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In search of the severity dimension of traffic events: Extended Delta-V as a traffic conflict indicator
No full textMost existing traffic conflict indicators do not sufficiently take into account the severity of the injuries resulting from a collision had it occurred. Thus far, most of the indicators that have been developed express the severity of a traffic encounter as their proximity to a collision in terms of time or space. This paper presents the theoretical framework and the first implementation of Extended Delta-V as a measure of traffic conflict severity in site-based observations. It is derived from the concept of Delta-V as it is applied in crash reconstructions, which refers to the change of velocity experienced by a road user during a crash. The concept of Delta-V is recognised as an important predictor of crash outcome severity. The paper explains how the measure is operationalised within the context of traffic conflict observations. The Extended Delta-V traffic conflict measure integrates the proximity to a crash as well as the outcome severity in the event a crash would have taken place, which are both important dimensions in defining the severity of a traffic event. The results from a case study are presented in which a number of traffic conflict indicators are calculated for interactions between left turning vehicles and vehicles driving straight through a signalised intersection. The results suggest that the Extended Delta-V indicator seems to perform well at selecting the most severe traffic events. The paper discusses how the indicator overcomes a number of limitations of traditional measures of conflict severity. While this is a promising first step towards operationalising an improved measure of traffic conflict severity, additional research is needed to further develop and validate the indicator.publishedVersio
Local self-determination, process-focus and subordination of environmental concerns
Get PDFGlobalization and region enlargement has increased the emphasis of local authorities on being competitive for inward investment and taxpayers. This can lead to a subordination of environmental concerns. In order to secure environmental and other national interests, planning and regulation at supra-local level is required, especially if the local authorities have different motivations and goals from the central government. The central government policy guidelines of the Norwegian planning system and the possibility for regional state authorities to make objections are an apparatus to protect national interests in planning. However, there has been a significant change in the central government’s practice when deciding on objections by regional state authorities against municipal plans since the new right-wing Norwegian government came into power. The losers from the changed practice are the environmental interests, widely defined. The new government’s prioritization of local self-determination and planning processes rather than contents resonates with key features of neoliberalism, but also with important elements of communicative planning theory.Local self-determination, process-focus and subordination of environmental concernsacceptedVersio
A stock-flow cohort model of the national car fleet
Get PDFPurpose
Various regulatory and fiscal policy instruments are in force to reduce the amount of greenhouse gases and local pollutants emitted by private cars. The incentives operate primarily—or exclusively—on the newest generation of cars. But how fast will technological developments affecting new vehicle models penetrate into the car fleet? The speed at which the adverse effects of private car use will be mitigated through the normal vehicle renewal process, or through an accelerated one, carries considerable interest. Suitable modelling tools are needed. This paper aims to demonstrate the usefulness and flexibility of a bottom-up stock-flow modelling approach to private car fleet forecasting and policy analysis.
Methods
In the BIG model of the Norwegian automobile fleet, the annual stocks and flows characterising the car fleet are specified as matrices of 682 mutually exclusive and exhaustive cells, formed by cross-tabulations between 22 vehicle segments and 31 age classes. New car registrations follow from a disaggregate generic discrete choice model based on two decades of complete sales data for individual passenger car models.
Results
Example projections are presented onto the 2050 horizon under a low carbon fiscal policy scenario as well as a business-as-usual scenario. The fiscal policy is seen to make a large difference in terms of long term fuel consumption and CO2 emissions.
Conclusions
Stock-flow cohort modelling of the automobile fleet is a powerful and handy tool for policy analysis. Even quite simple and straightforward accounting relations may provide important insights into the dynamics of fleet development. It is possible to incorporate, into the stock-flow modelling framework, interesting and useful behavioural relations, explaining aggregate automobile ownership and travel demand, scrapping and survival rates, or consumer choice in the market for new cars.publishedVersio
Predicting market allocations, user benefits and wider economic impacts of large infrastructure investments for freight transportation
Get PDFConventional cost-benefit analyses of infrastructure projects are often partial analyses in which only the transport market is assessed while adjacent markets are neglected. For large infrastructure investments, however, this is more often than not an unrealistic assumption, especially in the case of investments affecting urban areas where markets adjacent to the transport markets are believed to exhibit a large number of externalities. This paper suggests an alternative approach to tackling the problem; namely, modeling the entire Norwegian economy in a general equilibrium setting. We have developed a Spatial Computable General Equilibrium (SCGE) model for Norway that takes into account urban dynamics through New Economic Geography features. This means modeling centripetal and centrifugal economic forces that produce changes in urban clusters. We use it to calculate direct benefits and the wider economic impacts of infrastructure investments for freight transport in selected case studies. For one particular case study, we find wider economic impacts of 17.0% of the direct benefits for passenger transport and 3.7% for freight transport. This suggests, first, that appraisal of infrastructure projects is to underestimate the real benefits and, second, decisions based on conventional wider economic impact analyses that only take into account passenger transport will tend to overemphasize passenger transport relative to freight transport. We argue that goods and labor demand effects, i.e. effects in markets adjacent to the transport market, are important if we are fully to realize the effects of infrastructure investments.publishedVersio
Three performativities of innovation in public transport planning
Get PDFThe article scrutinizes planners’ stories of innovation in contemporary public transport planning in three Scandinavian contexts (Denmark, Sweden and Norway). This analysis is accomplished by adapting Judith Butler’s post-structural feminist critical theory on performativity to the planning context. This theoretical framework is used to illuminate how planning is dynamically renewed, revised and consolidated over time by the individual routine actions of planners. From this perspective, the research identifies a set of repetitive acts – as recognizing specific windows of opportunity, anticipate and respond to political signals and create arguments and means of communication and persuasion – that constitute the contemporary transformation of professional practice in relation to planning politics. This analytics of performativity reveals how professional planning practices engage with transformative capacities of reshaping, re-enacting and re-experiencing guidance for the future within a set of meanings and forms of legitimation. These findings are intended to contribute to present and future planning practice and education in Scandinavian countries and elsewhere.acceptedVersio
Local favoritism in at-large proportional representation systems
Get PDFPork barrel spending is typically attributed to the strategic behavior of political elites hoping to be electorally rewarded by voters residing in their districts. Such behavior is expected to depend on the incentives imposed by the electoral system. We estimate the causal effect of local representation in a closed-list proportional representation system where individual candidates have no clear electoral incentive to favor their hometown. Using data from Norwegian regional governments, we still find a hometown bias. We document that municipalities with a representative on the regional council from the same party as the regional governor tend to obtain more funding for local investments. Citizens also tend to vote more often for parties whose gubernatorial candidate is from their own hometown, consistent with expectations of particularistic benefits. A possible explanation is that regional council members are often recruited from local politics and remain loyal to their roots. We find no evidence that regional council experience affects politicians' future career prospects at the local level.acceptedVersio
Natural hazard experiences and adaptations: A study of winter climate-induced road closures in Norway
Get PDFThe effects of global climate change include more extreme weather events that harm lifeline infrastructure such as road access. The questionnaire-based study takes a unique natural experiment approach to subjective personal experiences and perceptions of lifeline vulnerability in two seaside communities in Norway that have been sporadically isolated due to avalanches, heavy snowfall, and/or snowdrifts. The enquiry aims at filling a research gap on sudden winter climate-induced disconnections and road travel hazards in advanced societies. The results show that weather-induced road closures lead to worries about road travel and practical problems, but also that many people are able to adjust to reduce their vulnerability. The authors concluded that community characteristics such as available services and social and human capital are important for understanding people’s vulnerabilities, worries, and hazard preparedness.Natural hazard experiences and adaptations: A study of winter climate-induced road closures in NorwaypublishedVersio
Cross-comparison of three surrogate safety methods to diagnose cyclist safety problems at intersections in Norway
No full textAliaksei Laureshyn, Maartje de Goede, Nicolas Saunier, Aslak Fyhri, Cross-comparison of three surrogate safety methods to diagnose cyclist safety problems at intersections in Norway, Accident Analysis & Prevention, Volume 105, 2017, Pages 11-20, ISSN 0001-4575, https://doi.org/10.1016/j.aap.2016.04.035.Relying on accident records as the main data source for studying cyclists’ safety has many drawbacks, such as high degree of under-reporting, the lack of accident details and particularly of information about the interaction processes that led to the accident. It is also an ethical problem as one has to wait for accidents to happen in order to make a statement about cyclists’ (un-)safety. In this perspective, the use of surrogate safety measures based on actual observations in traffic is very promising. In this study we used video data from three intersections in Norway that were all independently analysed using three methods: the Swedish traffic conflict technique (Swedish TCT), the Dutch conflict technique (DOCTOR) and the probabilistic surrogate measures of safety (PSMS) technique developed in Canada. The first two methods are based on manual detection and counting of critical events in traffic (traffic conflicts), while the third considers probabilities of multiple trajectories for each interaction and delivers a density map of potential collision points per site. Due to extensive use of microscopic data, PSMS technique relies heavily on automated tracking of the road users in video. Across the three sites, the methods show similarities or are at least “compatible” with the accident records. The two conflict techniques agree quite well for the number, type and location of conflicts, but some differences with no obvious explanation are also found. PSMS reports many more safety-relevant interactions including less severe events. The location of the potential collision points is compatible with what the conflict techniques suggest, but the possibly significant share of false alarms due to inaccurate trajectories extracted from video complicates the comparison. The tested techniques still require enhancement, with respect to better adjustment to analysis of the situations involving cyclists (and vulnerable road users in general) and further validation. However, we believe this to be a future direction for the road safety analysis as the number of accidents is constantly decreasing and the quality of accident data does not seem to improve.Cross-comparison of three surrogate safety methods to diagnose cyclist safety problems at intersections in NorwayacceptedVersio
Soundscape and perceived suitability for recreation in an urban designated quiet zone
Get PDFGreen urban parks can offer city dwellers a place to withdraw from traffic noise. However, the significance of the sonic environment for suitability for recreational activities and how to measure this in an appropriate manner, has not been given much research attention. The aim of the study was to investigate the relation between calculated estimates of noise and the soundscape disclosing its suitability for recreation, and to compare three methods of measuring soundscape in an urban park designated as a quiet zone in Oslo. A soundwalk (N = 14) and an on-site survey (N = 99) were conducted in three different noise zones inside the park, and an off-site survey was conducted outside the park (N = 99). The study indicated that the soundwalk method was better at discriminating between the calculated high, medium and low noise zones in terms of the effect on perceived annoyance of traffic noise and suitability for recreational activities and potential for restoration. People outside the park expected the perceived annoyance of the traffic noise inside the park to be higher, and the potential for stress recovery to be lower than those asked in the lowest noise zone inside the park. The study points at the importance of protecting against road traffic noise in urban green areas to facilitate for recreational activities, and brings up pertinent methodological issues for the research on soundscape.acceptedVersio
Does the influence of risk factors on accident occurrence change over time?
Get PDFA large number of studies have been made to assess the relationship between risk factors and accident occurrence. A risk factor is any factor that makes an accident more likely to occur. Very many risk factors have been identified, for example, being under the influence of alcohol while driving, driving on slippery roads, entering complex junctions, or driving in hours of darkness. Few studies have been made to determine whether the associations between risk factors and accident occurrence remain stable over time. This paper presents examples of studies that have replicated estimates of risk. All these studies were made within a given country, using the same method, to ensure that estimates of risk are comparable. The risk factors included in the paper are: daylight, horizontal curves, junctions, road surface conditions, precipitation, drinking and driving and driver age. For all these risk factors, their association with accidents has changed over time, mostly becoming weaker. A protective factor, snow depth, is also included. Its protective effect has become smaller over time. Possible reasons for the weakening influence of risk factors are discussed.submittedVersio