The collection of the data that lies behind these publications is a complex and time-consuming process.
The financial database
At the heart of the project lies a major database, produced to a common format, and containing data on all the major bus companies since 1992, on the major train and freight operating companies since their incorporation in the late 1990s and on most of the light rail and rapid transit schemes in the UK since their opening.
The database contains three main files - results, costs and revenue - with each figure recorded by the companies in their accounts codified into a set of common categories and then entered into the system. As a result, we believe that a key element is maintaining a consistency of approach - both across the years and between companies - and in trying to ensure that where there are differences (for example through exceptional or extraordinary items or a change in financial reporting standards) these are noted and explained.
We cannot of course guarantee complete commonality of data, because different companies adopt slightly different reporting standards, and offer different levels of detail in their accounts. But at a given level we believe that the analysis is as consistent and as reliable as it possibly can be given the available data.
In addition to the three central files - all linked by a system of strict refential integrity - there are a number of subsidiary files covering other aspects of the database - the fleet analysis, for example, or patronage and revenue data (where this is available for individual companies, as it usually is for the rail and light rail indiustries).
Even where we adapt our data collection to match changing circumstances - tracking pension costs, for example, or noting the nature and extent of pension scheme liabilities, we try to do this within the overall structure.
A second major source of information comes in the form of Government statistics - published by the Department for Transport, by the devolved governments in Scotland, Wales and Northern Ireland, by industry bodies (such as the Office of Rail Regulation), and by local and sub-regional governments and transport executives. We do not aim not to reproduce these figures slavishly - there's no point, since they're freely and widely available on the internet. But what we do try to do is to pick up on the most relevant and the most interesting - and to bring together common topics from different publications (Transport Statistics Great Britain and the National Travel Survey from DfT for example, and National Rail Trends from the ORR or TfL's annual statistical reports.