Drainage on transport routes

On heavily frequented transport routes such as roads, railway lines and airfields, a significant amount of pollutants can enter the ground water or surface waters during rainy weather. The disposal of this waste water is regulated by law.

Under the Waters Protection Act, polluted waste water must be treated and unpolluted waste water must be discharged by infiltration whenever possible. In the case of transport routes and road surfaces, the question arises as to when precipitation water flowing off built-up or sealed areas is polluted and how it can be disposed of.

In general, the cantons are responsible for implementing waters protection legislation. However, in the case of areas under federal jurisdiction, such as national highways and railways, the federal authorities are charged with this task. The Federal Roads Office (FEDRO), the Federal Office of Transport (FOT) and the FOEN have therefore compiled a set of guidelines on drainage.

In 2019 the requirements for the drainage of communal and cantonal roads was incorporated into the precipitation waste water management guidelines of the Swiss Water Association (VSA), which regulate how to deal with precipitation in urban areas.
In the case of airfield drainage, past experience has shown that an individual assessment is necessary.

Road drainage

Road waste water contains a large number of pollutants, including brake, tyre and road abrasion. The aim is therefore to treat waste water from busy roads in purpose-built plants before it is discharged into or infiltrates a body of water. Swiss roads were largely built at a time when road waste water treatment was not an issue. It was only at the end of the twentieth century that people started realising that large amounts of pollutants were entering waters via road drainage.

Road waste water treatment systems take time to build and must be planned and implemented over a long period of time. Road waste water treatment focuses not only on the retention of oil and petrol residues but also on the retention of road mud, since many pollutants attach themselves to these mud particles. This applies in particular to microplastic from tyre abrasion, which have become the focus of recent attention.

Since 2002 work has been under way to drain roads according to the specifications. Hence discharge into surface waters can be expected to fall steadily in the coming years. An analysis is currently being undertaken to estimate how long it will take until all roads have been correctly drained. Following this analysis a decision must then be taken on whether the progress made is satisfactory and whether sufficient pollutant loads can be retained under the existing regulations. Should this not be the case, further measures will be necessary.

FEDRO's Road Waste Water Treatment on National Highways directive provides information on planning the construction of road waste water treatment facilities. The directive is intended to ensure a uniform approach. It specifies the requirements for road water waste retention, treatment and infiltration and for assessing the cost-benefit ratio. It also outlines current treatment methods.

Railway line drainage

Studies have shown that waste water pollution from railway lines is generally much lower than from main roads and national highways. However, the use of lubricants and herbicides on railway lines also poses a potential threat to water bodies. The Federal Office of Transport (FOT) and the FOEN have set out criteria for classifying pollution from railway line waste water.

Entwässerung von Eisenbahnanlagen

This publication does not exist in English. It is available in other languages. 2018

Applied research

The Swiss Association of Road and Transport Professionals (VSS) deals with research and standardisation in road and transport engineering. The research commissioned by the VSS serves to develop and expand practical expertise in road and transport engineering. It has published various papers on road, airfield and car park drainage.

Weiterführende Informationen


Gewässerschutz an Bahnanlagen: Untersuchung von Gleisabwasser: (PDF, 1 MB, 01.02.2012)Schlussbericht – Orientierende Beprobung, Abflusscharakterisierung und Messkampagne an ausgewählten Standorten. BMG 2011.

Last modification 12.12.2023

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