A New Approach to Feasibility Risk Assessment within Transport Infrastructure Appraisal

AbstractThis paper introduces a new approach of applying feasibility risk assessment within transport project infrastructure appraisal. The procedure is based upon quantitative risk analysis and Monte Carlo simulation in combination with conventional cost-benefit analysis converting deterministic benefit-cost ratios (BCRs) into stochastic interval results. Recent research has proven that particularly input based impacts such as construction cost and demand forecasts (travel time savings) often are respectively underestimated and overestimated creating so-called Optimism Bias. Decision-makers and stakeholders are, hereby, often basing their decisions on wrongful material. The presented approach to transport infrastructure appraisal is to include uncertainties and risks in the evaluation. Correspondingly, the handling of uncertainties and risk within transport project assessment are often made up by sensitivity tests producing deterministically based output values. Research has proven that traditional sensitivity analysis seldomnly captures the total variability especially as concerns the costs and demands estimated in the pre-stage of the evaluation. Therefore, this paper introduces an approach to decision support based upon so-called reference class forecasting using historical information from similar past projects. The scheme is made evident through a brand new database sample (UPD: the UNITE Project Database) which contains almost 200 specific European transport infrastructure projects. Hence, the approach will be tested and further explored upon a fixed case example depicting a new fixed link between Elsinore (Denmark) and Helsingborg (Sweden) revealing a severe decrease in economical return including relevant UPD information. Finally, a conclusion and perspective of the further work will be discussed

Integrating Life-cycle Assessment into Transport Cost-benefit Analysis

AbstractTraditional transport Cost-Benefit Analysis (CBA) commonly ignores the indirect environmental impacts of an infrastructure project deriving from the overall life-cycle of the different project components. Such indirect impacts are instead of key importance in order to assess the long-term sustainability of a transport infrastructure project. In the present study we suggest to overcome this limit by combining a conventional life-cycle assessment approach with standard transport cost-benefit analysis. The suggested methodology is tested upon a case study project related to the construction of a new fixed link across the Roskilde fjord in Frederikssund (Denmark). The results are then compared with those from a standard CBA framework. The analysis shows that indirect environmental impacts represent a relevant share of the estimated costs of the project, clearly affecting the final project evaluation. Additionally, they can significantly modify the weight of the different components of the overall project costs – evidently becoming a significant part of the estimated construction cost. Therefore, the suggested approach guarantees a higher quality of information thus providing decision makers with a more thorough insight of the environmental impact of the project

Transport assessment and risk analysis: the case of the 2nd fixed link across the Danube River

The scope of this paper is to present a new methodology for appraising transport infrastructure projects. Conventionally, transport infrastructure appraisal is conducted by the use of cost-benefit analyses (CBA) in order to produce aggregated single point estimates. However, new research has proved that the embedded uncertainties within traditional CBA such as ex-ante based investment costs and travel time savings are of high significance. This paper investigates the latter two impacts in terms of the Optimism Bias principle which is used to take account of the underestimation of construction costs and the overestimation of travel time savings. By extending this principle into stochastic modelling where a quantitative risk analysis (QRA) is applied, so-called feasibility risk assessment is provided by moving from point (deterministic CBA) to interval (stochastic QRA) results. Hereby, decision support as illustrated in this paper will aim to provide assistance in the development and ultimately the choice of action, while accounting for the uncertainties surrounding transport appraisal schemes. Evidently, the methodological approach is illustrated by a case example from the Northern region of Bulgaria

Modelling of Transport Project Uncertainties: Feasibility Risk Assessment and Scenario Analysis

This paper proposes a new way of handling the uncertainties present in transport decision making based on infrastructure appraisals. The paper suggests to combine the principle of Optimism Bias, which depicts the historical tendency of overestimating transport related benefits and underestimating investment costs, with a quantitative risk analysis based on Monte Carlo simulation and to make use of a set of exploratory scenarios. The analysis is carried out by using the CBA-DK model representing the Danish standard approach to socio-economic cost-benefit analysis. Specifically, the paper proposes to supplement Optimism Bias and the associated Reference Class Forecasting (RCF) technique with a new technique that makes use of a scenariogrid. We tentatively introduce and refer to this as Reference Scenario Forecasting (RSF). The final RSF output from the CBA-DK model consists of a set of scenario-based graphs which functions as risk-related decision support for the appraised transport infrastructure project. The presentation of RSF is demonstrated by using an appraisal case concerning a new airfield in the capital of Greenland, Nuuk

Optimering af Hastighedsprofilet ved opgradering af Jernbaner

Gennem bl. a. Togfonden DK er der bevilget penge til en lang række jernbaneopgraderinger over hele landet. Der ligger derfor et stort projekteringsarbejde foran sektoren, hvilket bl.a. øger behovet for optimering af arbejdsprocesserne. Når sporets horisontale geometri, som grundlæggende består af kurver og rette linjestykker, forberedes til hastighedsopgradering, er det billigste tiltag at øge kurvernes overhøjde. Dette skal dog ske under hensyntagen til de krav og regler, Banedanmark har fastsat, og som sikrer et minimum af slid af infrastrukturen samt en sikker og komfortabel rejse for passagerne. I dag er der et stort manuelt arbejde forbundet med at vurdere muligheden for øge kurvernes overhøjde for at opnå en højere hastighed. Opgaven kompliceres yderligere af, at kurver, der deler en overgangskurve, påvirker hinanden indbyrdes – overhøjden, der vælges i den første kurve, har betydning for, hvilken overhøjde der kan vælges i den næste kurve og så fremdeles. Ydermere gælder der forskellige krav, alt efter om der projekteres efter ønskelige, normal- eller undtagelsesbestemmelser, ligesom perroner og sporskifter pålægger andre begrænsninger. Det er derfor vanskeligt og tidskrævende at finde det optimale hastighedsprofil manuelt. Denne artikel præsenterer en ny optimeringsmodel, som giver en løsning langt hurtigere og med garanti for optimalitet ud fra de givne forudsætninger. Modellen testes på en given strækning hvor kurveradier, kurvelængder, længden af overgangskurver og stationeringer benyttes som input. Ligeledes indikeres det på forhånd, i hvilke kurver der findes sporskifter og perroner, samt hvilke kurver, der ønskes projekteret efter hhv. ønskelige, normal- og undtagelsesbestemmelser. De krav og normer, der skal efterleves, indsættes som begrænsninger til modellen, således at de i løsningen vil være overholdt. Modellen optimerer overhøjder efter at finde den højest mulige hastighed i kurverne, således at hastighedsprofilet på strækningen bliver optimalt. Ud fra resultaterne fra modellen kan de kurver, der er begrænsende for hastigheden, hurtigt identificeres. Der kan herefter tages stilling til, om der for at opnå højere hastighed i disse kurver skal tillades undtagelsesbestemmelser, om overgangskurven skal forlænges eller om der skal foretages en kurveudretning. I forhold til en manuel proces kan der derfor identificeres en række forskellige scenarier for, hvordan en given banestrækning kan hastighedsopgraderes, således at beslutningsgrundlaget i sidste ende kan forbedres