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2023 | Buch

Road Planning - Freeways and Country Roads

verfasst von: Thomas Richter

Enthalten in: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik" , Springer Professional "Wirtschaft"

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Über dieses Buch

The book covers the planning and design of highways and country roads. The quality requirements for the road are derived from the network planning. After an excursus into the fundamentals of driving dynamics, the design elements are described in the site plan, in the height plan and in cross-section. After a detailed presentation of the intersection solutions, the necessary equipment is compiled.

This book is a translation of the original German 1st edition Planung von Autobahnen und Landstraßen by Richter Thomas published by Springer Fachmedien Wiesbaden GmbH, part of Springer Nature in 2016. The translation was done with the help of artificial intelligence (machine translation by the service DeepL.com). A subsequent human revision was done primarily in terms of content, so that the book will read stylistically differently from a conventional translation. Springer Nature works continuously to further the development of tools for the production of books and on the related technologies to support the authors.

Inhaltsverzeichnis

Frontmatter

1. Introduction

Summary

Roads outside built-up areas serve to connect nearby and far away regions and form the backbone of individual mobility and the exchange of goods. Germany’s central location in Europe and the increasing national and international connected social life require safe and efficient roads, not least to support economic performance. This book takes up the aspects of planning, design and operation of rural roads and motorways and is aimed at students of transport and practitioners in engineering offices and administrations.

Thomas Richter

2. Road Network Design

Summary

The road network design is based on federal, state and regional planning. The functional structure of the road network is based on the system of central cities. With greater central-local function, the demands on the quality of connections increase. In addition to spatial planning requirements, the demands of the environment, the landscape and the settlement area must be taken into account.

Within the framework of road network design, a distinction is made between traffic (connection and development) and non-traffic functions (stay or functions resulting from the use of the peripheral and surrounding area in addition to pure development). Outside built-up areas, the connection functions dominate, whereby the development functions can overlap in many ways, especially in the secondary network and on many existing routes.

The functional structure of the road network is regulated in the FGSV’s guidelines in the RIN (FGSV, Richtlinien für integrierte Netzgestaltung (RIN), FGSV Verlag, Köln, 2008e).

Thomas Richter

3. Targets with Measurement and Description Variables

Summary

In principle, motorways and rural roads should fulfil their spatial planning function with adequate traffic quality and a high level of traffic safety. In doing so, they should protect the surrounding area and use only a small amount of resources. To this end, the following requirements must be taken into account in planning:

they should connect the origin-destination traffic as directly as possible,
they should allow an average car speed appropriate to regional planning,
they should have sufficient traffic quality on all sections of the route
they should be safe to use for all modes of transport,
they should be produced and operated at the lowest possible costs,
wherever possible, they should have separate traffic areas for motor vehicle traffic and non-motorised and agricultural traffic,
they should have consistent route characteristics, i.e. alignment and cross-section should be coordinated and not change fundamentally on longer lines,
they should adapt well to the terrain and local constraints,
if possible, they should not take up valuable land,
they should not impair settlement and spatial development,
they should be kept as far away as possible from environmentally sensitive areas and
they should minimize noise and pollutant emissions and their propagation by appropriate alignment.

The multi-layered effects of rural roads require a balance that takes into account not only the objectives of safe and functional traffic flow but also the protection of natural resources, the limited resources and the effects on settlement areas and urban design. The basis for the consideration on different stages of planning is usually formed by several design variants. The most advantageous variant can be worked out by weighing up the target areas of traffic quality, traffic safety, environment and costs. In addition to line planning, further technical contributions are required for consideration. These are, in particular, traffic studies, which present the basic requirements and the effects on traffic, and environmental studies such as environmental impact studies or FFH impact assessments (FFH = Flora-Fauna-Habitat). In addition, urban development, calculations of immissions or economic feasibility studies are often required.

Thomas Richter

4. Usage Requirements

Summary

When designing freeways and rural roads, a wide range of qualitative and quantitative usage requirements must be taken into account, and these must be determined as the basis for the design. In addition to the traffic-related requirements, non-transport-related requirements for use must also be taken into account appropriately.

Thomas Richter

5. Planning Process

Summary

The planning process for motorways and rural roads is based on the general traffic planning process, which is described, for example, in the Guidelines for Traffic Planning (FGSV, Leitfaden für Verkehrsplanungen, FGSV Verlag, Köln, 2001b). Due to the special boundary conditions resulting from the legislative process (e.g. Federal Transport Infrastructure Plan (Bundesverkehrswegeplan)) and the close integration with environmental planning, the planning process for motorways and rural roads is divided into several planning stages and is much more formalized than other transport planning procedures.

Thomas Richter

6. Road Categories and Design Classes

Summary

The road categories are determined according to Chap. 2 of the RIN (FGSV, Richtlinien für integrierte Netzgestaltung (RIN), FGSV Verlag, Köln, 2008e). According to the RIN, there are already possibilities to upgrade road categories in the case of major traffic links and a lot of transit traffic or to downgrade them in the case of weak traffic links or a good offer from other transport systems. Furthermore, for rural roads according to the RAL (FGSV, Richtlinien für die Anlage von Landstraßen (RAL), FGSV Verlag, Köln, 2012a), there is the possibility of upgrading or downgrading design categories depending on traffic volume. However, both possibilities should not be used and double upgrading and downgrading should be avoided.

Thomas Richter

7. Design Characteristics of the Design Classes

Summary

The design characteristics for motorways and country roads are based on planning speeds that differ for the individual design classes in analogy to the achievable average car speeds required by the RIN (FGSV, Richtlinien für integrierte Netzgestaltung (RIN), FGSV Verlag, Köln, 2008e). In principle, it does not correspond to the speed limit, but the planning speed and the speed limit can be identical, especially on roads in categories EKA 2 and EKL 2.

Thomas Richter

8. Vehicle Dynamics

Summary

In vehicle dynamics, the interplay of forces of a moving vehicle is described. The vehicle is subjected to longitudinal and centrifugal forces which must always be safely dissipated by frictional forces between the tyres and the road surface. The aim of the driving dynamics design is to provide sufficient reserves against unintentional movements of the vehicle. A wide range of vehicles and road surfaces of very different quality must be taken into account.

Thomas Richter

9. Standard Cross-sections

Summary

For the various design classes for motorways and rural roads, different standard cross-sections have been defined in the guidelines depending on the importance of the connection. These differ mainly in the number and width of the lanes. In the case of rural roads, they also differ in the number and regularity of overtaking lanes and in the markings.

Thomas Richter

10. Intersections

Summary

A building structure that serves to link roads is called an intersection. The roads connecting to the intersection are called intersection arms. Intersections with at least four intersection arms, of which two each form a continuous road, are called crossroads. An intersection with only one continuously passable road to which another road is connected is called a T-junction. Intersection and T-junctions are the standard forms of intersection design.

Crossing processes can be avoided in whole or in part by routing traffic flows at different levels. These are then intersections on several levels, intersections of unequal height or grade-separated intersections. Intersections at which all crossing traffic flows are routed at one level are accordingly called intersections on one level, or at-grade intersections.

Thomas Richter

11. Integrated Consideration of Road Sections and Intersections

Summary

The integrated consideration of road sections and intersections has long been a scientific requirement, as the elements influence each other. For example, in Richter (Entwurfsstandards für Knotenpunkte an Ortsumgehungen, Typo Druck Verlag, Bonn-Bad Godesberg, 1993), it is shown that on sections of road with intersections with traffic lights, a different driving behaviour is to be expected than on sections of road with intersections without traffic lights. In Steinhauer et al. (Übergreifende Bewertung von Streckenabschnitten und Knotenpunkten auf Landstraßen (Bd. 1004). (BMVBS, Hrsg.), Wirtschaftsverlag NW, Bremerhaven, 2008), road sections are evaluated from the point of view of traffic flow and here, too, there was a mutual influence. RAL (FGSV, Richtlinien für die Anlage von Landstraßen (RAL), FGSV Verlag, Köln, 2012) takes this fact into account and offers for the individual design classes coordinated cross sections and intersection types with coordinated element sizes.

Thomas Richter

12. Design Elements in the Site Plan

Summary

The design elements in the site plan essentially determine the driving behaviour and safe usability of the motorways and country roads. While on motorways the elements should be chosen as generously as possible, RAL tries to promote adapted driving behaviour by specifying recommended element sizes.

Thomas Richter

13. Design Elements in the Elevation Plan

Summary

The elevation plan shows the road in elevation. The reference value is the axis of the road, which is usually located in the center of the road. For carriageways separated by center reserves, an elevation plan with an axis in the middle of the carriageway (without hard shoulder) is usually created for each carriageway separately. This simplifies the representation of the required torsions and allows separate gradients for the optimization of the crossfall conditions in the central reservation, especially in bridge structures.

The elevation plan shows the gradient, the axis of the road in the elevation plan, and the terrain heights at axle height. These are either interpolated from the contour lines of the topographic maps or automatically generated from a digital terrain model. The more moving the terrain is and the more broken edges (water bodies, slope edges) there are, the more densely the terrain heights must be determined. This is especially true for intersecting roads or railway lines, which must be included in the design survey in a sufficient length. In the case of an alignment in the regional planning procedure, the draft survey is generally carried out in a corridor from 30 to 50 m on both sides of the road in order to leave sufficient scope for alignment optimisation within the framework of the design planning.

Taking into account the structural, geological and topographical boundary conditions as well as the limit values for longitudinal inclinations, crest and sag curves, a bending line is first laid in the terrain profile constructed from the site plan, which is later gradually replaced by longitudinal inclinations and crest and sag curves. It should be noted, however, that for reasons of harmonious spatial alignment, too many changes of inclination should be avoided (fluttering see Chapter 16: Spatial alignment). Furthermore, the sight distances resulting in combination with the site plan alignment must be taken into account, which should not suggest areas that are avoidably suitable for overtaking, but which are not suitable for overtaking after all. If such areas do occur, they should be marked by appropriate overtaking bans (see Chapter 15 Sight distances).

In addition, the elevation plan receives at least one curvature band, one slope band (ramp band) and one sight distance. Furthermore, the elements of drainage such as trenches, troughs and culverts are usually shown.

Thomas Richter

14. Design Elements in Cross Section

Summary

The cross-sectional components (carriageway, hard shoulders, verges), the drainage facilities, the transitions to the adjacent terrain (embankments or retaining walls) and the structural design of the road body are shown in cross sections (Fig. 14.1). Due to the cross-sectional representation, the road axis must be relocated in the layout or elevation plan if embankments, cuts or structures are too large.

Thomas Richter

15. Sight Distance

Summary

The German Road Traffic Regulations (BMVBS Straßenverkehrsordnung. Dortmund: Verkehrsblatt-Verlag, 2013) stipulate that the driver must choose his speed according to the sight distance conditions. If this legal standard were to be observed, the existing sight distance would be a good way of influencing speed behaviour. However, measurements and observations of the relationship between sight distance and speed show that existing sight distance has only a limited effect on the choice of speed. The following reasons can be given for this:

Distances and speeds are difficult to estimate, especially while driving.
At lower speeds, the actual braking distances are underestimated. On fast-traffic highways and motorways, speeds are underestimated.
Emergency braking before sudden and unexpectedly occurring obstacles are rare events. The driver has no feeling for the forces involved.

As a consequence, the road design is based on the assumption that sight distance has a significant influence on traffic safety, performance and driving comfort and that it must be guaranteed as a design parameter. In order to achieve this, sight distance analyses are required already at the design stage. By reducing the driving space to only one dimension, the geometric sight distance is obtained. The minimum requirement is to check that the geometric sight distance (sight distance plan) in the driving space corresponds to the stopping sight distance required by the driving dynamics depending on the design class.

Basically, the most important design principle for the alignment of motorways and country roads is that a vehicle travelling alone can stop safely at any time when the road is wet and clean in front of a suddenly appearing obstacle. Since the required stopping distances are strongly dependent on the speed driven, design class-dependent values must be set for the speeds driven. On motorways, the recommended speed of 130 km/h is used for this purpose, unless speed limits are known in advance (e.g. on regional or urban motorways). In this case, these can be used. On country roads, the required stopping distance is based on the planning speed.

Thomas Richter

16. Spatial Alignment

Summary

The alignment of a road is three-dimensional and must therefore always be viewed spatially. However, the processing and presentation of the road design is mainly done separately in the site and elevation plan and in the cross section. The overlapping of the horizontal and vertical design elements, including the cross-sections, creates spatial elements. These spatial elements and the spatial element sequences resulting from their combination can be illustrated in the form of perspective images or models. The driver’s perspective is the only useful perspective representation for traffic assessment of a road.

The driver orients himself to the spatial course of the road and adjusts his driving behaviour accordingly. The spatial alignment thus has a significant influence on road safety. The spatial course of the road is determined by the carriageway and the adjacent side area. Timely recognition, comprehensibility, clarity and unambiguousness of the routing are important for good orientation and an appropriate choice of speed based on this. Orientation is decisively supported by the road equipment such as markings and signs as well as by guiding devices such as delineators and traffic guidance systems. Furthermore, it is possible to improve orientation and to integrate the road harmoniously into the surrounding landscape by appropriate design of the surroundings through terrain modelling or planting. Especially the course at crest curves and in non-visible curve areas is to be clarified with vertical elements. However, a sufficient safety distance must be ensured.

Thomas Richter

17. Visualization of Roads

Summary

Checking of the spatial alignment is carried out in three stages according to the instructions for visualisation of drafts for roads outside urban areas—HViSt (FGSV Advice on visualization of rural road designs. Cologne: FGSV-Verlag, 2008d).

Thomas Richter

18. Roadside Furniture and Additional Facilities

Summary

The roadside furniture and additional facilities of motorways and rural roads are integral parts of planning, design and operation because they have a decisive influence on driving behaviour, traffic safety and traffic quality. Therefore, the roadside furniture, including the intended planting, must be taken into account at all design stages.

The most important legal bases for traffic flow are the Road Traffic Regulations (StVO) (BMVBS Straßenverkehrsordnung. Dortmund: Verkehrsblatt-Verlag, 2013) and the Administrative Regulation on StVO (VwV-StVO) (BMVBS erwaltungsvorschrift zur Straßenverkehrsordnung (VwV-StVO). Dortmund: Verkehrsblatt-Verlag, 2014). The StVO is concise and contains the most important legal provisions. Supplementary notes and comments are contained in the VwV-StVO, to which traffic engineers also contributed. When changing national regulations, international agreements must be taken into account, in particular the “Convention on Road Signalling, opened for signature in Vienna on 8 November 1968” (Vienna World Convention).

The StVO is divided into three parts:

General traffic regulations (§§ 1–35),
Signs and traffic facilities (§§ 36–43),
Implementing, penalty and final provisions (§§ 44–53).

Section I only indirectly influences the design and roadside furniture of roads. Section III assigns the material responsibility for the execution of the StVO to the road traffic authorities (road construction authority designs and builds, road traffic authority orders which traffic signs and markings are to be applied). Section II has the greatest significance for the design of traffic installations. The basis of the order by the traffic authority is a signposting and marking plan (also: operational plan), which the road construction authority must draw up and submit.

Essential parts of the equipment of traffic facilities are:

Traffic signs (StVO §§ 39–42),
Direction signs,
Road markings,
Traffic facilities (StVO § 43),
Vertical guidance and protection devices (delineators, safety barriers of steel or concrete, gates, barrier posts),
Traffic lights.

Thomas Richter

19. Drainage

Abstract

Observations of accidents have shown that the risk of accidents on wet roads, expressed by the ratio of the proportion of accidents on wet roads to the share of time with wet roads, is significantly higher than the corresponding ratio on dry road surfaces.

Thomas Richter

Backmatter

Titel: Road Planning - Freeways and Country Roads
verfasst von: Thomas Richter
Verlag: Springer Fachmedien Wiesbaden
Electronic ISBN: 978-3-658-35189-2
Print ISBN: 978-3-658-35188-5
DOI: https://doi.org/10.1007/978-3-658-35189-2