Vol 15 No 3 (2015)
2015-06-01
Vol 15 No 3 (2015)
2015-06-01
Articles
-
-
-
This note highlights how journal self-citation practices substantially influence impact factorbased journal rankings in the field of Transportation. Furthermore, by means of analyzing Thomson Reuters’ most recent Journal Citation Report (JCR), I show that a substantial share of these self-citations is likely to be the result of strategic behavior by editors of journals. I conclude with a call to editors to stop requesting or nudging authors to add journal self-citations to their papers; and a call to authors to stop giving in to editors when being asked to provide such citations.
This note highlights how journal self-citation practices substantially influence impact factorbased journal rankings in the field of Transportation. Furthermore, by means of analyzing Thomson Reuters’ most recent Journal Citation Report (JCR), I show that a substantial share of these self-citations is likely to be the result of strategic behavior by editors of journals. I conclude with a call to editors to stop requesting or nudging authors to add journal self-citations to their papers; and a call to authors to stop giving in to editors when being asked to provide such citations.
This note highlights how journal self-citation practices substantially influence impact factorbased journal rankings in the field of Transportation. Furthermore, by means of analyzing Thomson Reuters’ most recent Journal Citation Report (JCR), I show that a substantial share of these...
Caspar G. Chorus -
This following special issue of the European Journal of Transport Infrastructure Research (EJTIR) containing five scientific papers is the result of an open call for papers at the 1st International Conference on Uncertainties in Transport Project Evaluation that took place at the Technical University of Denmark, September 2013. The conference was held under the auspices of the project ‘Uncertainties in transport project evaluation’ (UNITE) which is a research project (2009-2014) financed by the Danish Strategic Research Agency. UNITE was coordinated by the Department of Transport of the Technical University of Denmark (DTU Transport) and carried out in cooperation with several Danish and international partners.
This following special issue of the European Journal of Transport Infrastructure Research (EJTIR) containing five scientific papers is the result of an open call for papers at the 1st International Conference on Uncertainties in Transport Project Evaluation that took place at the Technical University of Denmark, September 2013. The conference was held under the auspices of the project ‘Uncertainties in transport project evaluation’ (UNITE) which is a research project (2009-2014) financed by the Danish Strategic Research Agency. UNITE was coordinated by the Department of Transport of the Technical University of Denmark (DTU Transport) and carried out in cooperation with several Danish and international partners.
This following special issue of the European Journal of Transport Infrastructure Research (EJTIR) containing five scientific papers is the result of an open call for papers at the 1st International Conference on Uncertainties in Transport Project Evaluation that took place at the Technical...
Kim Bang Salling, Otto Anker Nielsen -
Cost overruns in transport infrastructure projects are prevalent and have been well documented in the literature; see, for instance, Flyvbjerg et al. (2003), Odeck (2004 and 2014) and Cantarelli et al. (2010). Governments may therefore exert efforts to reduce overruns by implementing strategies such as quality assurance of cost estimates, whereby external consultants are engaged to assure the accuracy of estimates. However, the literature has to a lesser extent provided evidence on what governments do to combat overruns and whether those efforts work in practice. This paper provides such evidence for the case of Norway, where the government implemented a quality assurance regime for cost estimates above 500 million NOK in the early 2000. Apart from explaining the Norwegian quality assurance regime, the paper uses statistical inferences to compare the magnitudes of cost overruns in the pre-and post- quality assurance periods. The statistically significant derived results are as follows: (i) quality assurance has led to a reduction in cost overruns; (ii) quality assurance has not, however, led to improved accuracy of the estimates provided by the authorities – rather, it has led to systematic overestimation by the authorities; and (iii) external consultants are more accurate than the authorities. We conclude that the quality assurance regime is achieving the objectives of reducing cost overruns and that similar regimes should be considered for smaller projects where overruns have been shown to be very large.
Cost overruns in transport infrastructure projects are prevalent and have been well documented in the literature; see, for instance, Flyvbjerg et al. (2003), Odeck (2004 and 2014) and Cantarelli et al. (2010). Governments may therefore exert efforts to reduce overruns by implementing strategies such as quality assurance of cost estimates, whereby external consultants are engaged to assure the accuracy of estimates. However, the literature has to a lesser extent provided evidence on what governments do to combat overruns and whether those efforts work in practice. This paper provides such evidence for the case of Norway, where the government implemented a quality assurance regime for cost estimates above 500 million NOK in the early 2000. Apart from explaining the Norwegian quality assurance regime, the paper uses statistical inferences to compare the magnitudes of cost overruns in the pre-and post- quality assurance periods. The statistically significant derived results are as...
Cost overruns in transport infrastructure projects are prevalent and have been well documented in the literature; see, for instance, Flyvbjerg et al. (2003), Odeck (2004 and 2014) and Cantarelli et al. (2010). Governments may therefore exert efforts to reduce overruns by implementing...
James Odeck, Morten Welde, Gro Holst Volden -
Astrategic task assigned to large-scale transport models is to forecast the demand for transport over long periods of time to assess transport projects. However, by modelling complex systems transport models have an inherent uncertainty which increases over time. As a consequence, the longer the period forecasted the less reliable is the forecasted model output. Describing uncertainty propagation patterns over time is therefore important in order to provide complete information to the decision makers. Among the existing literature only few studies analyze uncertainty propagation patterns over time, especially with respect to large-scale transport models. The study described in this paper contributes to fill the gap by investigating the effects of uncertainty in socio-economic variables growth rate projections on large-scale transport model forecasts, using the Danish National Transport Model as a case study. Population, gross domestic product, employment, and fuel prices were analyzed to quantify their uncertainty for 5 year intervals over a period of 15 years. The output of this procedure was then used to implement model sensitivity tests. The results from the model sensitivity tests showed how the model output uncertainty grows over time, reflecting the increase in the uncertainty of the model variables. Furthermore, the resulting uncertainty temporal pattern was neither linear nor similar for the different model outputs investigated. This highlights the importance of investigating uncertainty for different model outputs, and also that a dynamic approach is required whenever the model has to provide mid-long time period forecasts.
Astrategic task assigned to large-scale transport models is to forecast the demand for transport over long periods of time to assess transport projects. However, by modelling complex systems transport models have an inherent uncertainty which increases over time. As a consequence, the longer the period forecasted the less reliable is the forecasted model output. Describing uncertainty propagation patterns over time is therefore important in order to provide complete information to the decision makers. Among the existing literature only few studies analyze uncertainty propagation patterns over time, especially with respect to large-scale transport models. The study described in this paper contributes to fill the gap by investigating the effects of uncertainty in socio-economic variables growth rate projections on large-scale transport model forecasts, using the Danish National Transport Model as a case study. Population, gross domestic product, employment, and fuel prices were...
Astrategic task assigned to large-scale transport models is to forecast the demand for transport over long periods of time to assess transport projects. However, by modelling complex systems transport models have an inherent uncertainty which increases over time. As a consequence, the longer...
Stefano Manzo, Otto Anker Nielsen, Carlo Giacomo Prato -
Transport models most often involve separate models for traffic assignment and demand. As a result, two different equilibrium mechanisms are involved, (i) the internal traffic assignment equilibrium, and (ii) the external equilibrium between the assignment model and the demand model. The objective of this paper is to analyse convergence performance for the external loop and to illustrate how an improper linkage between the converging parts can lead to substantial uncertainty in the final output. Although this loop is crucial for the performance of large-scale transport models it has not been analysed much in the literature. The paper first investigates several variants of the Method of Successive Averages (MSA) by simulation experiments on a toy-network. It is found that the simulation experiments produce support for a weighted MSA approach. The weighted MSA approach is then analysed on large-scale in the Danish National Transport Model (DNTM). It is revealed that system convergence requires that either demand or supply is without random noise but not both. In that case, if MSA is applied to the model output with random noise, it will converge effectively as the random effects are gradually dampened in the MSA process. In connection to DNTM it is shown that MSA works well when applied to travel-time averaging, whereas trip averaging is generally infected by random noise resulting from the assignment model. The latter implies that the minimum uncertainty in the final model output is dictated by the random noise in the assignment model.
Transport models most often involve separate models for traffic assignment and demand. As a result, two different equilibrium mechanisms are involved, (i) the internal traffic assignment equilibrium, and (ii) the external equilibrium between the assignment model and the demand model. The objective of this paper is to analyse convergence performance for the external loop and to illustrate how an improper linkage between the converging parts can lead to substantial uncertainty in the final output. Although this loop is crucial for the performance of large-scale transport models it has not been analysed much in the literature. The paper first investigates several variants of the Method of Successive Averages (MSA) by simulation experiments on a toy-network. It is found that the simulation experiments produce support for a weighted MSA approach. The weighted MSA approach is then analysed on large-scale in the Danish National Transport Model (DNTM). It is revealed that system...
Transport models most often involve separate models for traffic assignment and demand. As a result, two different equilibrium mechanisms are involved, (i) the internal traffic assignment equilibrium, and (ii) the external equilibrium between the assignment model and the demand model. The...
Jeppe Rich, Otto Anker Nielsen -
An important limitation of Cost-Benefit Analysis (CBA) is the inherent uncertainty in estimations of future welfare effects. In this paper, we argue that consideration of the ‘pricequality’ dilemma and the ‘communication’ dilemma is useful to explain and improve the handling of uncertainty in CBA. The ‘price-quality’ dilemma refers to the trade-off between the quality of welfare effect estimations and the costs of providing these estimations. Instruments to produce good quality effect estimates (including uncertainties) can be expensive both in monetary terms and time. We discuss the application of probabilistic traffic models as a promising example of how the ‘price-quality’ dilemma can be solved. The ‘communication’ dilemma refers to the observation that both a poor communication and a too prominent communication of uncertainties can cause problems for decision-makers. We argue that cognitive psychological theory provides useful perspectives to solve this dilemma, by providing a psychological framework which might help to explain why different types of people process CBA information differently. The results of this research may enhance first insights into the questions how the two dilemmas can be solved.
An important limitation of Cost-Benefit Analysis (CBA) is the inherent uncertainty in estimations of future welfare effects. In this paper, we argue that consideration of the ‘pricequality’ dilemma and the ‘communication’ dilemma is useful to explain and improve the handling of uncertainty in CBA. The ‘price-quality’ dilemma refers to the trade-off between the quality of welfare effect estimations and the costs of providing these estimations. Instruments to produce good quality effect estimates (including uncertainties) can be expensive both in monetary terms and time. We discuss the application of probabilistic traffic models as a promising example of how the ‘price-quality’ dilemma can be solved. The ‘communication’ dilemma refers to the observation that both a poor communication and a too prominent communication of uncertainties can cause problems for decision-makers. We argue that cognitive psychological theory provides useful perspectives to solve this...
An important limitation of Cost-Benefit Analysis (CBA) is the inherent uncertainty in estimations of future welfare effects. In this paper, we argue that consideration of the ‘pricequality’ dilemma and the ‘communication’ dilemma is useful to explain and improve the handling of...
Niek Mouter, Marc Holleman, Simeon Calvert, Jan Anne Annema -
Assessing the risks of infrastructure investments has become a topic of growing importance. This is due to a sad record of implemented projects with cost overruns and demand shortfalls leading, in retrospect, to the finding that there is a need for better risk assessment of transport infrastructure investments. In the last decade progress has been made by dealing with this situation known as planners’ optimism bias. Especially attention can be drawn to the use of reference class forecasting that has led to adjustment factors that, when used on the estimates of costs and demand, lead to cost-benefit analysis results that are modified by taking historical risk experience into account. This article seeks to add to this progress in risk assessment methodology in two ways: first it suggests to apply reference class forecasting (RCF) in a flexible way where the effort is focused on formulating the best possible reference pool of projects and second to apply overconfidence theory (OT) to interpret expert judgments (EJ) about costs and demand as relating to a specific project up for examination. By combining flexible use of RCF with EJ based on OT interpretation it is argued that the current adjustment factor methodology of RCF can be further developed. The latter is among other things made possible by the comprehensive project databases that have been developed in recent years. For this article the project database developed in the UNITE research project 2009-2013 has been employed. The presented simulation-based risk examination named SIMRISK is concluded to provide a new ‘in-depth’ possibility for dealing with uncertainties inherent to transport decision making based on socioeconomic analysis. In addition a further research perspective is outlined.
Assessing the risks of infrastructure investments has become a topic of growing importance. This is due to a sad record of implemented projects with cost overruns and demand shortfalls leading, in retrospect, to the finding that there is a need for better risk assessment of transport infrastructure investments. In the last decade progress has been made by dealing with this situation known as planners’ optimism bias. Especially attention can be drawn to the use of reference class forecasting that has led to adjustment factors that, when used on the estimates of costs and demand, lead to cost-benefit analysis results that are modified by taking historical risk experience into account. This article seeks to add to this progress in risk assessment methodology in two ways: first it suggests to apply reference class forecasting (RCF) in a flexible way where the effort is focused on formulating the best possible reference pool of projects and second to apply overconfidence theory (OT)...
Assessing the risks of infrastructure investments has become a topic of growing importance. This is due to a sad record of implemented projects with cost overruns and demand shortfalls leading, in retrospect, to the finding that there is a need for better risk assessment of transport...
Steen Leleur, Kim Bang Salling, Inga Pilkauskiene, Morten Skou Nicolaisen