Krill behaviour as recorded by acoustic doppler current profilers in the Gullmarsfjord

Vertical distribution of sound scattering layers were observed using bottom deployed acoustic doppler current profilers (ADCP) during early spring of 1996 and autumn of 1997 in the Gullmarsfjord on the Swedish west coast. Variations in relative backscatter were interpreted in relation to horizontal water velocities, oxygen saturation as well as differences in the light, salinity and temperature regimes. Net catches revealed that much of the backscatter below 20-m depth was associated with the presence of krill, principally Meganyctiphanes norvegica.Horizontal currents seemed to influence the migration and distribution of krill, which showed weak vertical migration patterns with low abundance during periods of strong intermediate in- and outflows, while during periods with weaker currents, a more regular diel migration occurred. Horizontal water velocities >5 cm s⁻¹ seemed to have the potential to decrease the peak in the backscatter profile. Mean vertical migration rates of krill was 1 cm s⁻¹, while maximum vertical migration rates were estimated to be 2.5–3 cm s⁻¹. The range of the vertical migration was different in 1997 due to severe oxygen deficiency in the bottom water, which prevented the krill from descending >80 m. The commencement of vertical migration correlated closely to the seasonal light conditions. The descent was immediately triggered by sunrise, while ascent occurred with a delay of about 1 h at sunset.     

Brake Valve Timing and Fuel Injection: a Unified Engine Torque Actuator for Heavy-Duty Vehicles

A unified engine torque actuator for heavy-duty vehicles is developed in this paper. Based on averaging and identification of the instantaneous torque response for changes in brake valve timing and fuel flow, we derive a control oriented engine model of a six cylinder, 350 Hp turbocharged diesel engine, equipped with a compression brake. This work bridges the gap between the detailed compression crank angle based models developed in the engine design community, and the first order lag representation of diesel engine torque response used in the vehicle dynamics community. Moreover, we integrate the compression brake actuator with the service brakes and design a PI-controller that emulates the driver's actions during long descends on grades. The controller simply uses the engine speed measurement to activate the service brakes only when needed.     

Activity settings and travel behaviour: A social contact perspective

Using time-use data from Canada, Norway, and Sweden, this study briefly outlines the essence of the activity setting approach and illustrates one aspect of its usefulness by exploring the impact of social contact on travel behaviour. The activity system approach views behaviour in context. Activity settings are generic components of the activity system and studying them using time-use diaries can provide major insights into travel behaviour. Focusing on social contact, this paper characterizes the social environment in terms of social circle (interaction partners) and social space (location). The analysis shows that there are clear differences in the levels of social interaction across various groups, including those who work at home. The 1992 Canadian data showed people working at the workplace spend relatively more time with others, about 50% of total time awake. Working at home reduced the time with others to a low of 15.7%. when people worked at home the family benefited, almost doubling the time spent with them compared to those working at the workplace. Persons working at home only spend the most time alone. There is a tendency for persons with low social interaction to travel more. It is argued that individual need, or want, social contact and if they cannot find it at the workplace they will seek it elsewhere thus generating travel. Whether this is the result of need or opportunity is of minor relevance, what it does suggest is that working in isolation at home will not necessarily diminish travel but rather may simply change its purpose. This revised version was published online in June 2006 with corrections to the Cover Date.     

高速铁路对都市区一体化的影响 ——以伦敦、马德里和巴黎为例

高速铁路建设的最初目的是连接相距400~600 km的都市区.但是近年,都市地区的郊区及城市出现了一些边缘位置的高铁车站,距都市中心的距离约100 km.重点研究位于马德里(瓜达拉哈拉、塞戈维亚和托莱多)、伦敦(斯特拉特福德、艾贝斯费特和阿什福德)和巴黎(鲁瓦西—戴高乐、马恩河谷—谢西和马西)附近的9座外围高铁车站,分析它们对都市区及当地的影响,并提取对加利福尼亚州高速铁路项目可借鉴之处.     

The perception and image of shipping

The image of the shipping industry plays a vital role in developing maritime transport as a major future, sustainable transport alternative. In particular, it is crucial to understand the image the shipping industry has among young people and the anatomy of the concept in order to be able to effectively promote careers in shipping, to cultivate shipping as an attractive labour market and to develop attractive educational programmes. The focus of this paper is the image of the shipping industry. This study reports on the findings of a large-scale survey of the image of shipping- and image-related concepts among upper secondary school pupils in Sweden, Norway and Greece. We define and analyse empirically by means of multivariate statistical analysis the anatomy of the image concept. We identify various image dimensions, estimate how young people rate the shipping industry along these dimensions and estimate their relative importance to young people who are planning their future careers. The results from this study can be used as a base for describing and explaining the images that young people have of the shipping industry. Such knowledge is fundamental for deriving and developing constructive strategies to promote careers in shipping, to adapt shipping to the expectations of young people and to develop creative and relevant educational programmes. Finally, understanding the image of shipping among young people is important not only for the shipping industry, but for other stakeholders as well, such as ship-owners associations, trade associations, labour unions, transport authorities and administrations and policy makers at the national and supra-national level.     

Contractual PPPs for Transport Infrastructure in Spain: Lessons from the Economic Recession

In this paper, we analyse the successes and failures of contractual public-private partnerships (PPPs) for delivering and operating transport infrastructure in Spain from the award of the first toll highway concession programme to the present. To that end, we show the risk allocation principles used in Spain and explore the evolution of the contracting approaches over the years. We found that the performance was reasonably good until the arrival of the economic crisis in 2008. Taking advantage of that, we make a review of contractual PPPs for different transport modes and assess the impact that the economic crisis has had on their business performance and the capacity of the central and regional governments to fulfil their commitments with the private sector. This analysis enabled us to identify measures that, if had been applied, would have improved the resilience of these contract during the economic crisis.     

Single wheel hub motor failures and their impact on vehicle and driver behaviour

This research work studies the impact of single wheel hub motor failures on the dynamic behaviour of electric vehicles and the corresponding driver reactions. An experimental study in a moving-base driving simulator is conducted to analyse the influence of single wheel hub motor failures for motorway speeds. Driver reaction times are derived from the measured data and discussed in their experimental context. The failure is rated objectively on the dynamic behaviour of the vehicle and compared to the subjective evaluation. Findings indicate that critical traffic situations impairing traffic safety can occur for motorway speeds. Clear counteractions by the drivers had to be taken.     

On the use of “average delay” as a measure of train reliability

We investigate how passengers on long-distance trains value unexpected delays relative to scheduled travel time and travel cost. For scheduled services with high reliability and long headways, the value of delays is most commonly assumed to be proportional to the average delay. By exploring how the valuation of train delays depends on delay risk and delay length, using three different stated choice data sets, we find that the “average delay” approach does not hold: the disutility increases slower than linearly in the delay risk. This means that using the average delay as a performance indicator, a guide for operations planning or for investment appraisal will underestimate the value of small risks of long delays relative to large risks for short delays. It also means that estimated valuations of “average delay” will depend on the delay risk level: valuations will be higher the lower the risk levels in the study are.     

Modeling traffic's flow-density relation: Accommodation of multiple flow regimes and traveler types

This research investigates freeway-flow impacts of different traveler types by specifying and applying a latent-segmentation model of congested and uncongested driving behaviors. Drivers in uncongested conditions are assumed to drive at self-chosen speeds, while drivers in congested conditions are assumed to take speed as given and choose a spacing (between their vehicle and the previous vehicle). Several classes of driver-vehicle combinations are distinguished in a data set based on double-loop-detector pulses and a household travel survey. These classifications are made on the basis of vehicle type and gender, leading to class estimates of speeds and spacings. The segmentation model is specified as a logit function of density, weather, and vehicle type, leading to estimates of congested-condition probabilities. Unobserved heterogeneity is incorporated in all models via common error assumptions.Results indicate that segmentation models are promising tools for traffic data analysis and that information on travelers, their vehicles, and weather conditions explains significant variation in flow data. By clarifying a greater understanding of traffic conditions and traveler behavior explains much scatter in the fundamental relation between flow, speed, and density, can assist regions in their traffic-management efforts and engineers in their design of roadway facilities. Ultimately, such improvements to travel networks should enhance quality of life.