§ Mr. Austin Mitchell
To ask the Secretary of State for Transport what allowance was made in calculation of the costs of maintenance of the rail structure by W. S. Atkins for the backlog of inspections on maintenance left undone by British Rail. 
§ Mr. Watts
Railtrack's asset maintenance plan for track and route structures, prepared with the assistance of W. S. Atkins, forecasts the expenditure considered to be necessary to sustain the operating capability of the relevant assets in accordance with Railtrack's operational policies and standards.
§ Mr. Mitchell
To ask the Secretary of State for Transport (1) if he will make a statement on the relevance of Bayesian probability theory to the maintenance costs of the rail structures, with particular reference to the allowance made in such analyses for the age of the asset and its condition; and what assessment he has made of the comparative value of(a) Bayesian analysis of cost estimates and (b) estimates based on inspection of the assets; 
(2) what the estimated costs of maintenance of the rail structure were in the W. S. Atkin's report before and after refining by Bayesian probability theory. 
§ Mr. Watts
Bayesian probability theory is an established modelling technique relevant to determining estimates of maintenance expenditure for rail and other structures. Independent expert consultants, W. S. Atkins, employed by railtrack to assist in the development of its asset maintenance plan—AMP—for track and route structures, used Bayesian statistical techniques in its analysis of data on the condition of certain assets, gained from sample surveys. The estimates in the Atkins report were derived from Bayesian analysis throughout for those assets to which it was applied.