The new Guidelines for the Geometric Design of Rural Roads and the transfer into the existing Road Network in Germany

Transcription

1 0 0 0 The new Guidelines for the Geometric Design of Rural Roads and the transfer into the existing Road Network in Germany Dipl.-Ing. Janette Zoesch (Corresponding author) University of Technology Dresden Faculty of Transportation and Traffic Sciences "Friedrich List" Chair for Road Planning and Road Design Hettnerstraße 0 Dresden GERMANY Phone: + 0 Fax: + janette.zoesch@tu-dresden.de Dr.-Ing. Thomas Jaehrig Federal Highway Research Institute (BASt) Brüderstraße Bergisch Gladbach GERMANY Phone: jaehrig@bast.de Word count:, words abstract, text, references + figures/tables x 0 words (each) =, words Dresden, November 0, 0

2 ABSTRACT 0 Rural roads, because of their traffic function level, are the most important roads after the motorway network in Germany. The new rural road design guidelines (RAL) were released in spring 0. Leaving a sectoral division of guidelines for alignment, cross section and intersection design the new RAL is an integrated guideline covering all parts and design parameters of the rural road design in Germany. Compared to highways and urban roads, the majority of road fatalities happen on rural roads. A design principle consisting of standardization and recognizability is expected to be the key factor for a suitable road safety. Both characteristics are reached by the definition of only four road types (design classes) for rural roads. This design classes hang on roads link categorization and function level. Tight specifications for the elements of the alignment, crosssections or the intersection design make each road type as uniform as possible within the same design class and provide noticeable differences to others. This design philosophy should prevent as far as possible human mistakes. Furthermore, it fosters the driver to avoid confusion as a strategy to enhance road safety. The current rural road network represents the state of the art in road design of the respective period of time. The success of the new design principle implies that the concept is transferable to the existing network. In that case, adjusted design values and parameters to adapt existing roads into design classes must be defined. This is realized with the preparation of guidelines to transfer the principle of the design classes on the existing network (M EKLBest).

3 INTRODUCTION 0 Rural roads, because of their traffic function level, are the most important roads after the motorway network in Germany. The new rural road design guidelines (RAL) () were released in spring 0. Leaving a sectoral division of guidelines for alignment, cross section and intersection design, the new RAL is an integrated guideline covering all parts and design parameters of the rural road design in Germany. Compared to highways and urban roads, the majority of road fatalities happen on rural roads. A new design principle that emphasizes standardization and recognizability is expected to be the key factor for a more suitable road safety. Both elements, standardization and recognizability, are reached by the definition of only four road types (design classes) for rural roads. The design classes depend on road link categorization and functional level. Design classes, with tight specifications of design parameters, not only reduce the high variety but even support the unity of road types ( recognizable ) and their distinctness to each other. The four classes specify the type of road operation, cross sections, the parameters of the alignment and the type of the junctions. However, each design class has different design parameters. In this way, the driver should recognize the design class ( recognizability ) only looking at the design parameters (FIGURE ). Especially the always visible longitudinal road mark has a high recognition value. Furthermore, design characteristics that affect driving speed are specific for the particular design classes and encourage appropriate driving behavior. The geometric design of roads and the corresponding design parameters are based on the planning speed (FIGURE ). This last is comparable with the design speed of former guidelines and the estimated th -percentile speed on a road. ( ) Separate lanes for non-motorized traffic are recommendes; however, it is not mandatory. FIGURE Design classes and design characteristics ().

4 Design class roads (EKL ) are mainly used for long-distance travel in the rural road network. Road users should be able to long distances in an acceptable travel time, in spite of high traffic volumes. For this reason, EKL roads are restricted to motor vehicles (no agricultural vehicles and non-motorized traffic allowed). The cross section of EKL roads is a continuous three-lane carriageway with alternating passing lanes (FIGURE ) in order to provide safe passing opportunities. The driving directions are separated by two solid lines with green marking in between. To meet the desired travel times along the link in the road network, a high planning speed of km/h (ca. mile/h) is used. Consequently, the alignment is more stretched and the intersections are grade separated. The roads of the design class EKL are used for national traffic and distances up to 0 km (ca.. miles). To ensure good quality of service, slow moving traffic like agricultural vehicles are separated. The cross section provides passing lanes by more than 0 % of each road direction (FIGURE ). The alignment should be stretched and signalized at grade intersections should be used FIGURE Passing principles on roads of the design class EKL (left) and the design class EKL (right) (). EKL roads are designed for regional traffic with distances up to km (ca.. miles). In general there are no restrictions for any road user, however in terms of traffic safety, to order separate lanes for non-motorized traffic are recommended. In this case, EKL roads are restricted to motor vehicles and agricultural vehicles (no non-motorized traffic allowed). The cross section design is a single, two lane carriageway. If there is a need for passing, road users have to use the lane of the oncoming traffic. In contrast to the past road design guidelines there is no requirement of any planned sections with passing sight distance. The alignment should be adapted to the terrain. Consequently, the design parameters are based on a planning speed of 0 km/h (ca. mile/h). At grade intersections or roundabouts connect EKL roads to other roads. Depending on traffic volume, signalized intersections may be needed. Roads of design class EKL are designed for local traffic with very low traffic volume (up to,000 vehicle/d). The road is more adapted to the terrain. There are no restrictions for road users. Motorized and non-motorized traffic share the road equally. The cross section consists of a single lane without any road mark for lane separation. However, there is a dotted line at each shoulder, at 0. m (ca. 0. yd.) distance from the edge of the road. In case of oncoming traffic, road users are expected to reduce their speed and pass by with attention. Because of the short travel distances of less than km (ca.. miles) and the low traffic volume there is no need for passing. This design philosophy should prevent human mistakes as far as possible. Furthermore, it fosters the driver to avoid confusion as a strategy to enhance road safety. The current rural road network represents the state of the art in road design of the respective period of time. The success of the new design principle implies that the concept is

5 transferable to the existing network. It is currently unknown, which problems may appear in using RAL on specific planning tasks in the existing network. Thus, in 0 the Federal Highway Research Institute (BASt) started a research project (). The aim is to prepare recommendations on how to apply the principle of design classes to the existing network. The recommendations should be composed in a bulletin, called M EKLBest. APPROACH Due to the success of the new design principle of the RAL, it is desirable that as many roads of the road network as possible are designed according to this principle. However, the design characteristics of roads in the existing network do not often correspond to the recommendations of the RAL. Because of economic reasons, the complete existing network cannot be adapted to these requirements in a short period of time. Furthermore, the RAL only apply to the construction of new rural roads, reconstruction, and improvement of existing rural roads. However, in practice there are also measures which are beyond the scope of the RAL. The aim of the research is to transfer the new design principle of the RAL into the existing road network. This explain why, the acceptable minimum requirements of the design characteristics must be defined. Falling below the minimum requirements, an existing road cannot obtain the design according to RAL. The design in this context should be understood as the related road mark, because of the high recognition value of the longitudinal road mark on the carriageway. The aim of the research project is to specify these minimum requirements of the design characteristics, as well as giving solutions on how to deal with the differences between design characteristics of the existing network roads, and the requirements of the RAL. As a result, the M EKLBest is to be prepared using these findings. At the first stage of the project there is a need for an adequate collective of test roads. The test roads should be roads of the existing network whose design characteristics should be compared with the requirements of the RAL. The M EKLBest is applicable for all prevailing roads in the existing road network. Then, the test roads had to cover a broad range of different design characteristics. For the preparation of the collective of the test roads, road administrations of the federal states of Germany were asked to propose suitable roads and road planning projects for investigation. The test roads were chosen according to the following selection criteria: roads in need of a new road marking, roads in need of a new upper layer and road marking, roads scheduled to be upgraded and equipped with a new road marking afterwards, roads scheduled to be equipped with cycle lanes or lanes for agricultural vehicles to change their type of road operation. At the second stage the following design characteristics of the test roads were determined: length of the respective road section, road function level, traffic volume, type of road operation, cross section (carriageway width, share in passing lanes), horizontal and vertical alignment,

6 0 intersection design, and design of the transition sections at the beginning and at the end of the respective road section. Most of the data was provided by the respective road administrations. If the road administrations were unable to provide the data, an instrumented vehicle of the Chair of Road Planning and Road Design of the Technical University of Dresden was used to take measurements of the alignment. At the third stage, the design characteristics of the test roads were compared with the recommendations of the RAL. The result is an overview between the recommendations of the road design guideline compared to the existing road design of the respective test roads. Based on literature reviews, research, and on best practice exchanges with road administrations, the minimum requirements of design characteristics have to be defined to accept a road marking according to a design class. These definitions meet the absolute acceptable minimum needed for standardized roads and recognizable road types. After that, solutions on how to deal with differences between the design characteristics of the existing roads and the requirements of the RAL have to be prepared. A possible solution could be a chart providing information for the road designer on how to deal with different situations. For example, how to split the elements of the cross sections when the carriageway width of the existing road is different to the requirements of the RAL, or how to deal with transition sections between conventional existing road sections and RAL compliant ones. All best practice solutions, hints and recommendations will later summarized in the guideline for the implementation of the design classes into the existing road network (M EKLBest). FIRST FINDINGS 0 In the current state of the research the collective of test roads comprise rural roads of the existing network. TABLE summarizes the number, the total length and the annual average daily traffic (AADT) of the test roads differentiated by the design classes. Design class Number of test roads TABLE Overview of the test roads Total length [km] / [miles] Annual average daily traffic (AADT) [vehicle/d] EKL ca.. / ca.., 0,00 EKL ca.. / ca..,00,000 EKL ca. / ca..,, EKL ca. / ca., These test roads confirm that the design characteristics of the existing roads in the road network are often different to the recommendations of RAL. The following sections describe the main problems.

7 Type of road operation According to RAL, the majority of traffic restrictions are imposed in the design classes EKL and EKL. For these road types are advised separated ways for agricultural vehicles and nonmotorized traffic. Roads of the existing network of EKL or EKL often do not comply with these recommendations. They are not restricted to slow traffic and do not provide a separate network for it. However, the separation of slow and fast moving traffic on EKL and EKL roads is important to meet the objectives of the level of service, the travel time and the travel distance. High expenses are necessary to adapt the existing situation according to RAL. On roads of design classes EKL and EKL, there are no restrictions for any road users in general. This minimizes such kinds of necessary expenses and simplifies the upgrade of the existing road to the standard of RAL. For these reasons, implementation of the principles of design classes into the existing road network is related to the type of road operation, which is more easily with the roads of EKL and EKL than with the roads of EKL and EKL. Cross section The cross section of EKL roads is characterized by continuous and alternated passing lanes. Most test roads of this category are still equipped with continuous and alternated passing lanes. There are only occasionally short single two lane road sections. For road safety in these sections, the existence of the continuous double lines and for recognizability the green marking between the continuous double lines is important. Research during the preparation of the RAL has shown that those double lines and the green mark influence lane behavior (sufficient distance to separation of driving directions), have marginal influence on rule-breaking passing maneuvers, and have a high acceptance by road users and the administrations (). According to RAL the cross section of EKL roads provides passing lanes on more than 0 % of each road direction. The passing lanes are important for the road safety; they provide safe passing opportunities, and for the level of service, they split slow and fast moving traffic () (). The test roads have passing lanes from % until % of each road direction, but only one test road has passing lanes with less than 0 % of each road direction. In this case the problem is that the recommendations of RAL cannot be met for economic reasons. In the existing network, cross sections are usually smaller or wider than the recommended cross section widths. Especially regarding carriageway width, it is important to find some solutions for the cross section element splitting. On smaller carriageway widths, it is important at last to reduce the shoulders, in order to avoid edge breaks and the soiling of the edge lines. The median of EKL roads can be reduced. The only important aspect is the existence of the green mark between the double lines. This can also be applied to two-lane road sections along roads of EKL. In the existing network, there is a possibility that the cross sections of the roads of the EKL do not have continuous and alternating passing lanes. Therefore, it is important that the median is also marked in the sections with only one lane per driving direction.

8 The carriageway width of roads of the EKL should not be smaller than.00 m (ca.. yd.). In this case, no EKL can be applied and there should be only two solid edge markings. Apart from the shoulders, the widths of all cross section elements should not vary along a road section. When variations in the width of the carriageway are present along a road section, the width of the shoulders should also vary. Thus, a homogeneous marking can be ensured. In case of wider carriageway widths, also the shoulders should be widening. The results of the literature analysis have shown that wide lanes animate to high speeds (). The marking of the shoulders shows to the drivers, the edge of his driving area. So the width of the shoulders has no influence on the speeds driven. Referring to the marking per se, the administrations of road construction suggested that avoiding phantom markings is an advantage. Road users can still see the old markings, which influence indirectly their driving behavior. Furthermore, reducing the costs of the marking is an important advantage. For example, refering to the roads of EKL, it is extremely important to mark the median. When phantom markings are to be avoided, it is sufficient to change the marking at this point. Horizontal and vertical alignment 0 The parameters of the horizontal and the vertical alignment of the existing network roads only occasionally meet the requirements of the RAL. It is more difficult for EKL roads (much stretched alignment) than for EKL roads (much adapted alignment). Especially in mountainous regions the minimum radius, the maximum grade, and the vertical curve are not according to the RAL. For the administrations guidelines, where the differences are acceptable, where traffic engineering measures must be taken, and where it is not acceptable, requiring structural measures, must be defined. Intersection design Most of the junctions and conjunctions in the secondary network of the test roads meet the requirements of the RAL. However, for EKL roads the design of conjunctions with farm roads must be defined. The RAL doesn t have solutions for this. Design of the transition sections at the beginning and end of a road section 0 Another important point is the design of the transition sections between road sections of the existing network and the road sections that are to be designed according to the RAL. Literature analysis has shown that junctions and built-up areas are adequate transition sections (). For EKL roads, transitions can also be placed at the link. In this case the transition should be directed and not thinned. Details of the design of transition sections should still be researched and discussed with the administrations.

9 CONCLUSION 0 The majority of fatalities happen on rural roads. The RAL includes the latest research results and strategies with the aim to reduce these accidents and to improve road safety. For a successful realization of the principle of the RAL, it should also be transferable to the existing road network. However, this transfer is difficult because of the historically grown road network and also for his variety. Therefore, a research to transfer the RAL into the existing road network, that identifies the problems with the transfer, is being carried out. Some research examples are the separation of slow and fast moving traffic on EKL and EKL roads, the construction of continuous and alternating passing lanes at EKL roads, the construction of passing lanes on more than 0 % of each road direction at EKL roads, the splitting of elements of the cross sections by smaller or wider cross sections than the recommended cross section widths, the use of different parameters of the horizontal and the vertical alignment than the recommended parameters and the design of transition sections. Based on research results, recommendations for transferring the RAL principle to the existing road network will be devised. The guidelines for the transfer of the design class principle on the existing network (M EKLBest) will be prepared. Therefore a first approach exists. The guidelines could contain decision trees or check lists in order to consider the possibility of transfering the principle of the RAL to the existing road. They may also contain a collection of examples. ACKNOWLEDGEMENTS This study is the research project Adaption of the existing network on the design principle of standardized roads pilot project for using the M EKLBest. This is a project of the Federal Highway Research Institute (BASt). It started in 0 and will be finished in 0. The conduction of the project is carried out by the University of Technology Dresden, Chair for Road Planning and Road Design.

10 REFERENCES 0 0 () Road and Transportation Research Association (FGSV). Guidelines for the Design of Rural Roads (RAL). FGSV-Verlag, Cologne, 0. () Hartkopf, G. Sicherheit durch funktionsgerechte Standardisierung von Landstraßen. Presented at Colloquium Richtlinien für die Anlage von Landstraßen (RAL), Cologne, 0. () Lippold, Ch., and J. Zoesch. Anpassung des bestehenden Straßennetzes an das Entwurfskonzept der standardisierten Straßen Pilotprojekt zur Anwendung des M EKLBest. Project FE.00/0. Federal Highway Research Institute (BASt), Second interim report, Dresden, 0. () Lippold, Ch., K. Enzfelder, A. Bark, and R. Kutschera. Wirkung, Akzeptanz und Dauerhaftigkeit von Elementen der Fahrtrichtungstrennung auf Landstraßen. Project FE 0./00/AGB. Federal Highway Research Institute (BASt), Final report, Dresden, 0. () Lippold, Ch., G. Weise, and Th. Jaehrig. Verbesserung der Verkehrssicherheit auf einbahnig zweistreifigen Außerortsstraßen (AOSI). Project FE./00, AOSI part : Bewertung der Maßnahmen. Federal Highway Research Institute (BASt), Final report, Dresden, 0. () Jaehrig, Th. Wirksamkeit von Maßnahmen zur Verbesserung der Verkehrssicherheit auf einbahnigen Landstraßen. Graduate thesis. Chair for Road Planning and Road Design of the Faculty of Transportation and Traffic Sciences "Friedrich List" of the University of Technology Dresden, Dresden, 0. () Vieten, M., R. Dohmen, U. Duerhager, and K. Legge. Quantifizierung der Sicherheitswirkungen verschiedener Bau-, Gestaltungs- und Betriebsformen auf Landstraßen. In Berichte der Bundesanstalt für Straßenwesen, No. V 0, Bergisch Gladbach, 0. () Richter, T., and B. Zierke. Ergänzungen der Richtlinien für die Anlage von Landstraßen (RAL) zur Anwendung beim am Bestand orientierten Um- und Ausbau. Final report on FE 0.0/00/FRB on behalf of the Federal Highway Research Institute (BASt), Berlin, 0.

11 AUTHOR BIOGRAPHIES 0 Janette Zoesch was born in Werdau, Germany in. Since finishing her studies in Transport and Transportation Engineering at the University of Technology Dresden in 0, she is working as a scientific researcher at the University of Technology Dresden, Chair for Road Planning and Road Design. She is preparing two research projects on behalf of the Federal Highway Research Institute (BASt), FE.00/0 Anpassung des bestehenden Straßennetzes an das Entwurfskonzept der standardisierten Straßen Pilotprojekt zur Anwendung des M EKLBest [ Adaption of the existing network on the design principle of standardized roads pilot project for using the M EKLBest ] and FE.00/0 Räumliche Linienführung von Autobahnen [ physical line management at motorways ]. Thomas Jaehrig, Ph.D. was born in Dresden, Germany in. After finishing his studies in Transport and Transportation Engineering at the University of Technology Dresden in 00, he was working as a scientific researcher at the University of Technology Dresden, Chair for Road Planning and Road Design. Since 0 he work at the German Federal Highway Research Institute in the Traffic Engineering Department. Within this department he started working in the Section Technical Centre Asset Management and changed in September 0 to the Section Highway Design, Traffic Control, Traffic Flow. He is responsible for research in the field of highway and motorway design and be a member of different groups regarding road design, human factors and safety analysis within the Road and Transport Research Organisation (FGSV). In 0 he finished his Ph.D. thesis titled Wirksamkeit von Maßnahmen zur Verbesserung der Verkehrssicherheit auf einbahnigen Landstraßen ; [ Effectiveness of Measures to improve Traffic Safety on single carriageway Rural Roads ].