Major accident prevention: In brief

The hazard potential for major accidents has not changed in recent years. However, the risks are rising as a result of settlement development in the periphery of establishments with a major accident potential. To limit the serious associated risks to human life and the environment, the owners of such installations are obliged to take appropriate measures.


1. Hazard potential on roads, railways and pipeline installations and in industrial plants (drivers) 

According to the Major Accidents Ordinance (MAO), the possible originators of major chemical or biological accidents are the following:

  • establishments that handle large quantities of dangerous chemical substances or carry out dangerous activities involving organisms.
  • transport routes (rail, road and shipping) on which hazardous goods are transported.
  • high-pressure natural gas and oil pipelines (since April 2013).

According to the latest survey conducted in 2017, 1,227 establishments, around 12,000km of transport routes (1,700km of railways, 10,200km of roads and 11km of the Rhine shipping route) and around 2,450km of pipelines are subject to the Major Accidents Ordinance.

This data has remained stable in recent years. The facilities in question are distributed throughout Switzerland but are mainly concentrated in the industrial areas around Geneva, Basel, Zurich and in the Central Plateau.

Settlements will continue to expand and, more importantly, densify in the future. Road and rail traffic will also increase. Consequently, more people may potentially be affected by major accidents.


2. Major chemical and biological accidents (pressures)

Major chemical accidents can occur in facilities in which large quantities of dangerous substances, preparations or hazardous waste are handled. For example, Visp in the canton of Valais was convulsed by the explosion of a large storage tank on 22 February 2004.

Major biological accidents can occur during the course of activities involving medium- to high-risk pathogens. If such pathogens are released and spread beyond the premises in question, they could constitute a serious threat to the population and the environment. Although there have been several mishaps and incidents in recent years, no major accident has occurred in a biotechnology facility to date.

Major accidents involving dangerous goods can also occur on transport routes such as roads, railways or pipeline installations, for example during the transport of flammable solvents, acids, alkalis or pressure-liquefied toxic gases. For instance, a tank wagon containing 25,000 litres of heating oil overturned on the N4 motorway near Risch in the canton of Zug on 6 June 2001: 7,500 litres of oil were spilled, part of which reached Lake Zug.


3. Potential risks, frequency and extent of major accidents (state)

Scenarios can be used to identify the facilities that are likely to cause serious damage in the event of a major accident. The authorities responsible for implementing the MAO require the owners of such facilities to conduct a quantitative risk assessment using scenarios to determine the probability of a major accident occurring and the possible consequences.

A total of 158 facilities were obliged to conduct and update a risk assessment in 2017. The facilities concerned were primarily the following:

  • chemicals wholesalers
  • facilities that produce chemical preparations, and
  • large public facilities (swimming pools and artificial ice skating rinks).

Regarding the transport of hazardous goods by rail, the risk of damage to persons increased between 2011 and 2015. However, it is considered acceptable on the entire railway network within the meaning of the Major Accidents Ordinance. A high risk in the transitional area between acceptable and unacceptable exists on around 130km of railways. This distance has almost doubled since 2011 owing to the increase in the quantity of hazardous goods, population density and the number of passenger trains.

In 2014, an analysis of the risks to the environment was carried out for the rail network.  Unacceptable risks were found on the following:

  • 42km for surface waters and
  • 10km for groundwater.

The risks posed by the transport of hazardous goods by road were first identified for the entire network in 2017. Unacceptable risks were identified for 8km of national roads. Apart from the national roads (2000km), not all roads subject to cantonal enforcement (8200km) have yet been screened.


4. Serious consequences for human beings and the environment (impact)

The release of dangerous substances or organisms during a major accident can have serious consequences for human beings and the environment.

If human beings or the environment are affected by a major accident involving dangerous substances, this can lead to fatalities or injury and to serious damage to surface waters and groundwater. Corrosive and volatile chemicals, for example, can cause serious damage to the airways.

If human beings or the environment are affected by a major accident involving dangerous organisms, this can lead to diseases or even the death of other organisms. Dangerous organisms include, for example, tuberculosis pathogens and anthrax bacteria, the bird flu virus, and the foot-and-mouth viruses which pose a severe threat to ungulates.


5. Personal responsibility of owners, control of personal responsibility by the authorities, and spatial planning (responses) 

The owners of facilities that are subject to the Major Accidents Ordinance are obliged to undertake all necessary safety measures as a matter of personal responsibility. These measures must

  • reduce the potential risk
  • prevent major accidents
  • and limit the impact of major accidents outside the company premises or on and near the transport route.

The authorities monitor compliance with this duty of precaution.

Examples of safety measures implemented to prevent major accidents include:

  • retention devices for liquids that pose a threat to water (if released during a major accident)
  • detectors for the measurement of concentrations of toxic gases and
  • the coordination of company and communal fire-fighting services.

Ill-considered construction activity and changes to zoning plans can have considerable impacts on the population density in the vicinity of a plant or facility and prompt an avoidable increase in the risk they pose. Hence, the FOEN and the Federal Office for Spatial Development (ARE) have been working to ensure that the prevention of major accidents is given greater consideration in spatial planning through the provision of implementation guides. Since April 2013, there has also been a new article in the Major Accidents Ordinance concerning coordination with structural and use planning.

At the international level, too, Switzerland has committed to prevent industrial accidents with transboundary effects, lower the risks and minimise their consequences (Convention on the Transboundary Effects of Industrial Accidents of the UN Economic Commission for Europe (UNECE)).

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Last modification 30.11.2018

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