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This study aimed to better understand nitrate transport in the soil system in a part of the state of North Rhine-Westphalia, in Germany, and to aid in the development of groundwater protection plans. An advection-diffusion (AD) cell was used in a miscible displacement experiment setup to characterize nitrate transport in 12 different soil samples from the study area. The three nitrate sorption isotherms were tested to define the exact nitrate interaction with the soil matrix. Soils varied in their properties which in its turn explain the variations in nitrate transport rates. Soil texture and organic matter content showed to have the most important effect on nitrate recovery and retardation. The miscible displacement experiment indicated a decrease in retardation by increasing sand fraction, and an increase in retardation by increasing soil organic matter content. Soil samples with high sand fractions (up to 94 %) exhibited low nitrate sorption capacity of less than 10 %, while soils with high organic matter content showed higher sorption of about 30 %. Based on parameterization for nitrate transport equation, the pore water velocity for both sandy and loamy soils were significantly different (P < 0.001). Pore water velocity in sandy soil (about 4 x 10 high 3 m/s) was about 100 to 1000 larger than in loamy soils (8.7 x 10 high 5 m/s). On the other hand, the reduction in nitrate transport in soils associated with high organic matter was due to fine pore pathways clogged by fine organic colloids. It is expected that the existing micro-phobicity increased the nitrate recovery from 9 to 32 % resulting in maximum diffusion rates of about 3.5 x 10 high 5 m/s2 in sandy soils (sample number CS-04) and about 1.4 x 10 high 7 m/s2 in silt loam soils (sample number FS-02).
In most of the existing highway capacity manuals, level of service (LOS) of freeway weaving segments and ramp junctions is traditionally defined by the speed, volume or density in critical areas of merge, diverge and weaving manoeuvres. In that traditional concept several capacity values of different critical areas (merge, diverge, weaving) as well as upstream and downstream basic freeway segments within the influence areas are evaluated separately. In this paper, a new model which considers the total segment of freeway merge, diverge, and weaving as an entire object is introduced. A combined volume-to-capacity ratio is used for defining the LOS of the total segment. According to the probability and queuing theory, the volume-to-capacity ratio of the whole segment can be considered as a combination of volume-to-capacity ratios in the different critical areas under consideration. The parameters of the new model can be calibrated with field data. Those parameters are functions of the number of lanes on the freeways, the number of lanes in the on-ramps or off-ramps, the length of the acceleration, deceleration, or weaving sections. Varying the model parameters the function can be fitted to the existing capacity models for different types of weaving segments or ramp junctions. With this model, the traffic quality (LOS) can be obtained directly as a function of the volumes on the freeway and on the on-ramp or off-ramp respectively. The new model has the following advantages: a) a uniform function for all types of freeway weaving segments and ramp junctions, b) traffic quality assessment for all critical areas under investigation in one step, and c) easy calibration. The new model will be incorporated into the new edition of the German Highway Capacity Manual (HBS 201X).
Cycling and designing for cyclist in Germany: an overview of road safety, research and guidelines
(2016)
Cycling is considered a social, eco-friendly, pollution-free, low noise and healthy activity and mode of transportation. There are currently around 67 million bicycles in Germany. This number is expected to increase in the near future with greater use of electromotive assisted bicycles. Regarding the expected increase, there should be additional attention given to road traffic accidents involving cyclists. In 2014, 396 cyclists were killed in road accidents in Germany, which is 12 % of all road fatalities. Also in 2014, Germany reported over 78,000 injuries to cyclists. The majority of the fatalities (about 58 %) and 83 % of the serious injuries to cyclists occurred in urban areas. This paper will examine three aspects concerning cyclists. First, the paper will show the main current developments, for example the National Cycling Plan 2020, the effects of the road safety programme and provide an analysis of the German national accident statistics. Second, the paper will give an overview of the regulations, guidelines for road traffic and designing of cycling facilities. Lastly, this study will detail the current and completed research in Germany addressing cyclist. For example, the paper will discuss the topic "Accidents between Turning-off Trucks and Cyclists" Accidents between right turning trucks and straight riding cyclists often show massive consequences. Accident severity is much higher than in other accidents. The situation is critical especially due to the fact that, in spite of the six mirrors that are mandatory for ensuring a minimum field of sight for the truck drivers, cyclists in some situations cannot be seen or are not seen by the driver. Either the cyclist is overlooked or is in a blind spot area that results from the turning manoeuvre of the truck. At present driver assistance systems are discussed that can support the driver in the turning situation by giving a warning when cyclists are riding parallel to the truck just before or in the turning manoeuvre. The paper will describe the requirements for turning assist systems for trucks. The outcome of the study is an overview of the accident situation between right turning trucks and straight driving cyclists in Germany as well as a corresponding test procedure for driver assistance systems. Below are several other projects which will be investigated, too: Accident Risk and Acceptance of Traffic-Rules by Cyclists ; Safety Improvement in Terms of Using Bicycle Paths in the Opposite Direction ; Cycling in Mixed-Traffic ; Observation of Pedal Electric Cycles Riders to Identify Safety Concerns. These three aspects will provide the current situation on the topic of cyclist safety in Germany.
Rural roads (highways) in Germany have to provide both high road safety and an appropriate level of service in accordance with their function in the road network. Single carriageway rural roads often underperform these expectations. An analysis of severe accidents on rural roads found two main contributing factors. First, high or inappropriate speed leads to accidents caused by the loss of control of the vehicle. Second, unsafe passing manoeuvres related to a misjudgement of sight distance, speed of oncoming vehicles or a misjudgement of the driver vehicle's acceleration capability. On the five roads where unsafe passing manoeuvres were a main contributing factor to accident occurrence, single short passing lanes (600 m to 1.2 km) were built to provide safe passing. On the remaining two-lane sections passing was prohibited by road signs and road marking. This paper investigates the effect of this design change on the accident situation and on traffic flow. The research project is based on a before/after comparison of traffic and accident data. Traffic volume, vehicle types and their velocities as well as the time gaps between the vehicles were recorded at different cross-sections. The result shows a significant improvement in road safety. This improvement was especially noted for severe head-on crashes, which were reduced to almost zero. The analysis of traffic flow on these roads pointed out that the chosen lengths of passing lanes were sufficient for safe passing and thereby reduced the need for dangerous driving behaviour. The recommendations of this research were fundamental for the determination of the design parameters of the second highest design class (EKL 2) in the new German Rural Road Design Guideline (RAL) published in spring 2013.
According to an investigation in March 2008 by the Federal Ministry of Transport, Building and Urban Affairs (BMVBS) about 14,000 truck parking spaces are missing in the near of motorways in Germany. Beside constructional enlargement of rest areas, intelligent traffic systems ought to be used to detect automatically the occupancy rate of rest areas and to provide better demand management and also to achieve an increase of capacity of truck parking spaces. The essay describes the newly developed control procedure "Compact parking", which is currently under development by German Federal Highway Research Institute (BASt). The method achieves that a number of trucks are parking in a compact way, side by side and without a driving lane between them. With the help of dynamic displays above the parking rows, the drivers receive the needful information to park their vehicle in a parking row, in which other trucks have the same or an earlier departure time. This system is able to increase the rest area capacity in short-term, more quickly than constructional enlargement of rest areas.
As the data for road weather stations is used for online traffic control within section control systems, it is very important for the efficiency of the traffic control systems to be based on reliable data of a high quality. Therefore, a Test Site for checking the quality of road weather stations was established near Munich in Germany in 2003 and has been operational since then. In close co-operation with all participants (sensor manufacturers, road authorities, German Federal Research Institute, research and consultancy bodies), the overall goal was to improve the sensors" quality as well as to establish methods to detect failures in measurements. Furthermore, several improvements were carried out within the scope of the Test Site using the expertise of all participants and the infrastructure of the Test Site. The developments, reports and results obtained are both significant and helpful for manufacturers, road authorities, practitioners, research and consultancy.