Transportation is supplied by individual firms of all sizes and by government agencies. The range of government involvement differs by type, or mode, of transportation and the geographic or political areas of jurisdiction. Governments are involved in providing transportation because it is necessary for economic development, for carrying out certain other functions of government (such as public safety or making it easier for individuals to reach schools or hospitals), and for national defense.

In the United States, airlines are run as private firms, while airports and the air traffic control network are supplied by government. Motorists and trucks operate in the private sector and travel on highways provided by the public, largely through taxes collected on motor fuels. Barges and Great Lakes carriers and oceangoing ships are private-enterprise operations, paying low levels of user fees. They travel on waterways improved and maintained by governments. Railroads are private-enterprise ventures operating on their own roadbed and track. An exception is intercity rail passenger service, which is provided by a government agency. Oil and gas pipelines are operated by private enterprise. Mass transit operations carrying large numbers of passengers in urban areas on buses, light rail vehicles, and ferries are usually operated in the public sector. At one time mass transit was provided by the private sector, but private firms could not survive much beyond World War II, when automobiles became popular. Communities, later aided by the federal government, bought out the declining private transit operators and replaced them with public-enterprise operations. Vehicles, aircraft, and ships are usually built by firms in the private sector.

Outside the United States, public ownership and operation of transportation is quite common. Most nations own and operate their railroads and airlines. Automobiles and trucks are built in the private sector, but roads are provided by the public. Ships may be either publicly or privately owned, although virtually all nations subsidize their merchant marine.

So, in the supply of transportation services, a mix of public and private entities is usual. Private firms are responsive in situations where there is a profit to be made. If the market will not support profitable operators, a variety of government subsidization schemes are used. Ideal schemes allow the subsidized operator to develop business to a point at which the subsidies are no longer needed. Frequently this does not happen; the users—or the employees—of the carrier enjoy the subsidies and assert political pressure on governments to maintain them. Governments are confronted by groups who demand certain levels of transportation service but are unable, or unwilling, to pay for them. Subsidized carriers then pursue objectives that may differ from the aims of economic efficiency. This leads to a redistribution of income from the general taxpayer to the user of the subsidized transportation operation. Subsidized transportation also affects decisions made by firms determining where to locate plants or by individuals determining where to locate homes. Both groups in making these decisions attempt to minimize transportation costs that they must pay. If the costs these groups must pay are not the same as the true and total costs to society, the low-transportation-cost site in their eyes is perhaps not the same as might be chosen by one knowing—or having to pay—all transportation costs.

A form of investment analysis for long-range government investments is benefit-cost or benefit-to-cost analysis. It is more widely used for transportation undertakings than for other public-sector investments. Long-term projections of benefits and costs are made. These future flows are then discounted, through use of a rate of interest, back to the present value. (For example, using a 5 percent compound interest rate, $1,000 10 years in the future is worth $614 today.) Costs of a project include land—such as that needed for the right-of-way—site preparation and construction of the facility. Future operating costs of the facility also must be considered.

Benefits are usually savings in travel time for passenger-oriented projects and savings in transportation costs for freight. An example of this would be dredging a harbour. If the plans would permit a larger vessel to be used, the costs per ton for shipping would be lowered, and this would be considered a benefit. Benefit-cost analysis can be applied to a variety of projects and, if similar assumptions are used in performing the analysis for each, then the projects can be ranked in the order that should be used for getting the greatest return for the governmental investment.

In the United States, so much transportation is conducted with private automobiles that passenger transport could almost be equated with automobile transport. The most common trip is the journey to work, a to-and-fro movement 5 days each week, 50 weeks per year. The individual concerned may have chosen both a job and a home while thinking of the daily journey that would have to be conducted between the two. In the United States, the vast majority of journeys to and from work take place in private automobiles, often with the driver alone, carrying no passengers. Car pools are encouraged in most large urban areas by setting aside certain lanes on freeways in and out of the city for use by vehicles carrying multiple passengers. On toll roads and bridges, and at freeway entrance points, they may also receive preference.

There is also work-related travel, which may be conducted in any sort of vehicle. The demand for such a trip must outweigh both the transportation costs and value of the individual’s time spent while traveling. Some individuals travel in search of work. There also are migrations of people from one part of the country to another, seeking a job and a better life. There have been, and will continue to be, large migrations throughout the world.

Travel to and from school is a regular movement for many people. Buses may be provided by the school district, or public transportation may be used. Individuals also need transportation for shopping, visits to doctors, visits to friends, and other personal reasons. Some persons travel for religious purposes on pilgrimages to sites of special significance. Vacation and pleasure travel form another demand for transportation services.

Individual demands for transportation can be aggregated into demands for larger vehicles. Examples are commuter trains that operate near large cities or aircraft that fly coast-to-coast or across the ocean. Most passengers have several alternative modes of transportation or carriers from which to choose. A commuter may drive alone, be part of a car pool or a vanpool, or ride on a bus, ferry, or train. Part of the person’s decision as to type and size of vehicle is based on the value of his or her time and the relative comfort and convenience associated with travel in each vehicle type.

Demand for freight transportation is generally a function of demand for a product. A simple definition of demand for freight transportation is that it reflects the difference between a commodity’s value in two different markets. If oranges are worth $4 a bushel in Florida and $10 a bushel in Chicago, then the demand for transporting oranges from Florida to Chicago is expressed as $6 a bushel. As oranges begin moving from Florida to Chicago, the spread in market prices will start to decrease and will eventually drop to the point where it no longer covers the costs of transportation.

Freight is time-sensitive. Fresh seafood is perishable; newspapers must be delivered promptly. Shippers have money invested in inventory and often want to use faster modes of transportation to reduce the amount of time they must wait for payment.

For some goods, the cost of transportation is nearly the same as the cost of the product, and it thus influences demand for both the product and its carriage. Steel-mill slag (a by-product of the steel-making process) has almost no market value, and sometimes steel mills must pay to have it carried away. It can be used as an aggregate in concrete but competes with other materials, such as sand, which are very low in cost. Many recycled products also have almost no market value, and transportation costs become the major factor viewed by those who may want to buy the recycled products for some subsequent use.