Shared pilot passage plan and navigational safety during pilotage

Navigating in confined waters with a pilot aboard requires that the pilot’s intention and plan is understood by all present on the bridge. The present study investigates the effect of having a detailed route plan and monitoring it in the context of pilotage. The aim was to see how the presence of a shared pilot passage plan in the Electronic Chart Display and Information System (ECDIS) affects the identification and recovery from navigational errors made by a pilot. Twenty participants, 10 with a shared route plan and 10 without, participated as navigators in a simulator scenario involving pilotage in the Oslofjord. Participants were bachelor students in nautical science. The navigation scenarios involved the intentional error by the pilot just before a predefined way point. Three measurements of relevance to navigational safety were recorded: (1) the time it took the participant to express concern, (2) the time it took the participant to correct the error (‘time to recovery’), and (3) the number of groundings. The study revealed that time to express concern and time to recovery were significantly much shorter for the group with a shared pilot passage plan presented in ECDIS than for the group without such a plan. Providing a bridge team with a shared pilot passage plan in ECDIS during pilotage might improve the ability to identify and correct navigational errors.     

Participating mass in colliding risers

One of the main challenges in estimating impact energy in collisions between marine risers is the assessment of the riser mass involved in the collision. Evidently the entire riser mass does not contribute to the collision. Hence, the question is: What is the equivalent riser mass which contributes to the impact energy? This article presents three different ways of estimating the riser mass participating in the collision energy. The first method is strictly experimental. The second method uses a numerical experiment together with system identification techniques. The third method is a strictly analytical method, which results in an asymptotically upper bounded estimate of the participating mass. Two risers are examined as case studies. The first riser is a 1 : 100 model scale riser used in collision experiments carried out at Marintek's towing tank in Trondheim, Norway. The second case uses a real world riser in use on the Troll B oil production platform operating in the North Sea. The proposed methods yield consistent and comparable results. Received for publication on Feb. 1, 1999; accepted on July 8, 1999     

Use of the box and Jenkins time series technique in traffic forecasting

This paper explores the use of recently developed time series techniques for short term traffic volume forecasts. A data set containing monthly volumes on a freeway segment for the years 1968 through 1976 is used to fit a time series model. The resulting model is used to forecast volumes for the year 1977. The forecast volumes are then compared to actual volumes in 1977. The results of this study indicate that time series techniques can be used to develop highly accurate and inexpensive short term forecasts. A discussion of the ways in which such models can be used to evaluate the effects of policy changes or other outside impacts is included.     

Rail infrastructure charging EU-directive,Swedish concerns and theory

The first railway package is being recast by the legislative bodies of the European Union. One point of departure in this paper is how Swedish agencies treat issues concerning marginal cost based charges, financing charges and allocation of scarce capacity and it discusses these issues from a welfare point of view, partly by use of theoretical modelling. It is seen here that the Swedish infrastructure manager (the Swedish Transport Administration) so far has no method for calculation of marginal costs as a base for charging, especially for costs of scarce capacity, and that the infrastructure manager is applying or discussing various methods for allocations of scarce track capacity. The EU-recast gives no guidance on principles for calculation of charges for scarce capacity, so we recommend the Swedish Transport Administration to develop such charges. The Administration seems to ignore important externalities that should be taken into consideration from a welfare point of view, with respect both to efficient charging and to allocation of scarce capacity. The analytical modelling part of the paper aims to derive these charges in principle, taking these externalities into account. If financing charges exceeding social marginal costs are applied, the model shows how to minimise the welfare loss of these increases. It also shows that financing charges should primarily be applied to market segments that cause large external costs from the operation of the train, where its customers have low valuation of wait time and delay time, where customers of other segments have high valuations of delay and where increased profits for other operators are induced.     

Optimal economic interventions in scheduled public transport

This chapter analyses appropriate regulatory instruments for public transport markets under monopoly and competition, respectively. For the monopoly case, the operator chooses too low supply, compared to welfare optimum. In contrast, for the competition case the operators choose too high supply, at least for the competition model that we have considered most appropriate. It is found that under monopoly a subsidy should be applied, while under competition taxation should be applied.     

Decreasing oxygen concentrations in the Gullmar Fjord, Sweden, as confirmed by benthic foraminifera, and the possible association with NAO

The deep Gullmar Fjord on the Swedish west coast may be subject to a trend of decreasing oxygen content of the bottom-water. Due to a non-uniform frequency of oxygen measurements before and after 1980, and small differences in the minimum concentrations, it is difficult to assess with certainty if this is true or not. We have used benthic foraminifera from three ultra-high resolution sediment records to try to find out if such a trend exists. The sediment records comprise the time between 1930 and 1996, with an almost year-based temporal resolution. The foraminiferal records show a significant change in faunal composition during the mid-1970's when it altered from a common Skagerrak fauna to an assemblage characterized by an opportunistic, low oxygen tolerant species; Stainforthia fusiformis. This species is an indicator of low oxygen environments of many Scandinavian fjords. The timing of this faunal change coincides with one of the first recorded severe low oxygen events in the Gullmar Fjord in the winter of 1973/1974. The change suggests that the Gullmar Fjord has actually been subject to a decrease in bottom-water oxygen concentrations. The reason for this change is not clear but here, for the first time, we present sediment records that suggest that there is a causal relation between variations in the North Atlantic Oscillation (NAO) indices and the marine environment. In the early 1970s the NAO-indices altered from a mainly negative phase towards a mainly positive period which is still ongoing. Positive NAO-indices (winter values) in the Skagerrak region are generally marked by westerly winds which normally prevent the exchange of bottom-water in the fjords, i.e., the oxygenation of the sea floor and the supply of oxygen to benthic life.     

Quality incentives and quality outcomes in procured public transport - Case study Stockholm

Gross contracts appear to be the most common contract form for procured public transport in Sweden and elsewhere. This contract form, it has been argued, gives weak incentives for operators to deliver the desired quality level. Therefore many procuring public transport authorities amend contracts with quality incentives.This paper examines how such quality incentives influence quality outcomes with focus on cancelled departures and delays. The main findings are that the introduction of quality incentives are correlated with both increases and decreases of measured quality outcomes.We hypothesise that the results are driven by underlying cost changes for achieving desired quality objectives that exceed the possible revenues from the incentives. In interviews with the Stockholm public transport authority (SL) and some operators, two central observations surface. The first is that there are causes for quality failures that are not solely the responsibility of operators and that these are therefore not fully reached by the incentives, and the second is that the operators believe that they have exhausted what they can do under the current contracts.     

Workshop report - Public policy and transport

This workshop considered the wider public policy goals of a range of transport interventions. Particular attention was paid to assessing the role of integration of the different components of the transport system and of the integration of transport with other economic sectors. This assessment was informed by Ray Pawson’s realist evaluation approach, with its emphasis on the inter-relationships between context, process and outcome. The context was provided by case studies covering small urban areas, large urban areas and inter-urban corridors. The three key processes identified related to a regulated system with public ownership and control, a deregulated system with private sector ownership (‘competition in the market’) and a system in which there was public planning of the transport system but private provision (‘competition for the market’). Outcomes can be assessed using cost-benefit analysis tools to determine impacts on economic welfare or more qualitative approaches can be used to determine the extent to which accessibility or sustainability goals have been achieved. The evidence provided suggests that wider public policy goals are more important for urban than for inter-urban transport and it thus in urban areas where integration should be pursued with most vigour. The most relevant process for achieving this would seem to be variants of the competition for the market model. Some policy recommendations are made and implications for further research and for future conferences assessed.     

An Iterative Approach to Road/Profile Identification Utilizing Wavelet Parameterization

A time domain simulation error method is presented in the following article for estimating the excitation of structural systems from local operational responses. The present study focuses on the case in which the location of the excitation is known a priori, as it is for the interaction of the road profile and the tyre patch for an automotive vehicle. The road profile is parameterized into coefficients using truncated sets of base functions which greatly reduce the number of unknowns in the resulting non-linear optimization problem. A complex non-linear model of a ground excited vehicle is utilized to illustrate the applicability and performance of the method.