Growing demand for freight transportation heightens concerns about its safety, energy consumption, and environmental impacts. While safety in all freight modes continues to be monitored actively, the availability of energy consumption data has declined with the discontinuation of the Vehicle Inventory and Use Survey.
While the amount of freight transportation activity has increased, the total number of related fatalities declined by 23.8 percent from 2000 to 2015. All modes have substantially reduced the number of fatalities over that period. Trucks accounted for 87.8 percent of all freight transportation fatalities and 11.6 percent of all highway fatalities in 2015. The vast majority of fatalities involve passenger travel on highways.
According to the National Highway Traffic Safety Administration, the number of total highway fatalities in 2015 grew by 7.2 percent (2,348) over the 2014 level. This was the first annual increase in highway fatalities since 2012 and the greatest annual fatality total since 2008. Large-truck occupant fatalities increased by 1.7 percent, from 656 in 2014 to 667 in 2015.
From 1990 through 2015, the overall rate of highway fatalities per vehicle-miles of travel (vmt) declined by 47.1 percent as the highway modes showed across-the-board reductions. Fatalities per vmt for large truck occupants decreased by 58.5 percent.
Historically, freight transportation comprises a relatively small percentage of all transportation-related injuries—4.6 percent in 2000 versus 4.9 percent in 2015. However, of the freight-transportation injuries that do occur, the majority of them are attributable to the highway mode—94.6 percent in 2000 versus 96.4 percent in 2015. These ratios have remained relatively steady from year to year despite a drop of 775,725 (24.1 percent) in the estimated number of all transportation-related injuries during the 2000 to 2015 time period.
Because most hazardous materials are transported by truck, the majority of incidents related to the movement of hazardous materials occur on highways or in truck terminals. A very small share of hazardous materials transportation incidents are the result of a vehicular crash or derailment (referred to as “accident related”). While 1.5 percent of the incidents in 2016 were accident related, they accounted for 64.3 percent of all property damage. Highway had the highest share of incidents at 90.4 percent but accounted for 60.9 percent of all property damage.
The safety fitness of motor carriers is a top priority of the U.S. Department of Transportation. As part of its efforts to improve safety, federal and state governments conducted 7,576 safety compliance reviews in 2016. Of that total, about 6.1 percent (460) of motor carriers that were subject to the review received an unsatisfactory rating. If a carrier gets a conditional rating, it means that there are conditions that need to be met for the carrier’s operations to be in full compliance. Once the conditions have been met, the carrier would need a new ratable review to get the rating upgraded to satisfactory. An unsatisfactory rating implies that there are serious deficiencies that need to be rectified within 45 – 60 days. If rectified, the rating can be upgraded to a conditional or satisfactory rating. If not, the provisional unsatisfactory rating becomes final and the carrier is placed out-of-service.
About one-fifth of all roadside inspections of commercial vehicles resulted in a vehicle being placed out of service (OOS) for a serious violation. Much lower percentages of driver and hazardous materials inspections resulted in OOS orders. In 2016, 4.9 percent of driver inspections and 3.9 percent of hazardous materials inspections resulted in OOS orders.
While truck vehicle-miles traveled decreased by 8 percent over the 2007 to 2015 period, truck fuel consumption declined by 7.4 percent, from 47.2 billion gallons to 43.7 billion gallons. Fuel use in Class I freight railroads declined by 8.9 percent, from 4.1 billion gallons in 2007 to 3.7 billion gallons in 2015. These decreases occurred despite growing numbers of trucks and Class I locomotives in recent years (table 3-4).
In 2015 freight truck accounted for a majority of freight transportation energy consumption, followed by water, a distant second.
Miles per gallon of single-unit trucks (based on total travel and fuel consumption) have been relatively stable over the 2007 to 2015 period. Despite this small change in fuel efficiency, fuel consumption dropped as single-unit trucks traveled fewer miles overall and fewer miles per vehicle.
Miles per gallon of combination trucks (based on average miles traveled and fuel consumption) remained stable between 2007 and 2015. During the same period, vehicle-miles traveled by combination trucks declined by about 14.0 billion (about 7.6 percent).
Energy intensity is the amount of energy used to produce a given level of output or activity which is measured by vehicle-miles, freight-car-miles, or ton-miles. In recent years, the energy intensity of trucking and rail has remained relatively stable.
Air quality is affected by freight vehicle emissions. Compared with gasoline-fueled cars and trucks, diesel-fueled heavy trucks emit small amounts of carbon monoxide (CO) but larger amounts of nitrogen oxides (NOx). However, since 2000 the rate of NOx emissions from diesel-fueled heavy-duty trucks declined by 69.6 percent.
The U.S. Environmental Protection Agency (EPA) estimates that trucks produced more than 2.3 million tons of NOx in 2016. Substantial reductions in freight-related NOx emissions have been made since the EPA required the use of ultra-low sulfur diesel fuel in heavy-duty trucks and other diesel-powered highway vehicles beginning in 2006. Between 2000 and 2016, NOx emissions from gasoline- and diesel-powered single-unit and combination trucks decreased by 63.4 percent. PM-10 emissions declined by 59.3 percent over the same period. By 2030 truck-related NOx and PM-10 emissions are projected to decline by 84.6 percent and 78.1 percent, respectively, from 2000 levels.
In addition to carbon monoxide, nitrogen oxide, and particulate matter emissions, the transportation sector releases large quantities of greenhouse gases (GHGs), such as carbon dioxide, methane, nitrous oxide, and hydrofluorocarbons. Transportation was responsible for about 27.5 percent of all greenhouse gases emitted in the United States in 2015, second only to the industrial sector which produces the largest amount of GHG emissions (29.3 percent).
Carbon dioxide (CO2 ) accounts for nearly all of the transportation sector’s greenhouse gas emissions, primarily from the combustion of fossil fuels. Almost all of the energy consumed by the sector is petroleum-based and includes motor gasoline, diesel fuel, jet fuel, and residual oil. Gasoline-fueled passenger cars and light-duty trucks are responsible for about 63.1 percent of transportation sector CO2 emissions, while the combustion of diesel fuel in medium- and heavy-duty trucks and jet fuel in aircraft produced much of the rest.
Although CO2 emissions from the transportation sector have leveled off in recent years, they were 8.0 percent lower in 2015 than in 2005. However, the transportation sectors share of total U.S. CO2 emissions increased slightly to 34.4 percent in 2015, likely the result of more travel, population and economic growth, and/or low fuel prices.
Since 2005 greenhouse gas emissions from both freight and passenger transportation sources have declined. Passenger emissions declined at a faster rate at 13.5 percent than that of freight. Between 2005 and 2015, truck emissions rose by 4.0 percent and pipeline by 17.3 percent. An increase in the volume of freight movements by truck and pipeline contributes to the rise in their emissions over the last two decades.
Water quality is affected by oil spills from vessels and pipelines transporting crude oil and petroleum products and by facilities, such as offshore drilling units and platforms. In 2016 vessel-related spills accounted for 79.1 percent of total gallons spilled. Since 2000, significant reductions were seen in the number of oil-spill incidents and in the total gallons of oil spilled, 68 and 79 percent, respectively.