuel 

economy, such as road conditions, including 

whether a road is steep or flat, and weather 

conditions, including wind speed and direction. Finally, other aspects of driver behavior may also affect fuel consumption. For example, driver behavior may be affected by 

fuel prices. Higher prices may cause people 

to drive less or purchase more fuel-efficient 

vehicles. Similarly, driving at a consistent 

speed can reduce fuel consumption. In contrast, aggressive driving such as accelerating 

or stopping quickly can increase fuel consumption. In addition, proper vehicle maintenance—including regularly changing automobile fluids and filters and properly inflating tires—improves fuel economy. 

The speed limit is only one tool among 

many for potentially conserving fuel. Certain realities such as congestion on our nation’s roads, how people drive and maintain 

their vehicles, and emerging technologies 

are other potential considerations as the nation looks for options to conserve fuel.