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Abate M.,Swedish Road and Transport Research Institute
Journal of Transport Economics and Policy | Year: 2014

Recent performance indicators in the European road freight transport sector show there is an excess capacity. To shed light on this, this paper studies two aspects of capacity utilisation in trucking: the extent of empty running and the load factor. Using a joint econometric modelling framework, the paper shows that they can be explained as a function of haul, carrier, and truck characteristics. For estimation, a unique dataset from the Danish heavy vehicle trip diary was used. The results indicate distance and being a for-hire carrier have a positive effect on capacity utilisation, whereas the effect of truck size is non-linear.


Bagdadi O.,Swedish Road and Transport Research Institute
Accident Analysis and Prevention | Year: 2013

Today, various measures are used to estimate the severity of a traffic conflict. However, these measures are all limited to estimating the crash risk and do not include any estimates of the possible consequences of a potential crash. In accident analysis the estimated severity of the event is related to the outcome of the crash, such as injury levels. This article proposes a new method for estimating the severity of safety critical events based on both an estimate of crash risk and an estimate of possible consequence that, in addition to a measure of safety margins, takes vehicle mass as well as the relative speed of the involved road users into consideration. The article compares the estimated severity of 61 conflicts and 9 accidents of the proposed method with the traffic conflict technique. The results from the severity estimates of our proposed method show a significant difference in the severity levels of events involving vehicles with similar mass compared to critical events involving vehicles with dissimilar mass and events involving pedestrians. The proposed method gives the possibility to compare different conflicts, with regard to severity, with each other regardless of what type of conflict it is, e.g. intersection or rural road, or what kind of road users that are involved. In addition, an event classification, i.e. serious or very serious event, based on the severity estimate of the proposed method, shows promising results indicating that the severities are estimated in a homogenous way. The article concludes that our proposed method of estimating the severity of critical event seems to be able to reflect the dangerousness in a more realistic way than the traffic conflict technique and should facilitate the development of traffic safety analysis methods. © 2012 Elsevier Ltd.


Abate M.,Swedish Road and Transport Research Institute
Transportation Research Part A: Policy and Practice | Year: 2016

Although the aviation industry is increasingly becoming important for Africa's economic development and integration, the ability of airlines to access foreign markets remains hindered by restrictive regulatory policies. Attempts have been made to fully liberalize the intra-African air transport market. Except for general assertions about the merits/demerits of liberalization, our empirical understanding of the welfare effects of such polices in Africa remains rudimentary. This study empirically measures the economic effects of air transport liberalization, mainly on two supply side variables: fare and service quality, measured as departure frequency. The empirical models evaluate how air fares and departure frequency respond to measures of openness in air services agreements, while controlling for other determinants. The results show up to 40% increase in departure frequency in routes that experienced some type of liberalization compared to those governed by restrictive bilateral air service agreements. Furthermore, there is a relatively larger increase in departure frequency in routes which experienced partial liberalization compared to fully liberalized ones. This can be explained by the diminishing marginal effect of progressive liberalization on departure frequency. While the effect of liberalization is substantial in improving service quality, there is no evidence of its fare reducing effect. © 2016 Elsevier Ltd.


Janhall S.,Swedish Road and Transport Research Institute
Atmospheric Environment | Year: 2015

Urban vegetation affects air quality through influencing pollutant deposition and dispersion. Both processes are described by many existing models and experiments, on-site and in wind tunnels, focussing e.g. on urban street canyons and crossings or vegetation barriers adjacent to traffic sources. There is an urgent need for well-structured experimental data, including detailed empirical descriptions of parameters that are not the explicit focus of the study.This review revealed that design and choice of urban vegetation is crucial when using vegetation as an ecosystem service for air quality improvements. The reduced mixing in trafficked street canyons on adding large trees increases local air pollution levels, while low vegetation close to sources can improve air quality by increasing deposition. Filtration vegetation barriers have to be dense enough to offer large deposition surface area and porous enough to allow penetration, instead of deflection of the air stream above the barrier. The choice between tall or short and dense or sparse vegetation determines the effect on air pollution from different sources and different particle sizes. © 2015 The Author.


Forward S.E.,Swedish Road and Transport Research Institute
Transportation Research Part F: Traffic Psychology and Behaviour | Year: 2010

To disregard the speed limit is the most frequently reported violation. High speed has been related to road traffic accidents and is the main reason for people being killed or seriously injured. There is evidence to suggest that speeding is related to beliefs which minimize the perception of risk. The aim of the following study was therefore to determine what motivates drivers to speed. An extended version of the Theory of Planned Behaviour was used to examine the role of attitudes, subjective norms, perceived behavioural control and descriptive norms. The participants were randomly selected from the general public. The results demonstrated the value of TPB in the prediction of speeding on a rural road and that positive beliefs had a stronger link to intention than negative ones. It was also able to demonstrate the significant effect of descriptive norm and distinguish between two different groups of intenders; one low in ambivalence and one high. The latter group is relatively unknown and future research is required to explore their needs and motives in some more depth. Finally, the role of gender was assessed and the results showed that driving experience and age were important factors explaining women's lower intention to violate. Furthermore, the model was able to predict male and female intentions equally well and the unique effect of the various constructs within the TPB was also very similar. The findings from this study call for more tailored interventions. © 2010 Elsevier Ltd. All rights reserved.


Bagdadi O.,Swedish Road and Transport Research Institute
Transportation Research Part F: Traffic Psychology and Behaviour | Year: 2013

Naturalistic driving studies permit the study of driving behaviour during every day driving. Such studies have a long duration and rare events such as near-crashes and even crashes do occur during the period of the study. This fact gives an opportunity to study events that are otherwise difficult to find. However, the vast amount of data recorded within these naturalistic driving studies demands a huge amount of manual work to identify hazardous situations. This paper concerns the development and validation of a new method, based on critical jerk, to identify safety critical braking events during car driving. The method was compared with one of today's most used method, which is based on the longitudinal acceleration measure. Both methods were applied on near-crash data from the 100-car naturalistic driving study previously carried out by the Virginia Tech Transportation Institute (VTTI). The data included 637 near-crashes. The results from the analyses showed that the critical jerk method performed approximately 1.6 times higher overall success rate than the method based on the longitudinal acceleration measure. In addition, a positive correlation was found between driver's safety critical braking event and crash involvement. The conclusion is that the critical jerk method is capable of detecting safety critical braking events and may also be used for assessing high risk drivers. © 2012 Elsevier Ltd. All rights reserved.


Kircher K.,Swedish Road and Transport Research Institute | Ahlstrom C.,Swedish Road and Transport Research Institute
Accident Analysis and Prevention | Year: 2012

The crash risk in tunnels is lower than on the open road network, but the consequences of a crash are often severe. Proper tunnel design is one measure to reduce the likelihood of crashes, and the objective of this work is to investigate how driving performance is influenced by design factors, and whether there is an interaction with secondary task load. Twenty-eight drivers participated in the simulator study. A full factorial within subject design was used to investigate the tunnel wall colour (dark or light-coloured walls), illumination (three different levels) and task load (with or without a visual secondary task). The results show that tunnel design and illumination have some influence on the drivers' behaviour, but visual attention given to the driving task is the most crucial factor, giving rise to significant changes in both driving behaviour and visual behaviour. The results also indicate that light-coloured tunnel walls are more important than strong illumination to keep the drivers' visual attention focused forward. © 2012 Elsevier Ltd.


Antonson H.,Swedish Road and Transport Research Institute
Environmental Impact Assessment Review | Year: 2011

Landscape is partly a social matter and has long been one of many aspects investigated in environmental impact work in road and railway planning. The focus on landscape has recently strengthened as Sweden is on its way to ratifying the European Landscape Convention (ELC). It is timely to examine how landscape is handled in environmental impact statement (EIS) preparation in everyday practice, a process involving many actors. This study examines the environmental impact assessment process for a large road project, More Efficient North-South Communications in Greater Stockholm, in terms of the behaviour of three actors, the developer, practitioner, and reviewer. In many respects, the results were rather far removed from several ELC intentions. The deficiencies primarily concerned public participation, comprehensive overview, competence, and stakeholder coordination. These deficiencies originated both inside and outside the environmental impact assessment process of the studied road-building project and cannot be attributed any single stakeholder. © 2010 Elsevier Inc.


Sandberg U.,Swedish Road and Transport Research Institute
Acoustics Australia | Year: 2012

It has been suggested that hybrid and all-electric automobiles are so quiet at low speed in electric drive that they constitute a safety hazard for pedestrians and bicyclists. This trait has been especially troubling to vision-impaired people who rely on sound cues to avoid approaching vehicles. Assumptions have been made linking the quietness of such vehicles with fatalities and serious injuries. The U.S. Pedestrian Safety Enhancement Act of 2010, requires the use of Audible Vehicle Alerting Systems (AVAS) in hybrid and all electric vehicles. Rules are now being developed and are expected to be issued by January 2014. Similar regulations are being promulgated in Japan and the European Union. The UN/ECE is developing a Global Technical Regulation after extensive preparatory work. SAE International and ISO are developing a method of measuring the lowest accepted noise level for vehicles. This article first notes firm evidence that the noise difference between electric-driven and internal combustion engine (ICE) vehicles exists only at speeds below about 20 km/h; also that AVAS makes vehicles traveling at low speeds detectable from a longer distance, absent masking background noise. Some electric and hybrid cars on the market already have AVAS installed. The author explores the assumptions related to the problem in regard to traffic safety and the harmful effects of noise on humans. One statistical study from the United States seems to suggest that vehicles driven in electric mode cause relatively more accidents involving pedestrians than do ICE vehicles. However, multiple studies in the U.S., Japan and Europe leave this causal relationship unconfirmed. The author then shows that quiet vehicles, very hard to hear when approaching at low speeds, existed in urban traffic already many years before hybrid cars became common, and if quietness would create accidents this should have been apparent already earlier and not be something occurring only when hybrid and electric cars entered the market. A number of non-acoustical ways to alert pedestrians, not the least blind people, of quiet vehicles near them are discussed and suggested in the article. The article also describes the intensive work to explore the problem as well as to develop and specify AVAS systems that has been made from 2008 until now. The author argues that it would be more beneficial to human health and safety to reduce the maximum noise of vehicles rather than increasing the minimum noise of them. Consequently, the article ends with the recommendation to discontinue the work with AVAS, to limit rather than require the use of such systems, and instead focus on limitation of the worst masking noise emissions in urban areas.


Grahn-Voorneveld S.,Swedish Road and Transport Research Institute
Transportation Research Part A: Policy and Practice | Year: 2012

Usually transport systems, and roads in particular, are viewed as public goods. However, this is not always the case. In Sweden a large part of the road system is privately owned. Most of these privately owned roads are rural roads used by farmers and summer cottage owners, or used for forest transport. These roads are mainly provided by ownership associations.An important difference between public roads and these privately owned roads is that all investments- and maintenance decisions are made by the users themselves, who also have to pay the costs, whereas the usual case is that the owners/providers of a road-system are different agents than the users. Here the question is not how to charge the roads but how to split the costs of the roads among the users in an efficient and " fair" way.The motivation of this paper is the practical problem of how such an ownership association can divide the costs for the road network among the members in an efficient and " fair" way. The problem is treated from a game theoretical point of view, making use of the Shapley value. This means that the problem is associated with a game - a mathematical representation of the conflict situation. The Shapley value is a very important solution concept for cooperative games, like the game in this case. For games corresponding to this specific type of problems, it is shown that the Shapley value has excellent properties, such as beeing an element of the core, and beeing very easy to compute. © 2012.

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