Combined use of a backcast scenario and cross-impact matrix analysis to identify causes of uncertainty in a nascent transport infrastructure project

The transport planning decision process is, in theory, underpinned by rational analysis of travel behaviour and application of transport economics but project outcomes do not always follow the results of that analysis. Uncertainty is evident at all stages of the project development, as the concept emerges and as it moves through the subsequent assessment and decision processes. This research has investigated and demonstrated a method that quantifies the factors contributing to uncertainty, focussing on the early stages of the project lifecycle. The method used a back-cast scenario to describe a future view of a transport project. The causal relationships between elements of the planning and decision processes that led to the scenarios were discussed in structured interviews with stakeholders, and each conversation was coded using qualitative analysis techniques to identify the active elements of the process. Causality between the elements was explored to evaluate their influences and dependencies with those elements found to be simultaneously both highly influential and highly dependent were identified as those driving uncertainty. The sensitivity of the analytical element of this process to its parameters was also examined to quantify their contribution to the uncertainty in the analysis and to establish robust values for these parameters. The specific scenario presented here was based on a disused railway where several studies evaluating its re-opening have resulted in contradictory views on its mode of use and on the achievable benefits. In the scenario, the rail service is re-instated for light rail use in conjunction with a new sustainable urban area anchored on an existing small village. In this case, the results showed that local politics and leadership were the most influential factors in the project while the economic environment, the utility of the proposal, and planning policy contributed most to the uncertainties in the project. Although these results emerged from a specific scenario, the methodology was demonstrated to be a powerful generic tool to identify the elements that create criticalities in the planning and decision process. Therefore, the integrated method has application in other areas of project inception and planning, much wider than in the transport application demonstrated here.