Organisation for Economic Co-operation and Development

Although there are clear definitions for all the terms used in this survey, countries might have different methodologies to calculate tonne-kilometre and passenger-kilometres. Methods could be based on traffic or mobility surveys, use very different sampling methods and estimating techniques which could affect the comparability of their statistics. Also, if the definition on road fatalities is very clear and well applied by most countries, this is not the case for road injuries. Indeed, not only countries might have different definitions but the important underreporting of road injuries in most countries can distort analysis based on these data. 

Data are collected from Ministries of Transport, national statistical offices and other institutions designated as the official data source. The survey used for this exercise is the "Investment Spending in Transport Infrastructure". The original data is collected in national currency, current values. Data are converted and published in euros, both current and constant (2015 prices). The variables collected include investment, maintenance spending and capital value of road, rail, inland waterways, maritime ports and airports. Data are published annually on 31 March. Data series start in 1995 and continue until the current year-2, or the most recent available data.