Load class

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There are two areas in road engineering in which load classes are defined. On the one hand, built-in parts such as drainage channels , road gullies and manhole covers are divided into such classes, depending on the loads they can carry. On the other hand, the road superstructure is divided into load classes according to the RStO 2012 .

Manhole covers

Pam Viatop cover according to EN 124 with load class D 400 in Ettringen

The European standards EN 124 (covers for traffic areas, formerly DIN standard DIN 1229 in Germany ) and EN 1433 (drainage channels) define and a. the load classes for manhole covers , drainage channels , road gullies and yard gullies.

A 15 15 kN test force, corresponds to 1.5 tons test load:
Group 1: Traffic areas that can only be used by pedestrians and cyclists. Also suitable for green areas.
B 125 125 kN test force: corresponds to 12.5 tons test load:
Group 2: sidewalks, pedestrian zones and comparable areas, car parking areas and car parking decks.
C 250 250 kN test force, corresponds to 25 tons test load:
Group 3: curb area, parking spaces and hard shoulders and the like. Edge slot channels are always group 3.
D 400 400 kN test force, corresponds to 40 tons test load: Group 4: Road lanes (including pedestrian streets), hard shoulders
on streets and parking areas that are approved for all types of road vehicles.
E 600 600 kN test force, corresponds to 60 tons test load:
Group 5: Areas on which high wheel loads are driven, e.g. industrial and military facilities.
F 900 900 kN test force, corresponds to 90 tons test load:
Group 6: Areas that are driven on with particularly high wheel loads, e.g. flight operations areas and ports.

Covers from class C 250 must be secured in a traffic-safe manner.

The permissible load must not be confused with the test load. The permissible load is many times lower.

Road construction

In Germany, roads are divided into seven load classes in accordance with guidelines for the standardization of the superstructure of traffic areas (RStO 12). The relevant dimensioning load is decisive for the classification. It is calculated from the condition of the roadway (number of lanes, inclination, etc.), the expected volume of traffic and the expected type of use (proportion of heavy traffic ) during the period of use and specified as equivalent 10-tonne axle transitions . This number is decisive because the wheel load or axle transitions of heavy traffic have the greatest influence on the service life of a road pavement. According to the fourth power law , the load on a road increases with the fourth power of the axle load.


The classification of a classified road (federal freeway, federal, state and district road) into one of the load classes below is carried out by calculating the load relevant to the dimensioning . Until the introduction of the RStO 12, the term construction class was used, the classification of which differs only slightly from the current load classes .

Load classes according to RStO 12 with examples and the construction classes according to RStO 01 for comparison.
Load class dimension-
relevant stress
(in million eq. 10 t axle transition)
typical example Construction class
according to RStO 01
Bk100 > 32 Motorways, expressways SV
Bk32 > 10 and ≤ 32 Industrial streets I.
Bk10 > 3.2 and ≤ 10 Main shopping streets II
Bk3.2 > 1.8 and ≤ 3.2 Connecting roads III
Bk1.8 > 1.0 and ≤ 1.8 Collection streets, main shopping streets with little traffic
Bk1.0 > 0.3 and ≤ 1.0 Residential streets IV
Bk0.3 ≤ 0.3 Residential paths V and VI

Calculation of the dimension-relevant stress

The calculation of the dimension-relevant stress for classifying a street in one of the load classes is carried out according to RStO 12 and has not changed compared to the old version of the guideline:

There are:
Useful life in years
average daily volume of heavy traffic
average number of axles per vehicle in heavy traffic
mean load spectrum quotient
Lane factor
Lane width factor
Slope factor
mean traffic growth factor of heavy traffic


  • Research Society for Roads and Transport Workgroup Infrastructure Management (Ed.): Guidelines for the standardization of the superstructure of traffic areas: RStO 12 . FGSV Verlag GmbH, Cologne 2012.

Individual evidence

  1. Thomas Plehm: Explanations on RStO 12. (PDF; 4.8 MB) Accessed on July 2, 2013 .