The street cross-section describes the vertical section of a street at right angles to the street axis. It includes the traffic area and the necessary safety distances. Furthermore, the road cross-section includes, for example, shoulder (see below ), drainage facilities , embankments and green strips.
Basically, a distinction must be made between urban and extra-urban cross-sections, as the components and requirements are different. The design of the road cross-section depends on traffic, structural and economic requirements as well as political circumstances and the attitude of the responsible authority.
The regulations contain standard versions for road cross-sections that can be used in the design and construction of roads. These standard cross-sections represent standard dimensions and are suitable for different traffic volumes and encounters (e.g. truck and car or bus and bus).
The expansion cross-section is one of the design documents in road construction. It shows the structure, the cross slope and the drainage facilities of the planned road.
The history of the road's development has resulted in a multitude of different road cross-sections. The geometry of the street cross-section was always subject to the requirements of the respective epoch and the actual use (alley as a rear building, access road, boulevard, market street, Heeresallee, motorway, etc.).
The Roman roads are among the first permanently paved roads in Europe . Their cross-section was based on the traffic needs of the time. In the middle of the Roman road there was a paved roadway, which, depending on its width, allowed one-way or two-way traffic. At the edge of the road there were bridle paths.
In modern road construction , the pavement initially consisted largely of reading stones . Since this pavement prevented the wagon wheels from sinking in, but was uncomfortable, some streets had an unpaved summer path next to the paved strip , on which the rattle of the wagons was less.
From the early industrial era until well into the 20th century, main roads often only had water-bound surfaces, the surfaces were regularly contaminated by horse manure and the driving speeds were mostly low, so drainage was optimized by the road profile. The roadway was strongly arched, and streets without sidewalks had except pronounced slope on both sides of ditches . As the driving speed increases, the curvature of the road is only slightly created. This reduces the risk of skidding in dry weather, but aquaplaning increases when it is wet . Instead of digging ditches, the whole street is raised a little.
The width of a street or its cross-section is based on basic dimensions, compliance with which is essential for safe and functional traffic flow. Different values apply depending on the means of transport (e.g. motor vehicle, pedestrian or cyclist). They must be adhered to for each street category. The basic dimensions can only be deviated from in the event of severely limited space or low traffic speeds (e.g. traffic-calmed areas ). So-called “saving cross-sections” or narrowly dimensioned road cross-sections slow down the flow of traffic and can possibly lead to an increased, but also reduced risk of accidents. They do not represent a satisfactory development status in the long term .
For these reasons, road cross-sections contain fixed basic dimensions that are specified in laws and ordinances. In Germany, for example, this happens through the maximum permissible vehicle dimensions in the Road Traffic Licensing Regulations ( StVZO for short ). The basic dimension consists of the basic vehicle dimensions and the freedom of movement . The latter is necessary because steering and driving inaccuracies can be compensated for in this area. The width of the freedom of movement depends on the traffic speed, traffic load and traffic composition. The sum of vehicle dimensions and freedom of movement is called the traffic area . The clearance profile results when the safety area is added to the traffic area. The clearance profile of a road must always be kept clear so that it can be driven on.
If there is oncoming traffic in the adjacent lane, an oncoming traffic surcharge must also be taken into account in order to ensure a sufficient safety distance . As part of the European harmonization of road traffic, the maximum permitted width of a vehicle is 2.55 m (in special cases 2.60 m) and the height is 4.00 m (clear space 4.50 m). The width of the traffic area is 1.00 m for cyclists and 0.75 m for pedestrians. Multi-lane - mostly three-wheeled - bicycles, bicycle trailers (e.g. for 2 children next to each other) and some cargo bikes are much wider. With all two-wheelers it must be taken into account that their driving line oscillates a bit, especially when driving slowly, and that they are inclined when cornering, i.e. they need more horizontal space.
The road cross-section is made up of various components. The combination of these results in a road cross-section that is adapted to the requirements. The components of a road and their meaning are explained below.
The roadway serves as a traffic area and is made up of the individual lanes and the shoulder. You can with vehicles be driven and forms the contiguous, fixed part of the road. The hard shoulder is not part of the road. In order to clarify the orientation and the traffic management in road traffic, lane markings are applied to the roadway.
A road can consist of several lanes, which in turn can have several lanes. Motorways and motorway-like federal highways are equipped with two so-called directional lanes, each with several lanes and hard shoulder. A one- way lane only serves traffic in one direction of travel. The lane running in the opposite direction to the road user is referred to as the opposite lane . The two directional lanes are separated by a structural device (for example a median with a guardrail ). This measure increases safety, especially on high-speed roads, and reduces the risk of being dazzled by oncoming traffic.
Track bodies for rail vehicles can be embedded within the roadway . In built-up areas and towns, there is often an elevated pedestrian walkway or sidewalk next to the road , sometimes a bike path. If a cycle lane is marked, it is not part of the road in Germany. This also applies if the cycle lane is part of the asphalt surface of the roadway. Protective strips , on the other hand, are part of the roadway. In Austria, the cycle lane is a part of the road that is specially marked for bicycle traffic.
As a paved part of the road, the roadway consists of a single or multilayer road surface . In a bituminous or hydraulic support layer lying cover layer (also pavement ). The layer thickness and the grain size of the material decrease from the lower layer to the upper layer. Asphalt and concrete are essentially suitable for use as a surface course . Pavers or slabs are also possible. The composition and thickness of all layers involved are determined by the traffic load and the design-relevant stress (equivalent 10-tonne axis transitions).
The surface quality of the road significantly influences various phenomena when driving on. They generate noise from the rolling noise of the tires and the reflection of sound. If the road surface is wet, there is a risk of slipping and aquaplaning . In winter the roadway can ice up, it should be noted that uneven surfaces are more difficult to free from snow than flat ones. Modern sensors in smart city concepts should electronically transmit the condition of the road in order to be able to counteract icing more quickly or to use grit more efficiently.
Traffic-calmed areas do not legally have a lane, sidewalks or cycle paths, but only a special area. This is often equipped with paving stones. In this way, the speed of traffic can be reduced and the quality of stay on a street can be improved. In residential streets or pedestrian zones , artificial bumps or elevations in the roadway (so-called partial paving ) are also built in to reduce the speed of the vehicles.
In the case of very wide road cross-sections, the lane can be divided into a main lane and one or more secondary lanes . The main carriageway is used for flowing, continuous traffic. The secondary lanes, on the other hand, take over the development of the adjacent properties, which are separated from the parallel main lane by dividing strips up to wide green strips with sidewalks and / or bike paths.
The lane (also, technically outdated, called the lane ) indicates the area that is available to a vehicle for travel in one direction. The width is determined from the basic width of the lane and a possible two-way traffic surcharge. It provides the area that a single or multi-lane vehicle needs to drive unhindered. The width of the lanes varies in German regulations between 2.75 m and 3.75 m and depends on the design speed and the available space. Smaller widths may be possible in areas of construction sites or in traffic-calmed areas.
In Germany, for example, the use of lanes is regulated in StVO . There, the application of the right-hand driving law is made dependent on the traffic density and the zipper procedure is specified and the procedure when changing lanes is described.
The lane is mostly marked by road markings such as lane delimitation and lane delimitation or guideline . However, different lanes do not necessarily have to be marked. If the width of the lane is too small, the lanes are not marked.
The additional lane is a special form of the lane . It is arranged on inclines and in the intersection area. The so-called makeshift lane will be set up in the area of workplaces . This is a lane with a limited width, which is indicated with the help of appropriate markings.
In many streets, vehicles can be parked at the edge of the road. It is also possible to demarcate the parking lane from the lane by marking. When new roads were built, parking lanes were also built structurally, sometimes with a different surface than the roadway, e.g. B. with concrete pavement or cobblestone , and often interrupted by tree planting .
The edge strip forms the end of the roadway and prevents the edge of the roadway from breaking off. In inner-city areas, the edge strip has been replaced by a drainage channel with a curb. The banquet adjoins the edge of the road. It must therefore be precisely defined when routing (and before planning) traffic routes .
- by the course of the street axis and street width by means of successive coordinate pairs (or triples ), or
- as a coordinative course of the roadsides themselves, or
- through digital routing elements .
The staking out (transferring the planning into nature) is the task of the geodesist or an experienced foreman . On the other hand, the inventory (after completion of the construction work), its implementation in the cadastre and the control of any subsidence is the sole responsibility of the surveyor . The basis of this measurement are the roadsides, which are measured according to position and height at a distance of a few meters to tens of meters. For this purpose, shorter circular arcs or transition arcs are defined and recorded as "arc start" and "arc end" (usually also the center of the arc).
If the road was built a long time ago, the edges of the road are often difficult to clear due to weathering , the growth of the sward and the gravel, or they run several centimeters below the terrain. This is a frequent problem for the survey itself, because the fixed points first have to be exposed, but the reference points of the point descriptions are often the former roadsides.
With the help of the dividing lane, which is characterized by the interruption of the asphalt, roadways or lanes are separated. A distinction must be made between the median , in Switzerland the central barrier , and the side dividing strip . Green strips are dividing strips with greenery through lawns, bushes, trees.
The median is located between two directional lanes and serves to separate the traffic flows. In Germany, it is usually 4.0 meters wide on motorways and four-lane motor vehicle roads. Even with limited space availability, it is at least 2.5 meters wide. It is provided with a crash barrier or a concrete crash barrier . In order to reduce the glare from oncoming traffic, there is often a planting. It is paved at regular intervals so that if construction sites are set up, traffic can be directed to the other lane ( median crossing ). It is paved throughout in the area of auxiliary motorway airports . Extra-wide median strips can sometimes be found on motorway sections. These are mostly designed to take future construction measures into account.
On motorways in mountainous areas there is sometimes a large difference in height in the median, as the directional lanes are guided on different gradients . If the directional lanes are on separate routes (as with the Albaufstieg (A 8) ), this is no longer referred to as a median. In 2008 it became known in Switzerland that the bushes in the central reservation on Swiss motorways were being cleared and asphalted. The reason was, on the one hand, the glare protection, which was no longer necessary thanks to better headlights, and, on the other hand, maintaining the bushes became more dangerous due to the increasing traffic. In addition, costs could be saved.
In the inner-city area, there is the option of setting up the tram track on the median. For example, on some city highways and city highways, tracks for underground or light rail vehicles have been laid on the median , and in Essen a tram and a spur bus route . Access to the train stations in the median is via pedestrian crossings and underpasses.
On the green verge or side divider, similar to the shoulder, there are structural facilities for road equipment next to the greenery accompanying the road (for example trees, bushes, sod) . It serves as a dividing strip between vehicle traffic and the cycle path or sidewalk. The width of the green strip is optimal if the plants have sufficient space for the roots. The green and wood maintenance is taken over by the responsible road maintenance authority or municipality and takes place regularly to optimize the clearance profile and the visibility.
Hard shoulder and hard shoulder
The hard shoulder, in Austria a hard shoulder, is located next to the road and is separated by a continuous line. The hard shoulder can be paved or unpaved. A distinction must be made between the hard shoulder and the parking lane . In Germany the hard shoulder is not part of the road. It may only be used by bicycles, and out of town also by agricultural tractors and machines, carts and similarly slow vehicles. Use is also permitted - with the exception of motorways - to enable other vehicles to overtake.
A hard shoulder , in Austria and Switzerland , a hard shoulder, incorrectly called "hard shoulder" or "emergency lane", is essentially used to park a motor vehicle in an emergency without affecting the flow of traffic. It is mainly set up on motorways , in Germany also on motorway-like federal roads with one-way lanes, in Switzerland on motorways . If there is no hard shoulder, a broken-down vehicle can be the cause of a traffic jam or an accident.
In addition to the above-mentioned function, the hard shoulder can also be used to avoid obstacles, to guide traffic at construction sites, as a work space for the operations service.
A hard shoulder increases safety significantly, especially in tunnels. The hard shoulder may not be driven on in Germany, Austria and Switzerland, unless it is expressly approved by appropriate signs. A distinction is made between permanent and temporary hard shoulder. The temporary hard shoulder can be opened to traffic using appropriate traffic lights or traffic signs if necessary, usually when there is a high volume of traffic. This measure is intended to improve the flow of traffic on a congested route section. Camera systems monitor the flow of traffic and the traffic situation. There are such facilities, for example, on the A 99 in Germany or on sections of the A1 on Lake Geneva in Switzerland.
In Germany, the hard shoulder is only released if all requirements are met:
- when the motorway is heavily used and there is a risk of traffic jams
- the hard shoulder is checked and monitored for obstacles before and during clearance (video surveillance),
- the permissible maximum speed must be limited to 120 km / h for all lanes; if necessary, a prohibition of overtaking for trucks can be displayed.
The risk of accidents on motorways without a hard shoulder is up to 30% higher. If there is no hard shoulder, emergency parking bays must be set up in Germany at regular intervals in order to reduce the risk of a rear-end collision in the event of a breakdown. If a rescue lane is formed, hard shoulders may only be used in Austria.
In Germany, the hard shoulder takes on the function of a parking lane outside of autobahns and motorways. In this case, motor vehicles can be parked permanently next to the road. Depending on the type of vehicle installation, the parking lane has to be dimensioned differently wide.
By amendment to the StVO on June 14, 2018, the National Council of Austria made it possible for the first time to use the breakdown lane temporarily - by ordinance in individual cases. The aim is to increase performance on heavily used motorway sections during peak times. The first application that will take effect from mid-July 2018 is the A 4 east motorway between Simmeringer Haide and the Schwechat junction.
The shoulder (or shoulder ) is located on the outer edge of the road crown and connects to the shoulder or, if available, to the shoulder. In contrast to the Sommerweg , banquets are mostly arranged on both sides of the paved roadway. The shoulder serves as an unpaved hard shoulder and can accommodate road equipment (e.g. traffic signs or crash barriers ). It also gives the paved roadway additional support and allows some of the surface water to seep away. For the vehicle driver, the shoulder clearly delimits the lane with its color and material contrast, thus making it easier to find one's way around the traffic area. Built-up areas with the exception of cultivation-free no banquets arranged because there adjoins usually a walkway to the edge strips city streets.
The standard width of the shoulder is 1.5 m, but this dimension can be changed due to special features (narrow roadway or location in the cut). For example, a light gravel or crushed stone base layer serves as an attachment to which the top soil is applied. Excessive top soil application results in lush vegetation, which increases the maintenance effort considerably. In the meantime, there is a move to develop a poor gravel lawn that is also sufficiently stable.
A motor vehicle can be parked on the shoulder (for example in the event of a breakdown) without the flowing traffic being significantly affected. Pedestrians who are on the shoulder to reach an emergency telephone, for example , are not forced to walk on the shoulder.
Sidewalk and bike path
In addition to the roadway, a road can also include other traffic areas. In urban areas, sidewalks are common if they are wide enough and are often separated from the road by a curb (mostly 12 cm high, sometimes only 3 cm high). On roads with uneven road surfaces, such as B. cobblestones , nowadays often on roads with heavy or fast traffic, bicycle paths were built. Outside built-up areas, there are often shared footpaths and cycle paths on roads with heavy traffic. In urban areas, shared footpaths and cycle paths lead to conflicts between pedestrian and cycle traffic in favor of accelerating car traffic. The required width of the footpath or bike path depends on the number of pedestrians and cyclists. In urban areas, the geometry can also be influenced by the available space or urban design measures.
Outside of built-up areas, the roadway is usually separated from the sidewalk or bike path by a side divider strip overgrown with vegetation instead of a curb . In urban areas, a safety separation strip is often created between the cycle path and the edge of the road, but also between the cycle path and parallel parking spaces , usually with a different surface than the cycle path, sometimes only marked by a narrow line . This separating strip is mandatory in Germany due to the recommendations for bicycle traffic systems sls state of the art for new buildings and conversions in order to avoid dooring accidents with passenger doors.
If there is a difference in height between the shoulder and the terrain, an embankment is formed at the edge of the road cross-section . If the shoulder is below the site, it is an embankment ; if the shoulder is above the site, it is called the embankment . A cut is present when the road body cuts into the terrain on the mountain side and is piled up on the valley side. The slope of the slope must meet the static requirements, the standard slope is 1: 1.5 for slope heights greater than 2.0 m. If the embankment height is less than 2.0 m, the embankment must be designed with a width of 3.0 m.
The inclination can be deviated from if special requirements are placed on the slope. This can be done, for example, to fit into the landscape, for reasons of immission control or to avoid snow drifts. The kink is rounded at the intersection between the slope and the terrain.
In the case of high embankments, the creation of berms (ledges) can be useful or necessary for safety reasons to improve stability and to facilitate maintenance. Drainage troughs, which may be necessary for road drainage, are arranged at the base of the embankment. When planting the embankment, make sure that the maintenance effort does not increase too much and that the clearance profile remains permanently free. This can be achieved by a sufficient distance between the vegetation and the roadway.
From a traffic planning point of view, the cross-section of a street should be selected so that the upcoming traffic load can be handled safely and reliably and sufficient traffic quality is guaranteed. The concerns of economic efficiency ( construction and maintenance costs ) and environmental protection as well as the concerns of the residents ( noise protection , immission control ) must be taken into account. From an urban planning point of view, the street cross-section serves as a living area and must meet the corresponding requirements.
When looking at the cross-section of the road, in addition to the individual components, the transverse inclination of the roadway as well as footpaths and cycle paths can be seen. A distinction is made between the two transverse slope forms , one- sided slope and roof slope . The transverse slope of the carriageway is used for road drainage and, together with the longitudinal slope (if any), results in the incline of the road. A lack of cross slope creates water surfaces on the road surface, which increase the risk of aquaplaning or contribute to the formation of black ice . Two-lane extra-urban roads are equipped with a one-sided slope, whereas in the inner-city area the roof profile is usually found. The minimum cross slope is 2.5%; this value can be increased in the case of uneven road surfaces (paving). In traffic-calmed areas , another profile shape can often be found in which both halves of the asphalt surface are inclined towards the center and a drainage channel runs there.
Viewed as a whole, the road structure does not only consist of individual cross-sectional elements, but is divided into different layers in its structure. A basic distinction must be made between the terms subsoil , substructure and superstructure .
The superstructure includes all the layers that are structurally necessary to ensure the load-bearing capacity of the traffic area. Normally only the surface layer (asphalt, concrete, paving, slabs) of the superstructure can be seen. The entire superstructure consists of various layers of different materials. The superstructure of a carriageway generally has a total thickness of 40 cm to 90 cm. For sidewalks and bike paths, the total thickness is usually 20 cm to 40 cm. The sequence and thickness of the individual layers of the superstructure is regulated in Germany by the guidelines for the standardization of the superstructure of traffic areas (RStO 12) or by specifications of the local civil engineering authorities. In Switzerland, the structure is specified by various SN or the VSS (Swiss Association of Road and Transport Experts), as well as cantonal / local regulations. In Austria the structure is determined in the guidelines and regulations for the road system (including RVS 03.08.63) of the Research Society Road - Rail - Transport (FSV).
The artificially created body of earth below the superstructure that ends with the subgrade is called the substructure . A substructure is required if, for example, the altitude has been changed due to embankments or an insufficiently stable subsurface has been replaced. The same load-bearing requirements apply to the substructure as to the subsurface.
The subsoil is the soil or rock underneath the superstructure or substructure. In road construction there are certain requirements regarding the load-bearing capacity of the subsoil. Normally a deformation modulus (E v2 value) of at least 45 MN / m² should be achieved. If this value is not reached, by replacing the soil , soil stabilization or the laying of geogrids , geocells and nonwovens , the load capacity can be improved.
Norms and standards
- Guidelines for the construction of motorways (RAA)
- Guidelines for the construction of country roads (RAL)
- Guidelines for the construction of city streets (RASt)
Alternative transport solutions
Some alternative concepts counteract the barrier effect of the road and the visual impairment of the appearance of the townscape achieved by the establishment of separate, standardized traffic routes ( traffic separation ) , for example the shared space that is being tested throughout the EU .
- sichestrassen.de: Lane delimitation with traffic regulations
- streetmix.net : Street cross-sections to " do it yourself " (English)
- administration regulations-im-internet.de: General administrative regulation for road traffic regulations (VwV-StVO)
- Research for Roads and Transport, Road Design Working Group: Recommendations for Bicycle Traffic Systems (ERA). FGSV-Verlag, Cologne (edition) 2010, p. 16.
- Günter Wolf: Street planning. Werner Verlag, 2005, ISBN 3-8041-5003-9 , p. 48.
- Research for Roads and Transport, definitions of terms part of traffic planning, road design and road operation. FSGV-Verlag, Cologne (edition) 2000.
- Streets in Germany. Federal Ministry of Transport (publisher), Bonn 1994.
- The first Smart Village projects show successes on September 10, 2019
- See the Wiener Ringstrasse with one or two secondary lanes on sections, the secondary lanes being separated from the main lane by wide strips of green.
- Germany: StVO - Use of lanes by motor vehicles.
- Road Traffic Regulations 1960, Paragraph 1, No. 6a.
- Germany: StVO - sign 223.1.
- National Council fixed temporary release of hard shoulder orf.at, June 14, 2018, accessed June 15, 2018.