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Chapter 5: Safety, Energy, and Environmental Impacts of Passenger Travel

The number of passenger transportation fatalities has declined in recent decades. Compared to 1990, there were about 12,500 fewer fatalities in 2014—94.6 percent of this reduction is attributable to highway travel. Highway safety enhancements, which include human factors, roadway design and maintenance, and advanced safety technologies, have contributed significantly to this decline. However, early estimates indicate an uptick in highway deaths for 2015, with preliminary data showing a 7.7 percent increase in fatalities—a marked departure from what had been a general downward trend.

Table 5-1 Fatalities by Selected Passenger Transportation Mode: 1990, 2000, 2010, and 2014


Between 1990 and 2014, the highway fatality rate, measured by deaths per 100 million vehicle-miles of travel, declined 48.1 percent. The number of passenger car and light-truck occupant fatalities fell 49.6 percent during this period. Measuring by fatalities per capita, the nonoccupant fatality rate declined 39.1 percent. During this same period, the general aviation fatality rate, measured by fatalities per 100,000 flight hours, decreased by 51.3 percent, while the fatality rate for air carriers remained stable and low. Between 1997 and 2014, the passenger rail fatality rate, measured by deaths per million train-miles, decreased by 32.6 percent.

Figure 5-1 Fatality Rates for Selected Transportation Modes: 1990–2014

Highway fatalities in 2014 were concentrated along the major corridors in the highly populated areas of California, Florida, Illinois, Texas, and throughout the populous Northeast region from New England, near Boston, MA, down to the Middle Atlantic region, near Washington, DC. In addition, fatalities were also highly concentrated along major highway corridors and around urban areas in the South Atlantic region.

Figure 5-2 Highway Crash Fatalities: 2014

A Half Century of Highway Safety Innovations–1966 to 2016

As in 2000, the number of males killed on U.S. highways exceeded the number of female fatalities for most age groups in 2014. Overall, males comprised 68.3 percent of highway fatalities in 2000 and 71.5 percent in 2014. Persons under the age of 30 continued to have the highest fatality numbers in 2014, although deaths for that age group have declined significantly. The number of highway fatalities for males in their mid-40s to late 60s (i.e., today’s baby boomers1) was higher in 2014 than it was for the men who were in the same age group in 2000. Compared to their 2000 cohorts, the 2014 baby boomers comprised a larger share of the population and drove more miles—factors that likely contributed to the higher number of fatalities.

Figure 5-3 Number of Highway Fatalities by Age and Gender: 2000 and 2014

Since 2000 there has been a considerable decrease in highway fatalities per capita across all age groups for both genders. The greatest numbers of fatalities per capita in both 2000 and 2014 were among males between the ages of 18 and 22 and over the age of 80. Female fatalities per capita in both 2000 and 2014 peaked for those between the ages of 16 and 21 and also for those over the age of 80. The 2000 rates were again higher.

Figure 5-4 Rate of Highway Fatalities by Age and Gender: 2000 and 2014

The National Highway Traffic Safety Administration estimates that 9.9 percent of highway fatalities in 2014 involved drivers who were distracted by such activities as using a cell phone, texting, eating or drinking, using navigation systems or a map, or grooming themselves. In 2015 primary laws banning texting for all drivers became effective in Oklahoma and Mississippi. As of February 2016, 46 states and the District of Columbia had laws banning texting while driving, and 14 states and the District of Columbia prohibit driver use of handheld cell phones.

Figure 5-5 State Laws on Distracted Driving Ban on Hand-Held Devices and Texting While Driving: February 2016

Alcohol-related highway crashes accounted for 11,819 deaths in 2014, down 32.0 percent from 2000. The percent of alcohol-related fatalities also decreased from 41.4 percent in 2000 to 36.2 percent in 2014.

Figure 5-6 Number and Percent of Alcohol-Related v. Nonalcohol-Related Highway Fatalities: 2000–2014

Alcohol can also impair a boater’s judgment, balance, vision, and reaction time. The U.S. Coast Guard reported 108 alcohol-related recreational boating fatalities in 2014, representing 17.7 percent of all recreational boating fatalities.

Figure 5-7 Number and Percent of Alcohol-Related v. Nonalcohol-Related Recreational Boating Fatalities: 2001–2014

Box 5-A Fatality Definition by Mode


Compared to 1990, there were 27.9 percent fewer passenger transportation injuries in 2014. As for fatalities, the majority of passenger transportation injuries are highway-related, accounting for 99.0 percent of all injuries in 2014. Much of the decrease in highway-related injuries occurred between 2000 and 2010, when the number of injuries declined 27.5 percent. Injuries among passenger-car occupants were down 45.6 percent from 1990 to 2014, but up 3.1 percent from 2010 to 2014.

Table 5-2 Injured Persons by Selected Passenger Transportation Mode: 1990, 2000, 2010, and 2014

The 2014 total highway injury rate was about half the 1990 rate. Injuries for passenger car and light-truck occupants were down 44.4 percent during this period. Measured by injuries per capita, highway nonoccupant injuries per capita declined 45.2 percent. The U.S. air carrier injury rate remained low and stable. While the general aviation injury rate decreased by 8.4 percent over this same period, it remained 10 times higher than that of air carriers. Between 1997 and 2014, the passenger rail injury rate, measured by deaths per million train-miles, decreased by 18.4 percent.

Figure 5-8 Injury Rates for Select Transportation Modes: 1990–2014

Passenger Travel and Energy

In 2013 transportation used about 26 quadrillion Btu of energy, making it the second largest sector for fuel and electricity consumption. Highway use continues to dominate transportation fuel consumption, accounting for 83.2 percent of total energy use. Light-duty vehicles (consisting of passenger cars, light trucks, vans, and sport utility vehicles) accounted for the largest share of energy use at 59.2 percent.

Figure 5-9 Energy Use by Transportation Mode: 2013

Certified air carriers experienced the largest total decrease in fuel consumption, consuming about 3.6 billion fewer gallons of jet fuel in 2014 than in 2000.  Additionally, water modes powered by residual fuel oil also showed a large decrease, declining by nearly 2.6 billion gallons during the same period.  This is likely due to many factors, including the economic recession, a shift to larger vessels, and increases in fuel efficiency.  General aviation gasoline showed the largest percent decrease in fuel consumption from 2000 to 2014, declining by 40.8 percent.  The shift from piston powered to jet fuel powered turbine engines is likely a factor that contributed to this reduction.  Consistent with increases in vehicle-miles traveled, light-duty highway vehicles used about 430 million more gallons of gasoline in 2014 than in 2000.

Table 5-3 Fuel and Electricity Consumption by Transportation Mode: 2000, 2010, and 2014

However, some transportation modes, such as transit, have showed increases in energy consumption.  This is likely attributable to several factors, such as increases in transit use as well as additional vehicles and extended transit facilities, routes, and services as shown in table 3-9 in chapter 3.
The energy intensities of passenger modes, or the energy used per passenger-mile, generally have declined over time except for those of light-duty highway vehicles. After light-duty highway vehicles, transit motor buses typically use the most energy per passenger-mile (although this can vary), followed by certificated air carriers and Amtrak.

Figure 5-10 Energy Intensity of Passenger Modes: 1990–2014

The average fuel efficiency of the total U.S. passenger-car and light-truck fleet improved by 30.0 and 26.4 percent, respectively, since 1990 as new vehicle efficiency increased. Stricter CAFE standards for fuel efficiency in passenger cars and light trucks have pushed automakers to produce vehicles with better fuel efficiency. The fuel efficiency of new passenger cars rose by 30 percent, from 28.0 mpg in 1990 to 36.4 mpg in 2014. New light trucks, which include vehicles such as pickup trucks, minivans, and SUVs, increased 26.4 percent from 20.8 mpg in 1990 to 26.3 mpg in 2014.

Figure 5‑11 Average Fuel Efficiency of U.S. Passenger Cars and Light Trucks: 1990–2014

The Corporate Average Fuel Economy (CAFE) standards were enacted by Congress in 1975. Before 1975 personal vehicle travel and fuel use typically moved in similar trajectories. Fuel economy improvements after 1975 broke this close connection as the amount of fuel used per vehicle-mile of travel steadily decreased. The gap widened further as higher miles per gallon vehicles came to dominate the on-road fleet. Also, economic cycles can influence passenger travel, which, in turn, influences overall fuel use. Economic downturns generally lead to slower growth in vehicle-miles traveled, resulting in slower increases in fuel consumption or even reductions. However, between 2013 and 2014 both vehicle travel and fuel consumption grew to comparable levels seen before the recession in 2007, increasing by 1.2 percent to 2.7 trillion miles and 2.3 percent to 126.6 billion gallons.

Figure 5-12 Vehicle-Miles of Travel and Fuel Use by Personal Vehicles: 1965–2014

Passenger Travel and Air Emissions

The transportation sector is the second largest producer of greenhouse gas (GHG) emissions, accounting for 26.4 percent of total GHG emissions in 2014. Carbon Dioxide (CO2), which is produced by the combustion of fossil fuels in internal combustion engines, is the predominant GHG emitted by the transportation sector.

Figure 5-13 Transportation-Related Greenhouse Gas Emissions: 2014

GHG emissions generally track transportation energy use because fossil fuels are the primary source of transportation energy. Passenger cars use the largest share of fuel and emit the largest share of CO2. The other largest CO2 emitters that support passenger travel are light-duty trucks, aircraft, ships and boats, other, rail, and buses. Total transportation CO2 emissions peaked in 2007 and have since steadily declined. By 2014, CO2 emission levels for all transportation modes decreased by 9.2 percent compared to 2007. From 2007 to 2014, CO2 emissions from passenger cars and light duty trucks declined by 9.6 and 7.9 percent, respectively.

Figure 5-14 CO2 GHG Emissions by Mode: 1990–2014


1 baby boomer refers to persons born in the United States between the mid-1940s and mid-1960s.