Bank
As a bank (in Switzerland also cross slope ) is in road construction , the inclination of the road surface (or one of the underlying layers) at right angles referred to the road axis. The letter “q” is used as a designation, and it is always given in percent. Thus, for example, 1% cross slope corresponds to a height difference of 1 cm to 1 m.
The central task of the transverse slope is to drain surface water from the road surface as quickly as possible and without damage, in order to protect the road structure from penetrating moisture and to prevent water accumulation and its consequences ( aquaplaning , spray plumes or black ice formation ) on the surface. Even in ancient times, the Roman builders used the transverse slope to build the Roman roads so that they could be used permanently and safely. In addition to drainage, the transverse slope also fulfills driving dynamics purposes, such as absorbing or reducing the centrifugal force in a fast curve. The superelevation of rails in the area of railway construction is comparable to the transverse slope in road construction, but drainage- related reasons do not play a role in this case.
tasks
The transverse slope is primarily used to drain road traffic areas. Due to the inclination of the road surface, the surface water is directed to the edge of the road as quickly and as quickly as possible, in order to either seep away there or to be drained off with the help of a drainage device (e.g. road drain ). Layers located under the road surface, such as the subgrade, are also formed with a cross slope.
Furthermore, the transverse inclination serves to partially absorb the centrifugal forces that occur in curves. In this way, the curve can be safely driven through at a higher speed. The transverse slope is also used to visually guide the driver, since the perception of the curve is improved.
Slope shapes
In the course of time, various types of bank slopes have developed in road construction technology:
- Desk profile - the slope of the road is one-sided
- Roof profile - the slope of the street slopes down from the center like a roof on both sides (also possible the other way around as a negative roof)
- Grader profile - similar to the roof profile, but steadily increasing transverse slope on both sides (watch glass shape)
- Zero crossing - horizontal position of the road in the area of a bank twist
- Sawtooth profile - double and parallel unilateral slope on roads with two separate lanes
Limit and guide values
In the road construction regulations , limit and guide values for the transverse slope are specified in order to be able to guarantee the highest possible degree of functionality and road safety. The standard cross slope of roadways is basically q = 2.5%. As the speed increases and depending on the road category and curve radius, this value can be increased up to q = 8%. Deviations upwards and downwards are possible, but must be assessed on a case-by-case basis.
The transverse slope of sidewalks should not exceed the 2.5% required for drainage in order to prevent wheelchair users from taking countermeasures. Up to 6% are permitted in the area of property entrances or drop-offs.
Bank belt
The slope band (also called ramp band) represents the left (solid line) and the right edge of the road (dashed line) with reference to the axis of the road (dash- dotted line) . The bank, the width of the road and, if applicable, the slope of the ramp Δs are also shown. A road edge shown horizontally describes a constant course of the transverse slope, a road edge drawn inclined indicates a change in transverse slope. If there is an intersection between the edges of the road and the axle (for example, if there is a twist), the cross slope at this point is zero.
The slope band is shown together with the curvature band below the elevation plan . In this way, the construction route can be understood as a three-dimensional structure and it is easy to assess whether all the required parameters and limit values of the alignment are observed.
Norms and standards
- Germany
- RAL guidelines for the construction of country roads - Part: Lines
- Austria
- RVS 03.03.23 Routing & alignment
- Switzerland
- SN 640 120 lines; Cross slope in straight lines and curves, change in cross slope
Individual evidence
- ↑ PIARC Dictionary - term "cross slope"
- ^ Günter Wolf: Street planning . Werner Verlag, Munich 2005, ISBN 3-8041-5003-9 , pp. 182 .
- ↑ DIN 18024 Part 1 - Pedestrian traffic areas ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
