The physical extent of the Nation’s transportation infrastructure has changed little in two decades. Public road and street mileage increased nearly three-tenths of a percent per year while vehicle-miles of travel grew 1.3 percent per year between 1993 and 2013; the total number of airports, including general aviation facilities, increased three-tenths of a percent per year, while the number of public use airports declined; the mileage of navigable waterways remained unchanged; and the mileage of class I railroads shrank 1 percent per year from 1991 to 2011.

Each edition of the Transportation Statistics Annual Report has tracked incremental changes in fleets operating on the transportation system, capacity of the system, and delay caused by congestion. Some of the changes in the transportation system not anticipated in the 1994 edition involve aviation and maritime connections between the United States and the rest of the world.

The number of U.S. airports with nonstop international service increased from 72 in 1993 to 89 in 2013, offering more locations throughout the country with commercial air service to the world [USDOT BTS 2015]. While 14 airports lost international service, 31 airports gained international service in that time. The number of air passengers traveling between the United States and foreign points reached a new high in 2010 and has increased each succeeding year.

Maritime connections with the world involve increasingly larger vessels. Containerships calling in the United States had an average capacity of 3,903 twenty-foot equivalent units (TEUs) in 2012, up 28.9 percent from 2002 [USDOT MARAD 2014]. The newest container ships carry upwards of 18,000 TEUs of cargo [ABS 2014], and even larger containerships are on order. This increase in size is not limited to container ships. Today’s largest cruise ships are more than 225,000 gross tons and carry nearly 6,400 passengers and 2,400 crew [RCL 2014]. By comparison, the Titanic was about 46,000 gross tons and carried 1,300 passengers and 900 crew (see figure 11) [CP 2012].

The 1994 Transportation Statistics Annual Report did not anticipate two major changes in the maritime transportation network, both of which are beyond U.S. territorial waters. One is the expansion of the Panama Canal with a third set of locks that will allow post-Panamax vessels up to 13,000 TEUs to transit the canal (see figure 12). Because the United States accounts for 69.2 percent of the total tonnage passing through the canal, this expansion could affect the share of international traffic flowing to and from the coasts described previously [PCA 2014]. The other change is a consequence of climate change. The current Arctic maritime season lasts from about June through October, with unaided navigation (without icebreaking, etc.) occurring within an even more limited time frame. If shrinkage of the Arctic ice cap continues, an extended maritime season may make the once fabled Northwest Passage a commercial reality. For many major port cities, the Northwest Passage through the Arctic Ocean may seasonally offer shorter routes than those that traverse the Panama and Suez Canals [CMTS 2015].

Perhaps the biggest pending change in the transportation system not anticipated in 1994 is the rapid development of autonomous, or selfdriven, vehicles. Long considered in the realm of science fiction and futurists, a handful of experimental automobiles and trucks are in actual operation on public streets. The rate of adoption and the consequences of automated vehicles for vehicle-miles of travel, safety, freight economics, and mobility for the aging population are all subject to speculation and are yet to be measured.

In addition to driverless trucks, automation in the freight system includes package handling in warehouses operating today and the possibility of parcel delivery by unmanned aerial vehicles in the near future. These changes could have significant consequences for transportation costs and employment.