Legacy Book

You are here

Chapter 3 The Freight Transportation System

Freight travels over an extensive network of highways, railroads, waterways, pipelines, and airways.  Existing and anticipated increases in the number of freight vehicles, vessels, and other conveyances on both public and private infrastructure are stressing the system as more segments of the network approach or reach capacity, increasing maintenance requirements, and affecting performance.


Road infrastructure increased slightly despite a 28.2 percent increase in population over the 1990 to 2013 period (see table 1-1). The number of Class 1 rail miles declined by 28.6 percent while gas pipeline mileage increased by 24.0 percent over the same period.

Table 3-1. Miles of Infrastructure by Transportation Mode:  1990, 2000, and 2010-2013

Table 3-2. Freight Intermodal Connectors on the National Highway System by State:  2014

Intermodal connectors provide access between major intermodal facilities, such as ports and truck/pipeline terminals, and the National Highway System (NHS). Although intermodal connectors account for about one-half of one percent of total NHS mileage (1,222 miles), they handle a large volume of trucks.

Figure 3-1. National Network for Conventional Combination Trucks: 2014

The National Network was established by Congress in 1982 to facilitate interstate commerce and encourage regional and national economic growth by requiring states to allow conventional combination trucks on the Interstate System and portions of the Federal-aid Primary System   of highways. The National Network, which is approximately 180,000 miles in length, has not changed significantly in three decades.

Figure 3-2. Permitted Longer Combination Vehicles on the National Highway System: 2014

Longer combination vehicles (LCVs) include truck tractors pulling a long semi-trailer and a short trailer (often called a Rocky Mountain Double), a long semi-trailer and a long trailer (often called a Turnpike Double) or a short semi-trailer and two trailers (called a Triple).  Although all states allow conventional combinations consisting of a 28-foot semitrailer and a 28-foot trailer, only 14 states and 6 state turnpike authorities allow LCVs on at least some parts of their road networks.  Allowable routes for LCVs have been frozen since 1991.

Table 3-3. Number of Trucks, Locomotives, Rail Cars, and Vessels: 1990, 2000, and 2010-2013

Nearly 12 million trucks, locomotives, rail cars, and vessels move goods over the transportation network. The number of highway vehicles and vessels has remained relatively stable in recent years, while the number of rail cars has continued to decline with improved utilization and the deployment of larger cars.

Table 3-4. Condition of U.S. Roadways by Functional System:  2000, 2005, and 2011-2013


The U.S. Department of Transportation, Federal Highway Administration uses the International Roughness Index to measure the smoothness of pavement. In urban areas, interstates and other expressways and principal arterials showed large improvements in pavement smoothness in the 2000 to 2013 period. In rural areas, major collectors showed the greatest improvement (10.7 percent) in pavement smoothness while other principal arterials had the greatest increase (24.0 percent) in road roughness. Rural interstates and minor arterials also had increases in road roughness.

Figure 3-3. Condition of U.S. Bridges by Age Group: 2013

The overall condition of bridges has improved slowly over time. In 2000, 15.2 percent (89,415) of bridges were considered structurally deficient compared to 10.5 percent (63,521) in 2013. Structurally deficient bridges are characterized by the deteriorated condition of bridge elements and reduced load-bearing capacity. In some cases, weight restrictions are placed on structurally deficient bridges, which may impact freight movement.

Table 3-5. Class I Railroad Locomotive Fleet by Year Built:  2000, 2010, and 2013

The median age of the Class I Railroad locomotive fleet ranged from 9 to 13 years in 2013, compared to 16 to 20 years in 2000. Class I railroaded added 9,788 new locomotives between 2000 and 2013. On average, about three percent of all locomotives are new in any given year.

Table 3-6. Automated Track Inspection Program Exceptions per 100 Miles: 2007-2014

The U.S. freight rail system owns and operates more than 138,000 rail miles, including 95,000 miles owned by Class I railroads (those having revenues of at least $467.1 million in 2013). The remaining mileage is owned and operated by regional and local railroads. Of the eight track characteristics monitored, the incidence of two—gage and limited speeds—are lower since 2010, while other results are more varied.

Table 3-7. U.S. Flag Vessels by Type and Age:  2000, 2010, and 2013

U.S. flag vessels operate on both shallow and deep draft waterways and include a wide range of vessel types. The age of the fleet decreased over the 2000 to 2013 period: vessels age 15 years and younger decreased from 46.0 percent to 33.9 percent. Inland waterway barges accounted for the largest share (77.7 percent) of U.S. vessels. Towboats are the oldest vessels in the fleet with 68.9 percent older than 25 years. In contrast, barges are among the youngest vessels due to a combination of retirement and replacement of older dry cargo barges and acquisition of new tank barges.

Table 3-8. Lock Characteristics and Delays in Rivers with 5,000 or More Lockages:  2000, 2010, and 2014

Locks make it easier for vessels to navigate the uneven water levels of U.S. rivers. Because of increasing traffic and aging locks, vessels may be delayed for hours while locks are shut down for maintenance and repair. The U.S. Army Corps of Engineers reports that the average age of all locks in 2014 was 59 years. Between 2000 and 2014, average delay per lockage nearly doubled from 64 minutes to 121 minutes. In 2014 the highest average lockage delay was on the Tennessee River at 277 minutes, while the Gulf Intracoastal Waterway had the highest percent of vessels delayed at 90.

Freight Flows

Trucks carry most of the tonnage and value of freight in the United States, but railroads and waterways carry significant volumes over long distances.  Rail moves a large volume of coal between the Powder River Basin in Wyoming and the Midwest, while the principal inland waterways movement, by freight volume, occurs along the Lower Mississippi River.

Figure 3-4. Freight Flows by Highway, Railroad, and Waterway: 2011

Figure 3-5. Average Daily Long-Haul Truck Traffic on the National Highway System:  2011

Long-haul freight truck traffic in the United States is concentrated on major routes connecting population centers, ports, border crossings, and other major hubs of activity.  Except for Route 99 in California and a few toll roads and border connections, most of the heaviest traveled routes are on the Interstate System.

Figure 3-6. Average Daily Long-Haul Truck Traffic on the National Highway System:  2040

By 2040 long-haul freight truck traffic in the United States is expected to increase dramatically on the National Highway System.

Figure 3-7.  Major Truck Routes on the National Highway System:  2011

Several routes carry a significant concentration of trucks, either as an absolute number or as a percentage of the traffic stream. In 2011 nearly 14,530 miles of the NHS carry more than 8,500 trucks per day on sections where at least every fourth vehicle was a truck.  With each truck carrying an average of 16 tons of cargo, 8,500 trucks per day haul approximately 50 million tons per year.

Figure 3-8.  Major Truck Routes on the National Highway System:  2040

The number of NHS miles carrying large volumes and high percentages of trucks is forecast to increase dramatically by 2040.  Segments with more than 8,500 trucks per day and where at least every fourth vehicle is a truck are forecast to reach 42,000 miles, an increase of more than 175 percent from 2011.

Table 3-9. Annual Vehicle Distance Traveled by Highway Category and Vehicle Type:  2013

Freight moving in combination trucks depends heavily on the Interstate System. While less than one-fourth of the distance traveled by light-duty vehicles is on the Interstate System, over one- half of combination-truck vehicle-miles of travel are on Interstate highways.

Figure 3-9. Share of Highway Vehicle-Miles Traveled by Vehicle Type:  2013

Despite doubling over the past two decades, truck traffic remains a relatively small share of highway traffic as a whole. In 2013 commercial trucks accounted for approximately 9.1 percent of highway vehicle-miles traveled. Of that 9.1 percent, combination trucks accounted for approximately 61.2 percent, while single-unit trucks with six or more tires accounted for the remainder.

Table 3-10. Trucks, Truck Miles, and Average Distance by Range of Operations and Jurisdiction:  2002

Vehicle Inventory and Use Survey—in Retrospect

Tables 3-10 and 3-11 illustrate the data once provided by the Vehicle Inventory and Use Survey (VIUS), which was discontinued in 2002 due to budget constraints. VIUS had been the principal source of data on the physical and operating characteristics of the nation’s truck population. Based on a sample of registered trucks, VIUS was conducted as a mail-out-mail-back survey every 5  years from 1967 through 2002. The sample supported national and state-level estimates for freight carrying trucks and trucks used in other businesses and personal travel. Stakeholders across the federal government, state DOTs, Metropolitan Planning Office’s, and others who use VIUS estimates have had to rely on aging data since the survey was last conducted.

In 2014 the U.S. Department of Transportation formed a working group with the U.S. Department of Energy, U.S. Environmental Protection Agency, and U.S. Department of Agriculture to co-fund research on approaches to restore the survey. Advances in technology since 2002 have created opportunities to incorporate in-vehicle electronic data collection to augment traditional survey methods. New VIUS data would significantly improve the ability to estimate the number of trucks on the highway network, study future transportation growth, evaluate safety risks to highway travelers, and assess the energy efficiency and environmental impact of the Nation's truck fleet.

Table 3-11. Truck Miles by Products Carried: 2002

Federal and state governments are concerned about truck weight because of the damage that heavy trucks can do to roads and bridges. To monitor truck weight, more than 201 million weighs were made in 2013, about 65.8 percent of which were weigh-in-motion. Approximately 2.0 percent of commercial vehicle weighs discover violations. Despite the 2008–2012 drop in weigh- in-motion, 2013 has seen a slight increase over the 2007 level.

Table 3-12. Commercial Vehicle Weight Enforcement Activities: 2007-2013

Figure 3-10.  Tonnage of Trailer-on-Flatcar and Container-on-Flatcar Rail Intermodal Moves:  2013 

Different modes of transportation frequently work together to move high-value, time-sensitive cargo. The classic forms of rail intermodal transportation are trailer-on-flatcar and container-on-flatcar, and these services are spread throughout the United States.  The largest concentrations are on routes between Pacific Coast ports and Chicago, southern California and Texas, and Chicago and New York.

Table 3-13. Top 25 Airports by Landed Weight of All-Cargo Operations:  2000, 2010, and 2012-2014

The three most important U.S. airports that handle all-cargo aircraft are Memphis, Anchorage, and Louisville.  Memphis and Louisville are major hubs for FedEx and the United Parcel Service, respectively.  Anchorage is a major international gateway for trade with Asia. 

Figure 3-11. Top 25 Water Ports by Tonnage:  2013

Although the top ports for containerized cargo are primarily on the Pacific and Atlantic Coasts, most bulk cargo, such as coal, crude petroleum, and grain moves through ports on the Gulf Coast and inland waterway system. The top 25 water ports by tonnage handled 68.5 percent of the weight of all domestic and foreign goods moved by water. Port of Houston has the highest import trade at 76 million short tons, and Port of South Louisiana has the highest domestic tonnage movement at 127 million short tons.

Figure 3-12. Top 25 Water Ports by Containerized Cargo:  2014

Containerized cargo has grown rapidly in recent years and is concentrated at a few large water ports. The Ports of Los Angeles and Long Beach together handle 34.2 percent of all container traffic at water ports in the United States. Container trade at these two ports increased by nearly 68 percent between 2000 and 2014 while container trade for the entire United States grew by 77 percent.

Table 3-14. Containership Calls at U.S. Ports by Vessel Size and Number of Vessels:  2006-2011

Last reported by the USDOT Maritime Administration, from 2006 to 2011 the number of calls by containership with capacities of 5,000 TEUs or greater increased by 78.2 percent. These large container ships accounted for 27.0 percent of total containership calls at U.S. ports in 2011, up from 17.1 percent in 2006.

Table 3-15. Number of Vessel Calls at U.S. Ports:  2006-2011

In 2011, 7,836 oceangoing vessels made 68,036 calls at U.S. ports, a 13.5 percent increase from the previous year. Tankers accounted for 34.9 percent of total calls, followed by containerships (32.7 percent) and dry bulk vessels (16.0 percent). Approximately 98.0 percent of all tankers calling at U.S. ports are double-hull vessels, a 14.3 percent increase from 5 years earlier.

Table 3-16. Average Vessel Size per Call at U.S. Ports:  2006-2011

The average vessel size per call at U.S. ports increased from 50,653 deadweight tons (dwt)  in 2006 to 53,832 dwt in 2011, an increase of 6.3 percent. The average size of containerships increased by 13 percent in terms of TEU capacity (9.9 percent in terms of dwt) as carriers expanded the deployment of post-panamax container ships in U.S. trades. Post-Panamax refers to vessels that are larger than the width and length of the lock chambers in the Panama Canal.

Updated: Tuesday, June 27, 2017