Oblique twist

Oblique twist is a term used in road construction . It is important in the application when draining a curved road .

The transverse slope of the road must change according to the direction of the curve and the curve radius in order to obtain the best possible driving dynamic properties of the road surface.

When changing the cross slope from one side to the other, a so-called zero crossing occurs , here a completely horizontal line. This has the disadvantage that rainwater cannot run off there, which is associated with restrictions and dangers for road traffic, such as splash water and possibly aquaplaning (slippery water).

In the case of transverse slopes of less than 1.5%, there must be a sufficient longitudinal slope for drainage. Due to the resulting slope, the rainwater then runs off anyway, sometimes on longer paths.

If there is insufficient longitudinal inclination or if it cannot be artificially created, an oblique twist must be provided according to RAS-L .

In the case of such an oblique twist, a ridge arises in the roadway at an angle to the direction of travel, where the two sufficiently high transverse slopes of the two partial roadways meet. The vehicles drive over this ridge at an angle in normal traffic (e.g. when overtaking) and experience an angular momentum around the longitudinal axis, which increases the risk of accidents at high speeds and inattentive / inexperienced drivers.

The structural production of an oblique twist, especially with asphalt pavers , is difficult.

As far as possible, this solution should be avoided in road construction.