About the data
Definitions
Data sources
Transport infrastructure—highways, railways, ports and waterways, airports and air traffic control systems—and the services that flow from it are crucial to the activities of households, producers, and governments. Taken together, the services associated with the use of infrastructure (measured in terms of value added) account for 7–11 percent of GDP, with transport being the largest sector. Transport alone commonly absorbs 5–8 percent of total paid employment. Providing the infrastructure for transportation to meet the demands of a modern economy is one of the major challenges of economic development.
Internationally comparable data are not available for most transport subsectors. Unlike for demographic statistics, national income accounts, and international trade, the collection of infrastructure data has not been "internationalized." Even when data are available, they are often of limited value because of definitional incompatibilities, inappropriate geographical units of observation, or lack of timeliness. Serious efforts need to be made to create internationally comparable databases whose comparability and accuracy can be gradually improved. Because performance characteristics vary significantly by mode of transport and according to whether the focus is measuring the infrastructure or measuring the services flowing from the infrastructure, highly specialized and carefully specified indicators are required.
The table includes selected indicators of the size and extent of roads, railways, and air transport systems and the volume of freight and passengers carried. In addition to quantity, the quality of transport service is important in assessing an economy's transport infrastructure. The shipping sector (including port operations) is important for many economies, but internationally comparable data in this area are available for only a few countries and so are not presented here.
To measure the relative size of an indicator over time or across countries, some form of normalization is required. The table presents two normalized indicators: rail traffic per million dollars of GDP and the normalized road index. While the rail traffic indicator is normalized by a single indicator—the size of the economy—the normalized road index uses a multidimensional regression function to estimate the "normal," or expected, stock of roads in a country (Armington and Dikhanov 1996). The "normalizing" variables include population, population density, per capita income, urbanization, and regional differences. The value of the normalized road index shows whether the stock of roads in a country exceeds or falls short of the average for a country of similar characteristics.
• Paved roads are roads that have been sealed with asphalt or similar road-building materials.
• Normalized road index is the total length of roads in a country compared with the expected length of roads, where the expectation is conditioned on population, population density, per capita income, urbanization, and regional-specific dummy variables. A value of 100 is "normal." If the index is more than 100, the country's stock of roads exceeds the average.
• Goods transported by road are the volume of goods transported by road vehicles, measured in millions of metric tons times kilometers traveled.
• Rail traffic is the number of rail traffic units (the sum of passenger-kilometers and ton-kilometers) per million U.S. dollars of GDP.
• Goods transported by rail are the tonnage of goods transported times kilometers traveled.
• Aircraft departures are the number of domestic and international takeoffs of aircraft. • Passengers carried include both domestic and international aircraft passengers.
• Air freight is the sum of the tons of freight, express, and diplomatic bags carried on each flight stage (the operation of an aircraft from takeoff to its next landing) multiplied by the stage distance.
Data on roads are from the International Road Federation's World Road Statistics. The normalized road index is based on World Bank staff estimates. Railway data are from a database maintained by the World Bank's Transportation, Water, and Urban Development Department, Transport Division. Air transport data are from the International Civil Aviation Organization.
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