Federal Highway Research Institute

Reference sections for measuring systems to survey the longitudinal and transverse evenness of road surfaces

Longitudinal and transverse evenness affect road safety and driving comfort


The picture shows the MEFA vehicle Measuring principle of the longitudinal evenness survey: four laser sensors in a defined arrangement and rigidly connected to each other on a beam measure the road profile in the wheel path in the direction of travel

The longitudinal and transverse evenness of a road surface are important quality features that influence both driving comfort and driving safety, and that have a great influence on road and vehicle wear. Specially equipped measurement vehicles are used for the fast moving surveying of longitudinal and transverse evenness. The longitudinal evenness is measured using four laser sensors that are secured to a rigid beam positioned beneath the vehicle in the right-hand wheel path. They measure the relevant distance to the road surface. Across the direction of travel, the surface profile is measured using up to 41 individual laser sensors or a laser scanner. Both measurement principles cover the entire width of the carriageway. The longitudinal and transverse profiles are determined independently of the vibrations of the measuring system using complex calculations. Unevenness in a magnitude of from 0.1 mm can be presented.

Static test processes and comparative surveys with reference measuring systems on real road surfaces guarantee the quality of the measuring systems deployed.


A reference section on which the measuring systems for the longitudinal evenness survey can be inspected has been established in the southern part of the duraBASt. The section is characterised by a greatly varying longitudinal gradient and a number of horizontal plateaus with flush embedded stainless steel profiles. This permits a very accurate inspection of the measuring systems. Since the reference section has no transverse gradient, the longitudinal evenness can be analysed in isolation.

A “rolling section” for checking the transverse evenness measuring system has been built in the northern part of the site. The true-to-profile surveying under dynamic conditions, for example during rolling movements, is checked on this section by means of strong changes to the transverse gradient and radius. This section has no longitudinal gradient to allow the transverse evenness to be examined in isolation.


Measuring principle of a single laser sensor that is used both in the  measurement of the longitudinal and the transverse evenness Measuring principle of a single laser sensor that is used both in the measurement of the longitudinal and the transverse evenness

The primary objective of the reference sections for the longitudinal and transverse evenness is to guarantee the quality and optimise the fast moving measuring systems deployed in the road monitoring and assessment (ZEB). The accuracy of the evenness survey can be further boosted because the measurement vehicles can be inspected under the continuously constant geometric conditions on the section. Innovative measuring principles (for example using acceleration sensors) can likewise be effectively examined and further developed here.