Danish Road Directorate Research Articles

Ten years of experience with road noise auralisations

For more than a decade, The Danish Road Directorate has used auralisations to communicate the future road noise impact to the public. Auralisations are add-ons to the mandatory noise maps and assessments of noise exposed dwellings and people. Moreover, auralisations are very useful for public presentations like EIA etc. Road noise auralisations and presentations have been made to give the road's neighbours an impression and understanding of the impact, the road will have on the environment. Additionally, auralisations have been shown to be a very powerful tool in terms of explaining general acoustic terms and sound propagation e.g. the influence of wind direction and speed and the efficiency of future noise barriers of various heights. Presentation formats range from webpages to auditory presentations with calibrated headphones and overlaying introducing speak giving exact sound levels for the audience. Even videos and recorded soundscapes from specific locations have been used to create auralisations that are more trustworthy and recognizable for the audience. This presentation gives an overview of different formats of presentation and summarizes our experiences so far with different auralisations suiting the various cases of road projects. The use of simple auralisasions in Dynamic Noise Monitoring Maps will also be touched.

Optimised durable pavement rolling resistance

The road-transport sector has a significant impact on energy consumption. A relevant component of this energy usage is associated with rolling resistance (RR) between tires and pavement. In Denmark, CO2 emissions from road transport alone have been quantified as 4.6 Mt/yr. Replacing standard stone asphalt with durable low-RR pavements is expected to reduce CO2 emissions up to 1%. The Danish Road Directorate started, back in 2012, optimising a surface layer for reducing RR. The low-RR mixture was designed to provide a durable texture capable to meet all safety requirements. In 2016, two low-RR mixtures and reference asphalt concrete were paved on a test section. To evaluate the texture durability these mixtures were sampled at the construction site and tested with a circular road tester. The results show that the durability of low-RR pavements can be enhanced by using premodified binder, which reduces changes in texture properties and increases rutting resistance.

Development of requirements for design and steps for protection of the environment, illustrated by two major bridge projects in Denmark

This paper describes how the Danish Road Directorate (DRD) works with the development and execution of construction of large infrastructure projects. The paper covers two parts: On the one hand the framework for reducing climate and environmental impact, and on the other the challenge of norms and standards. As cases, we will use two major bridge projects. As part of the basis for decisions the planning phase of infrastructure projects aims at providing the best way of meeting society's need for mobility, yet balancing many factors such as cost, time and environmental impact. The latter includes using the latest knowledge on climate and environmental impact as well as on the life cycle from cradle to grave of the infrastructure as input for a focused and cost-effective climate action. The planning also comprises factors that determine how biodiversity can be maintained as well as other considerations for the surrounding environment, including protected nature and habitat areas. This is exemplified by the new Roskilde Fjord Link project. Another major project, the future road and railway bridge crossing the Storstrøm, provides examples of the optimization of the design assumptions, considering the risks associated with the geotechnical conditions and relevant load conditions such as ice and ship impact.

Examining the potential of textual big data analytics for public policy decision-making: A case study with driverless cars in Denmark

The simultaneous growth of textual data and the advancements within Text Analytics enables organisations to exploit this kind of unstructured data, and tap into previously hidden knowledge. However, the utilisation of this valuable resource is still insufficiently unveiled in terms of transport policy decision-making. This research aims to further examine the potential of textual big data analytics in transportation through a real-life case study. The case study, framed together with the Danish Road Directorate or Vejdirektoratet, was designed to assess public opinion towards the adoption of driverless cars in Denmark. Traditionally, the opinion of the public has often been captured by means of surveys for the problem owner. Our study provides demonstrations in which opinion towards the adoption of driverless cars is examined through the analysis of newspaper articles and tweets using topic modelling, document classification, and sentiment analysis. In this way, the research attends to the collective as well as individualised characteristics of public opinion. The analyses establish that Text Analytics may be used as a complement to surveys, in order to extract additional knowledge which may not be captured through the use of surveys. In this regard, the Danish Road Directorate could find the usefulness while understanding the barriers in the results generated from our study, for supplementing their future data collection strategies. However there are also some methodological limitations that need to be addressed before a broader adoption of textual big data analytics for transport policy decision-making may take place.

Denmark funds three projects to boost FCEV rollout, station network

The Danish Road Directorate has awarded a total of DKK10 million (US$1.5 million) to support three projects that will boost the rollout of hydrogen cars and other fuel cell electric vehicles in Denmark. The projects will deploy the world's first fuel cell powered funeral hearse, two new hydrogen stations, and 24 other hydrogen powered vehicles.

Car Drivers’ Experienced Level of Service on Freeways

The Danish Road Directorate sponsored a study to develop methods for quantifying car drivers’ experienced level of service on freeways. The results provide a measure of how well freeways accommodate car travel. To determine how traffic operations, geometric conditions, and other variables affect car drivers’ satisfaction, 188 randomly selected respondents were shown 80 video clips of roadway segments filmed from a driven passenger car. Video clips consisted of high-resolution video filmed through a windshield, side windows including exterior mirrors, and a rear window. Video clips also included a GPS-based speedometer. Respondents rated video clips on a six-point scale ranging from very satisfied to very dissatisfied. The result was 7,497 usable ratings. Four hundred to 450 variables described respondents’ answers to six background questions and the video clips, that is, roadway segment geometries, traffic operations, surroundings, weather, and so forth. Car driver satisfaction models were developed with cumulative logit regression and ordinary generalized linear modeling. The six presented models included three to 10 variables, which related significantly ( p ≤ .05) to satisfaction ratings. These variables were average speed, speed limit, width of hard shoulder, number of entries and other merge areas per mile, number of exits and other diverge areas per mile, flow of long vehicles per lane per hour, direction of sunlight, driver age, type of driver’s license, and driver yearly mileage. Models returned percentage splits of the six levels of satisfaction or average satisfaction. These splits or averages were transformed into a level of service.

Miocene deposits at Silkeborg, Jylland, and their influence on hydrology

A motorway was constructed in 2010–2016 through the suburbs of the city of Silkeborg (Fig. 1). The Danish Road Directorate wished to climate-proof the motorway against adverse future climate changes. The directorate collaborated with the Geological Survey of Denmark and Greenland (GEUS) to study the hydrological conditions. Studies of historical and projected climate-change-driven variations in groundwater levels in relation to urbanised hydrological fluxes were conducted by Kidmose et al. (2013, 2015). During the construction of the motorway, Miocene and Quaternary deposits were exposed in the slopes of the Gudenå valley and late-glacial glaciofluvial deposits were found in the valley floor. This paper focuses on the Miocene sediments and their influence on the local hydrological conditions.
 At Silkeborg the Gudenå valley is c. 35 m deep (Fig. 1). The surrounding terrain is a till plain. In the slope of the valley, glaciofluvial sand is found below the till. Miocene deposits are found below the glaciofluvial sand. The floor of the Gudenå valley is covered by c. 15 m thick glaciofluvial deposits, which rest on Miocene deposits. In borehole no. DGU 87.907 49 m of Miocene deposits belonging to the Vejle Fjord Formation are recorded, consisting primarily of marine clay with minor occurrences of sandy deposits. About 12 km south of Silkeborg lower Miocene deposits are seen in outcrops and boreholes (Fig. 2). Here the fluvial Addit Member of the Billund Formation (Rasmussen et al. 2010) is separated from the underlying marine Vejle Fjord Formation by a sharp erosional contact (Rasmussen 2014).

Effect of mixing time on reclaimed asphalt mixtures: An investigation by means of imaging techniques

This paper presents an application of imaging techniques to investigate the distribution of reclaimed asphalt and air voids within gyratory compacted specimen. Stone Mastic Asphalt specimens containing reclaimed asphalt, were produced at five different laboratories participating in the collaborative project Re-Road: University of Nottingham, Belgium Road Research Centre, Danish Road Directorate, TU Braunschweig and Laboratoire Centrale de Ponts et Chaussees (now IFSTTAR). This study applies the X-ray Computed Tomography and Optical Microscopy techniques to view the internal structure of the specimen with particular focus on the air voids and reclaimed asphalt distributions within the specimen. The observations revealed that with doubling the mixing time the reclaimed asphalt is well mixed with the fresh materials within the gyratory compacted specimen and also the air voids distribution along the specimen height result to be more consistent.

Effective Implementation of Knowledge Management Strategies and the Key Roles of Knowledge Ambassadors in Strategy Integration

The purpose of this study is to examine how knowledge management strategies can be implemented effectively across divisions and what role change agents in the shape of so called ‘knowledge ambassadors’ can play in actively supporting knowledge sharing and effective integration of knowledge management strategies. Through a three year longitudinal participative case study the implementation of a knowledge management strategy is examined within the Danish Road Directorate and its seven geographically dispersed divisions. The results of the study reveal different steps and key activities in effective implementation of a knowledge management strategy and how knowledge ambassadors play a vital role in effective integration of knowledge management tools, continuous support of knowledge sharing practices and in developing a knowledge culture within the organisation. The contributions of this paper lie in the participative and longitudinal examination of effective knowledge management strategy implementation across geographically dispersed divisions and the introduction of knowledge ambassadors as a key success factor in knowledge management strategy integration.

Assessment of Three Alternative Bicycle Infrastructure Quality-of-Service Metrics

Cities throughout the United States are increasingly interested in the design of bicycle facilities to attract new riders and improve the comfort of existing riders. In particular, transportation agencies increasingly use treatments such as cycle tracks, buffered bike lanes, and colored pavement to supplement or replace traditional facilities (e.g., bike lanes). To respond to this trend, transportation professionals require evaluation metrics that effectively assess design options and provide decision-support in the choice of bicycle facilities that best match local context. Recent research has produced several bicycle evaluation tools [e.g., bicycle level of service (BLOS)] that attempt to fill this need. This paper presents the results of a comprehensive, real-world comparison of three leading bicycle evaluation tools: Highway Capacity Manual 2010 (HCM) BLOS, Danish Road Directorate BLOS, and the San Francisco, California, Bicycle Environmental Quality Index. Each evaluation tool was applied to a before–after evaluation of two bicycle facility installations in Washington, D.C. The tools were assessed with a consistent set of evaluation criteria, which included data and time requirements, sensitivity to key inputs, intuitiveness of the results, and soundness of the tool's theoretical basis. Intercept surveys of facility users were used to compare the tool outputs with actual user preferences. The results suggest several shortcomings in the HCM BLOS methodology that make it unsuited for assessing bicycle design options that include cycle tracks and other emerging bicycle facility types. Additional research is needed to develop a nationally accepted bicycle evaluation tool to reflect the growing variety of bicycle facilities in the United States.

Quality of Sediment in Detention Basins–Mapping of the Danish National Road Network

Use of the road infrastructure brings wear of the road surface and vehicles and loss of fuel components. This leads to pollution of the environment near the roads, due to run–off of road surface water to lakes and streams. The two thousand detention basins along the Danish main road network act as delaying basins for sudden large amounts of water and also collect substances which are injorious to the environment, before the water is led to lakes and streams. The Danish Road Directorate has examined the content of substances injorious to the environment in the sediment of 70 basins distributed in the whole country. Analysis of hydrocarbons, PAH, heavy metals and NaCl have been made. The analysis are used to determine the degree of pollution of the sediment in relation to the criteria set out by the Danish Environmental Protection Agency. The results show that at least 90 per cent of the detention basins have sediment which is defined as slightly polluted and at least 61 has sediment which is polluted. These high values are due to the content of hydrocarbons. The second largest source of pollution is nickel and the concentrations show that 20 per cent of the basins have sediment which is polluted by nickel. The highest concentrations of substances injorious to the environment are around Copenhagen and Odense and on the stretch between Kolding and Randers. The content of PAH and heavy metals has been compared to analysis from 38 natural Danish lakes. The analyses shows that there is no marked difference between the measured levels of pollution in detention basins and natural lakes. Hydrocarbons have been compared to two natural lakes and here the difference is very considerable.

Noise Classification for Tendering Quiet Asphalt Wearing Courses

Road administrations request noise reducing pavements and the industry has introduced new products claimed to have noise reducing properties. As a cooperative effort, the Danish Road Directorate, the paving industry and consultants have established a system for specifying such asphalt wearing course systems. Road administrations can now tender pavements with a certain class of traffic noise reduction, based on the Close Proximity (CPX) noise measurement method, ISO/CD 11819-2.The system represents a first Danish attempt to contract road works comprising noise reducing asphalt wearing course systems based on their functionality. Further development is foreseen concerning the CPX measurement accuracy and the acceptance criteria to be used in contracting.

CO2 Emission Reduction by Exploitation of Rolling Resistance Modelling of Pavements

Approximately one third of the Danish CO2 emissions come from the transport sector, whereof 95% is related to road transport emission. A reduction of the fuel consumption by approximately 3.3% on the road infrastructure will result in 48 million litres of saved fuel and 45.000 tons less greenhouse gases per year. Energy saving road pavements will therefore contribute to Denmark's quota in reaching the global climatic goals. The Cooee project addresses CO2 emission reduction by considering energy efficient and environmentally friendly transport systems and maintenance of the road infrastructure. By doing so, the Cooee consortium will exploit the research results in management of the Danish road infrastructure. To contribute to a sustainable Danish road infrastructure by reducing CO2-emission in a cost-effective manner, Cooee addresses the following: 1. Novel pavements with low rolling resistance, 2. Models of rolling resistance, 3. Wear and ageing of pavements, 4. Measurements of rolling resistance, 5. Asset management systems. The Cooee project is a collaboration between the Danish Road Directorate, Roskilde University, the Technical University of Denmark and NCC Roads. The Danish Strategic Research Council granted in 2011 2 million EUR to the Cooee project. The Cooee project plans to create two models: A comprehensive model of the contact zone between the tyre and the pavement, and a model for the pavement material. When these are in place, performance and optimization models will be established and implemented in the Danish asset management system “vejman.dk”. This will enable the Danish Road Directorate to include CO2-emission as a parameter in its strategic planning and maintenance of the Danish state roads. This paper presents the outline of the project, its expected results and the status.

Development of a screening method to assess flood risk on Danish national roads and highway systems

A method to assess flood risk on Danish national roads in a large area in the middle and southern part of Jutland, Denmark, was developed for the Danish Road Directorate. Flood risk has gained renewed focus due to the climate changes in recent years and extreme rain events are expected to become more frequent in the future. The assessment was primarily based on a digital terrain model (DTM) covering 7,500 km2 in a 1.6 x 1.6 m grid. The high-resolution terrain model was chosen in order to get an accurate estimation of the potential flooding in the road area and in the immediate vicinity, but also put a high requirement on the methods, hardware and software applied. The outcome of the analysis was detailed maps (as GIS layers) illustrating the location of depressions with depths, surface area and volume data for each depression. Furthermore, preferential flow paths, catchment boundaries and ranking of each depression were calculated. The ranking was based on volume of depressions compared with upstream catchment and a sensitivity analysis of the runoff coefficient. Finally, a method for assessing flood risk at a more advanced level (hydrodynamic simulation of surface and drainage) was developed and used on a specific blue spot as an example. The case study shows that upstream catchment, depressions, drainage system, and use of hydrodynamic calculations have a great influence on the result. Upstream catchments can contribute greatly to the flooding.

Verification of rutting calculation for unbound road materials

An analytical-mechanistic calculation method for the evaluation of rutting (permanent deformation) in unbound pavement layers and subgrade has been developed at the Technical Research Centre of Finland (VTT) over a period of years. The calculation method was generated from the test results of accelerated pavement tests along with complementary laboratory tests carried out in Finland. The test methods complemented each other and offered new possibilities for research. The stress distribution studies showed that it is very important to calculate stress responses in the pavement with an elasto-plastic material model to avoid tensile stresses in unbound materials, especially when the asphalt layers are thin. Thus, the new calculation method is based on the elasto-plastic stress responses and corresponding shear strength capacities. The shear strength approach was used because the rutting is supposed to be dominated by the shear strength ratio. The objective of this study was to verify the calculation method against two accelerated pavement tests: one from the Danish Road Directorate and the other from the Swedish National Road and Transport Research Institute. The verification indicated that the material model gave reliable results.

Bridge owner's benefits from probabilistic approaches

The growth of national economies in the latter half of the twentieth century has resulted in steadily increasing traffic volumes on trading routes and in an increase in the demands placed on an ageing bridge stock. Ironically, economic growth has not resulted in an increase in the budgets available to bridge owners for maintenance of their ageing resource. The approach adopted by the Danish Road Directorate in addressing this challenge has been to exploit advances in scientific methods in the management of its bridges. The use of probabilistic approaches within the areas of capacity assessment of bridges, bridge management and ship impact assessments have resulted in substantial cost savings, and future maintenance and repair needs have been minimized. Examples of the various areas where the probabilistic approaches have been applied are given, and both the technical approach and the administrative and financial benefits are presented.

Pedestrian and Bicyclist Level of Service on Roadway Segments

The Danish Road Directorate sponsored a study to develop methods for objectively quantifying pedestrian and bicyclist stated satisfaction with road sections between intersections. The results provide a measure of how well urban and rural roads accommodate pedestrian and bicycle travel. To determine how existing traffic operations, geometric conditions, and other variables affect pedestrians' and bicyclists' satisfaction, 407 randomly selected Danes were shown video clips from 56 roadway segments filmed by a pedestrian walking and a bicyclist riding along the road. Respondents rated the roadway segments on a six-point scale ranging from very dissatisfied to very satisfied. This resulted in 7,724 pedestrian ratings and 7,596 bicyclist ratings. Roadway segments and video clips were described by 150 variables. Pedestrian and bicyclist satisfaction models were developed by cumulative logit regression of the ratings and the variables. The models included variables that related significantly (p ≤ .05) to the satisfaction ratings. Variables that significantly influenced the level of satisfaction were motorized traffic volume and speed; urban land uses; rural landscapes; the types and widths of pedestrian and bicycle facilities; the numbers and widths of the drive lanes; the volumes of pedestrians, bicyclists, and parked cars; and the presence of median, trees, and bus stops. The models returned the percentage splits of the six levels of satisfaction. These splits were then transformed into a level of service. The models provide traffic planners and others the ability to rate roadways according to pedestrians' and bicyclists' satisfaction and may be used in the process of evaluating existing roads, designing new roads, or redesigning existing roads.

Accident prediction models for urban roads

This paper describes some of the main findings from two separate studies on accident prediction models for urban junctions and urban road links described in [Uheldsmodel for bygader-Del1: Modeller for 3-og 4-benede kryds. Notat 22, The Danish Road Directorate, 1995; Uheldsmodel for bygader- Del2: Modeller for strækninger. Notat 59, The Danish Road Directorate, 1998] ( Greibe and Hemdorff, 1995, 1998). The main objective for the studies was to establish simple, practicable accident models that can predict the expected number of accidents at urban junctions and road links as accurately as possible. The models can be used to identify factors affecting road safety and in relation to ‘black spot’ identification and network safety analysis undertaken by local road authorities. The accident prediction models are based on data from 1036 junctions and 142 km road links in urban areas. Generalised linear modelling techniques were used to relate accident frequencies to explanatory variables. The estimated accident prediction models for road links were capable of describing more than 60% of the systematic variation (‘percentage-explained’ value) while the models for junctions had lower values. This indicates that modelling accidents for road links is less complicated than for junctions, probably due to a more uniform accident pattern and a simpler traffic flow exposure or due to lack of adequate explanatory variables for junctions. Explanatory variables describing road design and road geometry proved to be significant for road link models but less important in junction models. The most powerful variable for all models was motor vehicle traffic flow.

Swing Bridge across a Navigation Channel, Denmark

A double-leaf swing bridge has recently been constructed to span a 44-m-wide dredged navigation channel in Denmark. The channel connects the city of Naestved with the sea, and the bridge is a link in a new road bypassing Naestved. The Danish Road Directorate considered a total of 14 proposals from five consulting firms: five bascule bridges, four swing bridges and five hoist bridges. The swing bridge presented here was selected based on its building and maintenance cost advantages, aesthetics, functionality, reliability and environmental compatibility. Preservation of the shoreline was also a high priority.

EFFECTS OF TRAFFIC CALMING SCHEMES IN DENMARK

The traffic problems on main roads passing through town and village centres are mainly caused by traffic passing without consideration to inhabitants and local traffic, with speed considerably higher than the limit. This has led to many accidents, large problems with risk perception, environmental problems and a great local interest for improvements. The Danish Road Directorate decided to implement traffic calming schemes in several Danish towns which were appropriate to the towns and the defined problems, also including economy. The traffic calming schemes should be effective, the visual appearance satisfactory and the measures should adapt to the local urban and traffic environment. Safety should be improved and the number of accidents reduced. COWI has assisted the Danish Road Directorate with the evaluation of the traffic calming schemes in 21 towns. This paper presents the results of a before-and-after study of traffic calming schemes in Denmark. The general result of the traffic calming schemes was a reduction in the average traffic speed by 10 km/h. In towns with new roundabouts the average speed was reduced by 15 km/h. In some towns the average speed was reduced by 30-40% (17-26 km/h). Reduction in traffic speed by each of the different means (e.g. gateways, roundabouts including miniroundabouts, pedestrian refuges and central refuge islands for narrowing the carriageway, chicanes, road humps, including flat topped humps) is also presented in the paper. The paper concludes that by investing approximately 0.3 0.4 mill. £ per km in small urban areas, positive effects can be obtained on traffic safety, risk perception, and the environmental quality of the area. Transactions on the Built Environment vol 33, © 1998 WIT Press, www.witpress.com, ISSN 1743-3509