192 research outputs found
Infrastructure measures versus ADAS for traffic safety: review of some prevailing evaluation methods and Grey Relational Analysis
No full textItem does not contain fulltextSession "Vehicle Automation & Behaviour", 23 november 200415 p
Transport Infrastructure Slot Allocation
No full textIn this thesis, transport infrastructure slot allocation has been studied, focusing on selection slot allocation, i.e. on longer-term slot allocation decisions determining the traffic patterns served by infrastructure bottlenecks, rather than timetable-related slot allocation problems. The allocation of infrastructure capacity among carriers is a major issue in various transport infrastructure sectors, and therefore a theoretical framework on slot allocation would be desirable to support rational decision-making on slot allocation. The current state-of-the-art of slot allocation research does not provide such a theoretical framework, and therefore a theoretical framework to analyze slot allocation problems has been developed in this thesis. The first step in the development of a theoretical framework to analyze slot allocation problems has been the specification of a conceptual framework, which includes the definition of key concepts such as capacity. Capacity has been defined as being dependent on conditions such as composition of traffic and traffic context as well as assumptions about the desired balance between capacity and quality-of-service. The next step was to review the current application of slot allocation in the railway and aviation sectors, and the potential application of slot allocation in the road and navigation sectors. Slot allocation is currently applied in the railway and aviation sectors, and slot allocation may potentially be applied in other sectors. This thesis introduces the important distinction between selection and scheduling slot allocation. In both the railway and aviation sectors, the tradition has been to integrate selection and scheduling slot allocation. This thesis, however, considers selection slot allocation as a separate slot allocation level. Separating selection and scheduling slot allocation enables the application to each level of different rules with respect to slot validity, valuation of alternative slot requests, etc. The desired characteristics of selection slot allocation have been formulated in this thesis by analyzing the main desires of carriers and other interested parties such as shippers and authorities. It has been concluded that selection slots should be valid for a significantly longer period than scheduling slots, and a semi-static slot allocation procedure has been proposed. Furthermore, the acceptability principle has been introduced as a basis to specify desired slot size. However, the specification of standard basic slots by the allocation body (at different levels to attain differentiation of slot size) is desirable. A semi-static slot allocation procedure implies that selection slot allocation decisions may be based on an explicit evaluation of selection slot requests. The selection problem may be analyzed using congestion theory, resulting in a generic specification of traffic supply and demand. The next step is to specify traffic supply in more detail by specifying capacity constraints. Examining various types of primary traffic processes, traffic service processes, and traffic externalities, capacity constraints have been formulated, which may be applied to different types of bottlenecks. Three categories of capacity constraints have been distinguished, i.e. homogeneous capacity constraints, linear capacity constraints, and non-linear capacity constraints. The next step is the specification of objectives. The (primary) objective of slot allocation may usually be specified as a linear objective function. Depending on the type and number of capacity constraints, various instances of selection slot allocation decision problems may be formulated. The corresponding optimization problems may be solved using an exact solution algorithm, but for various reasons this thesis proposes a greedy approximation instead. Besides a standard greedy algorithm for selection problems with a single type of capacity constraint, an extended greedy algorithm has been developed to solve problems with two or more different types of capacity constraints. The latter algorithm has been tested for a hypothetical case study. Three main conclusions have been formulated in this thesis. The first main conclusion is that selection and scheduling should be considered as separate slot allocation levels having a hierarchical relationship. Selection slot allocation is of primary importance and scheduling slot allocation is only of secondary importance, because selection decisions determine which traffic is facilitated and which is not. The second main conclusion is that the validity of slots is a compromise between stability and flexibility. To ensure a sufficient level of stability, a validity of at least 5 years seems reasonable for selection slots. To ensure a reasonable level of flexibility, infinite validity of selection slots (historic rights) is not desirable, and at least every timetable season the opportunity should be offered to reserve selection slots. The final main conclusion is that the objec-tives and constraints of the selection problem can be modeled as linear functions, and the resulting binary linear programming problem can best be solved with the greedy efficiency algorithm presented in this thesis. This efficiency algorithm does not provide an exact solution of the binary linear programming problem, but its results are more robust and are easier to interpret than exact solution approaches.Civil Engineering and Geoscience
Dynamic bi-level toll design approach for dynamic traffic networks
No full textThe subject of this thesis is the application of dynamic road pricing in dynamic networks.Both forms of dynamics represent the outstanding elements of this dissertation. Its objective is the formulation and testing of a design methodology for an optimized tolling system for road networks.Civil Engineering and Geoscience
Service reliability and urban public transport design
No full textThe last few decades have shown a substantial increase in personal mobility. Urban traffic and transport volumes have been increasing for years. However, the share of public transport in this mobility growth did not change much and still remains rather limited. To ensure the accessibility and liveability of our cities for future generations, however, a substantial quality leap in public transport is necessary. This will facilitate a desired modal shift from car traffic towards public transport, which is safer, cleaner and produces less congestion. In this thesis, we demonstrate that several promising opportunities exist to improve service reliability (i.e. the certainty of service aspects compared to the schedule as perceived by the user), being one of the most important quality aspects of public transport. Literature shows that in urban public transport substantial attention is given to ways to improve service reliability at the operational level. It is not clear how and to what extent strategic and tactical design decisions in public transport systems might affect service reliability. Only traffic light priority and exclusive lanes are considered during the planning of urban public transport in order to improve the level of service reliability. We expect that more instruments at these planning levels enable high-quality services at the operational level, especially with regard to service reliability. In this thesis, we present several planning instruments that facilitate enhanced service reliability. In addition, we show forecasting tools we developed and we introduce a new indicator that expresses the impacts of service reliability more effectively than traditional indicators, namely the additional travel time per passenger. This way, the assessment of public transport benefits will be substantially improved, thereby enabling cost-effective quality improvements. We show the impacts of unreliable services on passengers, being average travel time extension, increased travel time variability and a lower probability of finding a seat in the vehicle. We demonstrate how actual vehicle trip time variability (i.e. service variability) affects service reliability and passenger travel time. In order to gain insights into the mechanisms between these two aspects, we performed research based on empirical data of the public transport system in The Hague. Furthermore, we conducted an international survey of service reliability. Several traditional quantifications of service reliability are presented, such as punctuality and regularity. We demonstrate the shortcomings of these traditional indicators, namely a lack of attention for passenger impacts. Traditional indicators focus too much on the supply side of public transport, which does not allow a proper analysis of passenger effects. To deal with the shortcomings of traditional indicators, we developed a new indicator, being the average additional travel time per passenger. This indicator translates the supply-side indicators, for instance punctuality, into the additional travel time that a passenger on average needs to travel from the origin to the destination stop due to service variability. The average additional travel time may be calculated per stop or per line and enables explicit consideration of service reliability in cost-benefit calculations, since the level of service reliability may be translated into regular travel time. In our research we demonstrate that our indicator enables optimization of network and timetable planning and that the use of traditional indicators may lead to conflicting conclusions in terms of service reliability. We also demonstrate the benefits of using reliability buffer time (RBT, as described by Furth and Muller 2006) as an indication of the effects of uncertain arrivals for passengers (i.e. the variability of the average additional travel time per passenger). To improve service reliability through enhanced network and timetable design, we selected five planning instruments by analysing the causes of service variability. The main external causes are the weather, other traffic, irregular loads and passengers’ behaviour. Other public transport, driver behaviour, schedule quality and network and vehicle design are the main internal causes of unreliability. Since the arrival pattern of passengers is very important when calculating service reliability effects, we performed a passenger survey in The Hague. It showed that passengers tend to arrive at random at their departure stop if scheduled headways are 10 minutes or less. In the case of longer headways, passengers on average plan their arrival about 2 minutes prior to the scheduled vehicle departure time. Applying instruments during the planning stages will reduce the impacts of these causes. At the strategic level, these instruments are: - Terminal design; The configuration and number of tracks and switches at the terminal determines the expected vehicle delay and thus service reliability. - Line length; The length of a line is often related to the level of service variability and thus service reliability. - Line coordination. Multiple lines on a shared track may offer a higher level of service reliability than one line (assuming equal frequencies). The following instruments may be applied at the tactical level: - Trip time determination; In long-headway services, scheduled vehicle departure times at the stop, derived from scheduled trip times, determine the arrival pattern of passengers at their departure stop. Adjusting the scheduled trip time may affect the level of service reliability and passenger waiting time. - Vehicle holding. Holding early vehicles reduces driving ahead of schedule and increases the level of service reliability. The design of the schedule affects the effectiveness of this instrument. The terminal design instrument relates to (new) rail lines with tail tracks as terminal or short-turning facilities. For high-frequency, distributed lines, we recommend compact tail tracks with double crossovers directly after the stop. Concerning (new) lines with a clear break point in passenger pattern, we recommend to split the line or to apply holding points. For long-headway services we propose to use the 35-percentile value for scheduled trip time. And if parts of lines are very crowded, we suggest investigating the effects of coordination. A tentative cost-effectiveness assessment showed that the tactical instruments (trip determination and vehicle holding) are cost-effective in almost every case. Their benefits are substantial and the costs are nil. These instruments should be considered in the design of every public transport system. However, the vehicle holding instrument is only beneficial if the passenger pattern has a clear break point and trip time determination only is relevant in long-headway services. It is presented that strategic instruments have considerable benefits as well. Optimized terminal design enables enhanced service reliability. Coordination and shorter lines may result in reduced passenger travel times as well. However, these instruments may look costly due to necessary additional infrastructure and or (occasionally) additional vehicles. We demonstrated that the costs are limited in relation to the potential welfare benefits. We roughly estimated the costs of unreliability at \u80 12 million per year in The Hague and we estimated the potential savings at \u80 8 million per year by applying the five planning instruments we analysed in our research. The estimated costs of these instruments are assessed to be only a part of the benefits with a maximum of \u80 3 million per year, showing the added value of the instruments. The results of our international survey show that similar results are achievable in other cities as well. In this thesis we presented planning instruments that facilitate enhanced service reliability. To achieve a higher level of service reliability in practice, we recommend considering service reliability explicitly in the design of infrastructure networks, service networks and timetables using our developed control framework and tools. Service reliability effects should be incorporated in a sophisticated way into cost-benefit analyses of public transport projects, using the average additional travel time per passenger we introduced. This way, welfare gains and additional revenues may be calculated. Optimized strategic and tactical design improves service reliability and also simplifies the operational process with regard to service reliability. Enhanced service planning will allow passengers to benefit from improved service reliability tomorrow!Transport and PlanningCivil Engineering and Geoscience
Design of multimodal transport networks: A hierarchical approach
No full textMultimodal transport, that is using two or more transport modes for a trip between which a transfer is necessary, seems an interesting approach to solving today's transportation problems with respect to the deteriorating accessibility of city centres, recurrent congestion, and environmental impact. Combining private transport and public transport in a truly multimodal transport system offers opportunities to capitalise on the strengths of the various systems while avoiding their weaknesses. The requirements for such a multimodal transport system, however, are high. Travellers have to be aware of the possibilities to change modes and the related benefit. Thus high quality travel information is crucial. Transfers between transport modes and services should be seamless, setting new standards for the design of transfer nodes and for the synchronisation of time-tabled transport services. Multimodal transport requires new organisational and financial arrangements between all actors involved. The most fundamental component of a multimodal transport system, however, is the multimodal transport network that consists of networks for private transport, public transport, and other transport services that are part of the multimodal transport system, including of course the transfer possibilities between these networks. This thesis investigates the consequences of multimodal travelling for designing multimodal transport networks. It describes the characteristics of multimodal travel today and assesses its future potential. The analysis focuses on the way transport networks are organised in hierarchical network structures and determines the main mechanisms leading to these hierarchical network structures. Furthermore, an analysis is made of the role in a multimodal transport system of transport services other than private transport or public transport. The results provide new insights into the mechanisms determining hierarchical transport network structures. They show the potential impact of multimodal transport especially on the capacity requirements for public transport, and they show the possible roles of the various transport services that may be part of a multimodal transport system.TRAIL Netherlands Research School for TRAnsport, Infrastructure and Logistic
Dynamisch Railverkeersmanagement besturingsconcept voor railverkeer op basis van het Lagenmodel Verkeer en Vervoer
No full textSociety demands that railways should perform better than they do currently: their product must become more reliable and cheaper, and the railways must be able to react to changes in the market and the environment more flexibly. The starting point of this thesis is that in other industries market forces and innovations are key factors to the improvement of performance and that this must also be possible in the railway industry. The hypothesis is that, in spite of the restructuring of the railways during the nineties of the 20th century in Europe ("separation of infrastructure management and train operations"), the potencies of market forces and innovations are insufficiently exploited and that this to a large extent can be attributed to the fact that the processes within the railway industry are tightly interwoven. "Everything" seems to be connected with "everything", especially in the operational heart of the railways: the rail traffic system. This thesis consists of two parts: the Transport Layer Model and Rail Traffic Management. In the first part, a generic conceptual model for the functional analysis of the traffic and transport system is developed called the Transport Layer Model. In this model, the traffic and transport system is considered as a composition of services and markets. The Transport Layer Model is applied to divide the railways into subsystems, with the objectives of improving the opportunities for market forces and innovations, and structuring the role of the government. In the second part of this thesis, the control of one of these subsystems, the rail traffic system, is analysed. The systematic integration of feedback loops into the control cycle leads to the development of a new control concept called Dynamic Rail Traffic Management the application of which can make the production of rail traffic services more reliable, more flexible and cheaper.Trai
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