When a delay analysis is performed years after the events in question — typically in the context of arbitration — the SCL Delay and Disruption Protocol recognises that a different methodological approach may be appropriate compared with contemporaneous analysis. Core Principle 11 introduces six recognised methods of delay analysis, each with its own evidential demands and analytical strengths.
The six methods are: impacted as-planned, time impact analysis, time slice windows, as-planned versus as-built windows, longest path, and collapsed as-built (also known as 'as-built but for'). Each method approaches the question of cause and effect differently, and each is suited to particular circumstances.
Impacted as-planned is the simplest method: a fragnet representing the delay event is inserted into the as-planned baseline programme, and the resulting impact on the planned completion date is measured. This method is quick and cheap, but takes no account of actual progress and is often criticised as theoretical.
Time impact analysis (TIA) is a prospective method that inserts the fragnet into the most recent updated programme prior to the delay event. It is the SCL Protocol's preferred method for contemporaneous analysis, and is widely accepted by tribunals in the Middle East.
Time slice windows analysis uses a series of contemporaneous programme updates to track the development of the critical path through the project, attributing delay at each window to identified causes. As-planned versus as-built windows analysis compares planned and actual progress within defined time windows. Both methods are evidence-intensive and require good contemporaneous programmes.
Longest path analysis identifies the as-built longest path through the works and traces the causes of delay along that path. Collapsed as-built analysis starts from the as-built programme and removes the effects of identified delay events to determine what completion date would have been achieved 'but for' those events.
The choice of method is one of the most important decisions a delay expert witness makes, and is heavily influenced by the available records, the contractual framework and the nature of the dispute. The Protocol stresses that no single method is universally correct, and that the expert should select the method best suited to the case and explain that choice transparently.