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101.
102.
We investigated perceived travel possibilities (or subjective choice-sets, consideration-sets) of car and train travellers on the main corridors to the city of Amsterdam, The Netherlands, and associations with traveller and trip characteristics. We conducted secondary analysis on a survey sample consisting of 7950 train and 19,232 car travellers. Forty-five percent of train travellers had a car in their objective choice-set, 27% of them would however never use it for this trip. Trip destination city centre, trip purpose, paying for the trip, public transport commitment, traffic congestion and parking problems were associated with consideration of car as alternative. Forty-two percent of car travellers had public transport in their subjective choice-set. The ratio between perceived public transport and objective car travel time stood out as determinant of consideration-sets, next to destination city centre, trip purpose, travel time and private versus company car ownership. On average, car travellers’ perceptions of public transport travel time exceeded objective values by 46%. We estimated that if perceptions would be more accurate, two out of three car travellers that currently do not see public transport as an alternative would include it in their choice-set, and use it from time to time. This effect has strong theoretical and policy implications. 相似文献
103.
Jos N. van Ommeren Derk WentinkPiet Rietveld 《Transportation Research Part A: Policy and Practice》2012,46(1):123-130
The literature on car cruising is dominated by theory. We examine cruising for parking using a nation-wide random sample of car trips. We exclude employer-provided and residential parking. We focus on the Netherlands, where levels of on-street and off-street parking prices are locally the same. We demonstrate then that due to this price setting the average cruising time in the Netherlands is only 36 s per car trip. Furthermore, we show that cruising is not random. It is more common in (large) cities that receive more car trips, particularly for shopping and leisure activities. Cruising time increases with travel duration as well as with parking duration. Cruising has a distinctive pattern over the day with a peak in the morning, so the order of arrival is essential to parking. Because cruising has a spatial and time component, policies may be considered that reduce cruising time through flexible pricing of parking or improved information about vacant parking spaces. 相似文献
104.
Due to limited data availability only a few studies have been able to provide statistically significant evidence on cost overruns
in transport infrastructure investments and their systematic nature, and fewer still for road infrastructure investments.
The body of available evidence refers to the most economically developed countries, while very little evidence was found regarding
other countries. In this article the authors focus on cost performance of road infrastructure constructed through the National
Motorway Construction Programme in Slovenia. Methodologically the study departs from other studies in this field by building
on detailed expenditure data and not aggregate reports from the relevant institution. This enabled the analysis of four individual
project cost categories (construction cost, land acquisition damages and others) and comparably more accurate results. A representative
sample of randomly selected completed projects in the period 1995–2007 revealed that the cost overruns (19%; SD = 46.10%)
in the entire period studied do not appear to be higher than in other comparable studies. At the same time the study results
showed that cost overruns were unstable, i.e. much higher for older projects. 相似文献
105.
Orsola Rath?SpivackEmail author Roger?Kinns Nigel?Peake 《Journal of Marine Science and Technology》2004,9(3):109-116
We present preliminary results from our new ship motion model that includes both strong and weak three-dimensional interactions between environmental surface waves and ship bodies in arbitrary water depth. The linear solutions of steady flow using the new model agree well with those obtained using the Green function methods. When the Froude number Fn is large, the fully nonlinear solutions of our model are significantly different from linear solutions, even in calm water. The interactions between the ship and incident gravity waves are completely different from those in linear solutions even with small Fn and moderate-amplitude surface waves (e.g., Fn = 0.25 and a significant wave height of about 1–3m). 相似文献
106.
Kamlesh S.?VaryaniEmail author Appapillai?Thavalingam Parmeswarn?Krishnankutty 《Journal of Marine Science and Technology》2004,9(1):24-31
To improve the formulation of ship–ship interaction forces and moments in a mathematical model of a ship maneuvring simulator, we developed a new generic mathematical model for the overtaking maneuver. This process involves using the numerical results, which provide a potentially complete set of data from which (within the constraints of the numerical modelling) everything necessary can be acquired. We found that the new generic mathematical model is as accurate as the numerical model. It is also more accessible to a navigator, master, or pilot, who could use it on a palmtop computer by keying in a few numberical estimates of the size, position, and speed of the neighboring ship and receive almost instant aneous results, giving time for a refined strategy to be validated if necessary. These results can also readily be used by simulation program developers to simulate the worst possible scenarios. 相似文献
107.
Goutam Kumar?SahaEmail author Kazuo?Suzuki Hisashi?Kai 《Journal of Marine Science and Technology》2004,9(2):51-62
A computational method for improving hull form in shallow water with respect to wave resistance is presented. The method involves coupling ideas from two distinct research fields: numerical ship hydrodynamics and nonlinear programming techniques. The wave resistance is estimated by means of Morinos panel method, which is extended to free surface flow and considers the influence of finite depth on the wave resistance of ships. This is linked to the optimization procedure of the sequential quadratic programming (SQP) technique, and an optimum hull form can be obtained through a series of iterations giving some design constraints. Sinkage is an important factor in shallow water, and this method considers sinkage as a hydrodynamic design constraint. The optimization procedure developed is demonstrated by selecting a Wigley (C
B = 0.444) hull and the Series 60 (C
B = 0.60) hull, and new hull forms are obtained at Froude number 0.316. The Froude number specified corresponds to a lower than critical speed since most of the ships operating in shallow water move below their critical speed. The numerical results of the optimization procedure indicate that the optimized hull forms yields a reduction in wave resistance. 相似文献
108.
Roberto?MuscariEmail author Andrea?Di Mascio 《Journal of Marine Science and Technology》2004,9(4):158-170
A new model for the simulation of spilling breaking waves in naval flows is presented. The hydrostatic pressure is used in order to mimic the weight of the breaker on the underlying flow, as in the model of Cointe and Tulin, whereas the algorithm for detecting the breaking inception and the definition of its geometry are completely new and are suitable for the simulation of three–dimensional flows around ships hulls. The model has been implemented in a finite-volume code developed for naval flows, and its performances have been validated against experimental data for a submerged profile, an S60 hull in drift motion, and the US Combatant DTMB 5415 model on a straight course. 相似文献
109.
A 2D+T VOF fully coupled formulation for the calculation of breaking free-surface flow 总被引:1,自引:0,他引:1
Yann?AndrillonEmail author Bertrand?Alessandrini 《Journal of Marine Science and Technology》2004,8(4):159-168
We present the results of simulations obtained with a free-surface flow solver based on the following method. The free surface is simulated by the volume-of-fluid interface capturing method. This code solves the Navier–Stokes equations using a finite-volume method adapted to a structured or unstructured mesh. The system is constructed using a fully coupled approach. This global approach allows the simulation of complex flow as a breaking or merging wave. Moreover, with the use of a 2D+T decomposition, it is possible to simulate three-dimensional steady flow. 相似文献
110.
Choung Mook?LeeEmail author Dong Gi?Han Kwan Hyoung?Kang Sang Joon?Lee 《Journal of Marine Science and Technology》2004,8(3):117-125
The behavior of the flow passing a tandem oil fence, and the performance of the fence, were investigated by experimental and numerical methods. The flow characteristics between tandem fences were measured by the particle image velocimetry (PIV) method for the rigid and open free surface between the two fences in order to gather reference data for numerical investigations. A method of assessing a tandem fence by tracing the movement of an oil droplet around the fence is introduced. The effect of the current speed, the separation distance between the two fences, the relative draft of the two fences, and the water depth on the oil containment between the fences was investigated. 相似文献