Source Data

Freight

For an overall picture of freight transport between countries, trade data is a useful source. Trade data gives the tonnages and values of goods by their origin, destination and commodity type. Trade data does not often record mode of transport.

Countries publish their own trade data but the most useful sources at a regional level are the UN Statistics Division's COMTRADE database, which covers most countries in the world, and the Eurostat's Extrastat data for flows to and from the European Union.

Trade data is extremely useful but not perfect, some of the common problems are:

• Value is the main quantity recorded, tonnages may be incomplete or estimated
• Tonnages are the net tonnages of goods, the weight actually transported will be greater
• Origin and destination are usually the ultimate ends of the movement, but sometimes are intermediate transshipment points; flows to/from free zones may be excluded
• Very different sizes for a flow may be recorded by the two trading partners

Port data gives a more detailed picture of flows entering and leaving a country. This data gives tonnages transported and is usually broken down by handling type or commodity and direction. Classifications vary between countries, transit flows are often not clear. The recording of transshipment within a port also needs special attention.

Passengers

International passenger flows are available from various sources:

Air passengers are recorded by airports, usually broken down by arrival/departure and transit, international and domestic. National airport data usually includes routes, countries or regions of the world, this may come from airports, national airlines or air traffic data.

Sea passengers are usually recorded by ports, but often not by their origin/destination.

For land crossings, person counts are sometimes available but defintions are often not clear (for example, whether vehicle drivers are counted or not).

Immigration data is often a vital complementary source as it should be comprehensive. Usually it includes nationality and often, but not always, mode of transport. Tourism statistics can also be useful.

Some international sources are available, such as data assembled by Eurostat, airline databases such as IATA's and the World Tourism Organisation.