Developing the Riyadh strategic microsimulation model as a novel means of exploring policy transfer and future transport scenarios
Aldalbahi, Majid Mohammed
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Within just 50 years, Saudi Arabia's capital city Riyadh has developed from being a walled town to a modern metropolis of eight million people (ADA, 2015). Riyadh is a unique case study. Due to cultural and climate factors, there are good reasons why road transport dominates, with more than 93% of journeys undertaken by car. Despite substantial investment in the road network, there is severe traffic congestion caused by population growth and increased economic activity. This has made transport in and around the city time-consuming, unsafe, unhealthy and ultimately unsustainable. To address this, several high-profile projects are underway, most notably the Riyadh Metro, currently the world’s most expensive metro project, with a total value of 88 billion SAR. This research is therefore timely. It attempts to answer why Riyadh’s transport system has developed along its current lines, and whether schemes such as the Riyadh Metro will have the expected impact. To do this, the research had to operate from a strong multidisciplinary platform, linking transportation engineering, planning and urban studies to explore the issue of Policy Transfer as it applies to Riyadh. The Riyadh Metro is a paradigm case: it is a transport infrastructure that has proven successful in other (usually western) nations, and its application in Riyadh is expected to have similar benefits, despite the city’s cultural and climatic uniqueness. The research makes a substantial original contribution to knowledge by creating a strategic traffic microsimulation of Riyadh’s city core, using policy transfer insights, and unique access to Saudi Arabian stakeholder input, to develop a set of future scenarios which can be subject to a direct test in the model. This model has been created and calibrated using Riyadh traffic and mapping data, and professionally audited by the microsimulation company SIAS Ltd. One novel feature of the research is that this model is being used strategically. It enables four congestion indicators to be extracted under all network conditions, from free-flow conditions to complete saturation. These indicators are a) level of service, b) traffic flow, c) journey time and d) queue length. The values of the respective indicators will be logged and these, in turn, will represent coordinates for a so-called Overall Performance Curve (OPC). The various OPCs show how each of the indicators performs under all traffic conditions, enabling predictions about all possible future states to be explored. In other words, this research provides a scientific platform for future expectations. That’s where the policy transfer issues come in, by using the OPCs whatever the expectations, it will be on them somewhere, given that the OPC is like a formal scientific test-bed covering all scenarios and expectations. The first scenario to be explored (Scenario 1) is the ‘do nothing’ option. Current forecasts show the existing road network will be fully saturated by 2021, with a forecasted additional 40% traffic volumes in the study area. This will result in already lengthy journey times increasing by a further 90%, and queue lengths by 120%. Clearly, ‘doing nothing’ is not a viable option in light of population growth and economic development. Riyadh transportation authorities are already acutely aware of this. One further pioneering aspect of this research is its ability to survey key Riyadh stakeholders to discover what alternative scenarios are being pursued and considered, and to gauge their expected outcomes. Scenarios 2, 3 and 4 pick up on these expectations and subject them to a direct test in the strategic microsimulation model. As such, Scenario 2 embodies the current strategy involving the Riyadh Metro and examines the expected traffic reductions. According to the various OPCs, the Riyadh Metro will reduce the volume of cars on the road network by up to 43%. If these expectations arise in practice, journey times and queue lengths will be approximately halved compared with present conditions. The key, of course, is whether these expectations will in fact be met. In summary, this thesis makes a number of new contributions to theory. These include a mapping of the existing policy transfer theory to the situation pertaining to Riyadh, and an extension of existing theory to take account of unique socio-cultural and climatic factors. Solutions cannot be proven to be effective in any society unless they are tested and implemented. Thus, this research provides an opportunity for engineers, city planners, transport systems stakeholders/decision makers and beneficiaries to SEE the future in the present.