227 research outputs found
The TRB West Group
No full textIn 1979 the by now classic work on the pottery of the TRB West group of Jan Albert Bakker was published. In his book Bakker deals with the research history and typochronology of the TRB pottery. Also he gives a detailed account of the other TRB finds such as flint and stone artefacts and of course the most important TRB sites. Over the years this book has become a standard-work for anyone who is interested in hunebeds and their makers. The author wrote a new introduction to this reprint in which he describes how the book of 1979 came together and the research that has been carried out since then
Robustness of roundabout metering systems (RMS)
No full textA simple explorative study shows that roundabouts are too small to be equipped with permanently operating traffic lights. The conclusion of a recent, more detailed study was not fundamentally different to this: at a small two-lane roundabout with four legs and with leg-by-leg control the shortest green time is 11 to 13 seconds, irrespective of the volume of traffic on the least busy leg. This results in a great deal of unnecessary waiting time. Leg-by-leg control at a four-lane roundabout is therefore not regarded as a robust solution. In view of this, at small roundabouts incidental metering signals are used. At single lane roundabouts, metering signals provide a more balanced distribution of the waiting time, whereas at two-lane roundabouts, the metering signals also have the potential to improve traffic flow. This was shown as early as 2003, in research conducted in collaboration with the author. This article explains the theoretical background to the research. In addition, general design principles for roundabout metering signals (RMS) are deduced. In 2011, research carried out as part of a Master's thesis supervised by the author studied the robustness of RMS for various traffic loads and roundabout types. Two types of roundabout were studied: \u95 a standard turbo roundabout and \u95 a spiral roundabout. A simulation model was used that underestimated rather than overestimated the effect of an RMS. The results show that, even under less than optimum conditions, traffic performance of the whole roundabout was improved by approximately 10 %. Traffic performance in the relevant (saturated) leg improved by more than this, namely by 15-45 %. The reduction of time loss at all legs taken together is even greater: -20 % to -50 % in total, and as much as -70 % for the saturated leg. Notably, altering a dominant load pattern can even reduce waiting time in the leg with the metering light.Transport and PlanningCivil Engineering and Geoscience
A comparative analysis of Virtual Coupling Railway operations
No full textVirtual Coupling is a next-generation signalling concept conceived to increase railway capacity by bringing moving-block operations one step further to separating trains by a relative braking distance, like cars on the road. Thanks to a Vehicle-to-Vehicle (V2V) communication layer, trains can move in virtually coupled platoons which can be treated as single convoys at junctions to improve capacity. This concept however introduces the need for additional operational constraints, especially at diverging junctions, which could make capacity gains insufficient to justify investments. The railway industry is hence investigating the benefits that Virtual Coupling can offer with respect to moving-block and fixed-block signalling systems. This paper introduces operational principles and an innovative train-following model capturing operational states and corresponding transitions of Virtual Coupling train operations. A comparative capacity analysis is conducted for a portion of the South West Main Line in the UK. Promising results are obtained, showing that the biggest capacity gains of Virtual Coupling refer to operational scenarios normally found in practice with trains having service stops and using different routes. The analysis of multiple disturbed scenarios reveals that performance improvements of Virtual Coupling over moving-block are instead only marginal on low-speed networks.Accepted Author ManuscriptTransport and Plannin
Continuous-discrete choices of control transitions and speed regulations in full-range adaptive cruise control
No full textDriving assistance systems such as Adaptive Cruise Control (ACC) and automated vehicles can contribute to mitigate traffic congestion, accidents, and levels of emissions. Automated vehicles may increase roadway capacity, improve traffic flow stability, and speed up the outflow from a queue (1). The functionalities of automated systems have been gradually introduced into the market, such as in the case of Adaptive Cruise Control (ACC). The ACC assists drivers in maintaining a desired speed and time headway, therefore influencing substantially the performance of the driving task. On-road studies have shown potential safety benefits of ACC systems that are inactive at low speeds when they are activated (2-5). In certain traffic situations, drivers may prefer to disengage ACC and resume manual control (6). These transitions between automation and manual driving are called control transitions (7) and may influence considerably traffic flow efficiency (8) and safety (9). Recently, full-range ACC systems that can operate in dense traffic have been introduced into the market. These ACC systems are more likely to be active in dense traffic conditions and have a positive impact on traffic flow efficiencyGreen Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Transport and PlanningTransport and Plannin
Using drones in the last-mile logistics processes of medical product delivery: A feasibility case study in Rotterdam
No full textThe term last-mile delivery refers to the final leg of a business-to-customer service, in which products are shipped from a depot to a destination point by means of land transportation, such as vans and small trucks. Although these vehicles provide a common and easy way to consign products, companies are striving for new transport technologies to reduce congestion, infrastructure limitations and air pollution. An alternative to road-bounded vehicles that has recently gained attention is the adoption of drones in parcel delivery. Drone applications range from military training, surveillance, path recognition and shipment of perishable products in emergency situations. Research on drones as delivery vehicles is still in its early stages, with some practical trials carried out by leader companies such as Google and Amazon. However, the application of drones in the pharmaceutical sector for home deliveries of medical products, has not been investigated yet. To gain new insights into the feasibility of introducing drones in the delivery fleet, drone applications were studied for the delivery operations of the pharmacy BENU ’t Slag, in Rotterdam. Two scenario alternatives were tested using the Vehicle Routing Problem formulation. A Large-scale Neighborhood Search lgorithm was implemented to solve the problem and derive the performance indicators associated with each scenario. Performances were then analyzed through a comparative analysis. When drones were introduced in the delivery fleet, indicators showed improvements in environmental aspects, service time and delivery costs, with a reduction of 9% in CO2 emissions, 12% in servicetime and 5.6% in cost per item.Transport and PlanningTransport and Logistic
Optimal lane change times and accelerations of autonomous and connected vehicles
No full textThis contribution puts forward a flexible approach to model the decision-making or design controller for automated driving systems, where tactical-level lane change decisions and control-level accelerations are jointly evaluated based on iteratively solving an online optimization problem. The key idea is that automated vehicles determine lane change times and accelerations in the predicted future to minimize an objective function representing multiple criteria of driving safety, efficiency and comfort. The interactions between controlled vehicles and surrounding vehicles are captured in the objective function. The approach can be applied to model non-cooperative decision-making of autonomous vehicles with optimization of own cost and cooperative behavior of connected vehicles with joint optimization of the collective cost. The problem is formulated as a differential game where automated vehicles make decisions based on the expected behavior of surrounding vehicles. An efficient numerical solution algorithm is used to solve problem. The proposed model performance is demonstrated via numerical examples. The results show that the proposed approach can produce efficient lane-changing maneuvers while obeying safety and comfort requirements. Particularly, the approach generates optimal lane change times and accelerations in the predicted future, including strategic overtaking and cooperative merging scenarios.Accepted Author ManuscriptTransport and PlanningBiomechatronics & Human-Machine ControlTransport and PlanningOLD Intelligent Vehicles & Cognitive Robotic
Moving from intermodal to synchromodal transport: A maturity model applied to a case study in North Western Europe
No full textIn order to meet emission targets for 2050 in Europe transport needs to be executed more 2 efficiently. A promising way to make transport more efficient is synchromodal transport. When the 3 service provider has more flexibility to arrange transport, the utilization and use of intermodal transport, 4 such as rail, can be increased and emissions per unit transported are reduced. Synchromodal transport 5 requires a large change in way of working for shippers and logistics service providers that may seem 6 insurmountable. In this article a maturity model is developed for synchromodal transport that breaks this 7 large change down into several stages that companies go through when developing synchromodal 8 transport. In a case study, executed for several companies situated in Northwestern Europe the maturity 9 model is applied in practice to identify enablers and inhibitors of synchromodal transport.Transport and Logistic
Aging of Bitumen and Asphalt Concrete: Comparing State of the Practice and Ongoing Developments in the United States and Europe
No full textAging is a crucial factor in pavement performance and being able to determine its effect on a mixture is necessary to link its initial properties to the properties over time in order to ensure the intended service life. This is becoming more important now that climate change leads to increased variation in weather conditions, while environmental considerations cause changes in the constituent materials that are used. As a result, past experience is becoming less reliable. In this paper, the USA and European approaches to aging are compared, showing that those contain the same test equipment and almost identical conditions for aging. This allows the exchange of data and experience. The current tests are suitable for binders and give an indication of the sensitivity to aging. For short term aging, Rolling Thin Film Oven Test (RTFOT) conditioning gives a reasonable indication of bitumen aging during asphalt concrete production and construction. This only holds for penetration grade binders during hot mix production and construction. For long term aging, because of the many variables involved, developing a single test method to characterize aging sensitivity seems impossible. However, using more elaborate protocols in existing, practical tests can provide more information and the necessary input for kinetic aging expressions. A pressure aging vessel (PAV) protocol for testing at two temperatures and time intervals, specifically at 90 and 100 degrees Celsius and for 20 and 40 hours, respectively, is suggested. Using the same conditioning in characterizing materials for pavement construction and research will facilitate the exchange of data and enable faster developments.Alternate title: Review of Asphalt (Concrete) Aging Tests in the US and Europe.Pavement Engineerin
Network Design and Impacts of Automated Driving: An Explorative Study
No full textThis study explores a network configuration concept for vehicle automation levels 3-4 (according to SAE classifications) in an urban road network having mixed traffic and demonstrates its potential impacts. The authors assume automated driving will be allowed on a selection of roads. For the remaining roads, manual driving (although supported by assisting driving automation systems) will be compulsory. A static Multi-Class Stochastic User Equilibrium traffic assignment based on the Path-Size logit and a Monte Carlo-Labeling combination approach for route-set generation is adapted to model the behavioral differences of vehicles in mixed traffic. Two user-classes are distinguished: vehicles with automation levels 0-2 and vehicles with automation levels 3-4 having a different Passenger Car Unit to account for lower driving headways, lower Value of Time, and higher fuel efficiency. The results indicate a decrease in total travel cost with the increase in market penetration rate of higher automation levels, a decrease in total travel time, and a minor increase in total travel distance. Although in most cases vehicles with higher automation levels benefit more from the improvements, the rest of the vehicles do not suffer deterioration in their travel conditions in any scenario. Furthermore, a noticeable shift of traffic from roads with access function to roads with flow function and distributors is observed. Sensitivity analysis shows that the extent of changes in the impacts is not strongly dependent on the input parameters. Finally, a steady decline in total travel cost is observed with increase in market penetration rate of higher automation levels.Accepted Author ManuscriptTransport and Plannin
Does haste make waste? The human factors of overtaking land design
No full textThe aim of this research was to improve overtaking safety and efficiency through improvements in road signage, markings, geometry and speed control associated with the placement and layout of passing lanes. The approach of the research was to explore the effects of several types of overtaking lane treatments in the safety and controlled environment of a state-of-the-art driving simulator. It was found that under the most benign conditions there were no differential effects of the three treatments. With poorer visibility or more taxing road geometry, the drivers relied more heavily on the road markings and signage and the effects of the treatments become more pronounced. The sensitivity to the more "challenging" situations was borne out by the greater speed differential between merge area sections at these sites
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