In undertaking economic appraisals of black spot projects such as those at small intersections, impacts on road user costs, e.g. traffic impacts, are usually excluded from the analysis with the focus on crash costs. Exclusion of traffic impact costs and benefits is understandable given the detailed data and complex modelling required. Detailed evaluation of the traffic impacts of intersection treatments, i.e. signed intersections, roundabouts and signalised intersections, is usually undertaken with intersection analysis software specially developed for the purpose. The objective of this project is the development of an economic evaluation tool for small intersection projects (involving signed intersections, roundabouts and signalised intersections) that can be used by practitioners working with basic traffic data to estimate traffic impacts, primarily delay and fuel cost savings, as well as crash cost savings arising from intersection treatments. The aim is therefore not to replicate sophisticated intersection analysis software developed to undertake detailed analysis of large intersection projects. Rather, the objective is to facilitate the rapid economic evaluation of a number of small intersection projects which could provide an indication of the most promising projects which can then be subject to further detailed traffic impact analysis thereafter. Given these objectives and rationale, the Tool was therefore given the title of Small Intersection Evaluation (SIE) Tool. In compiling the SIE Tool, the study involved a review of material and approaches involving the estimation of traffic impacts and crash costs. This included an aaSIDRA evaluation of traffic impacts at black spot intersection projects undertaken by John Piper Ltd for the Bureau of Infrastructure Transport and Regional Economics (BITRE), as well as intersection evaluation approaches and tools developed by jurisdictions, e.g. the CARP model developed by Queensland Department of Transport and Main Roads (TMR) and ISEVAL developed by VicRoads. The development of the SIE Tool is then set out in detail, including its overall design, methodology and data requirements (base case and project case) for the estimation of traffic impacts at signed intersections, roundabouts and signalised intersections. The estimation of crash costs across intersection types is also presented, including appropriate crash rates and crash modification factors (CMFs) incorporated into the SIE Tool. Results of the intersection evaluation in terms of economic decision rules, i.e. net present value (NPV) and benefit cost ratio (BCR) are provided. The report also sets out the process used to review and test the SIE Tool against available case studies. This includes feedback received from jurisdictions on testing the tool and the appropriate adjustments made to the tool in response to the comments. Finally, it must be noted that the coefficients used to estimate delay and vehicle operating costs in the SIE Tool are updated periodically via a separate, off-line process as new unit values (e.g. travel time and fuel costs) become available. The SIE Tool and a User Guide is provided separately and can be downloaded from the Austroads publications website. (Author/publisher)
Abstract