Alternatives to the Use of Glyphosate at Train Stations and in the Swiss Rail Network
Vegetation in the track area must not impede rail traffic and must therefore be controlled. The Swiss Federal Railways (SBB) use glyphosate for this purpose but wish to restrict usage to a minimum. They have therefore charged Agroscope with investigating alternative strategies such as the targeted greening of verges and peripheral areas and the use of hot water to control vegetation.
Although protecting biodiversity is a top priority, plants sometimes grow where they are not wanted. Consequently, for the sake of safety and the long service life of rail tracks as well as to prevent operational disruptions, track installations must usually be kept clear of plants. Worldwide, rail companies are under public and political pressure to make their operations greener, and particularly to cut back on herbicide use. Since the early 1990s and after the atrazine ban, glyphosate has been the only weed-control agent approved for use in the Swiss rail sector. Although the Swiss Federal Railways (SBB) account for just 1 to 2 per cent of glyphosate use in Switzerland, they are nonetheless the single biggest consumer of the herbicide.
Within the scope of the Alternatives to Herbicide Action Plan, the SBB are making numerous efforts to promote alternative products and restrict the use of chemical agents to an absolute minimum. In 2023, an SBB pilot project in Switzerland’s ‘Mitte’ region discontinued the use of glyphosate, relying instead on mechanical measures to control vegetation in the track area. The aim is to carry on reducing glyphosate application rates, and henceforth to use the herbicide in exceptional cases only.
This reduction can only happen while safeguarding operational and personal safety. Like the SBB, other rail companies such as Germany’s Deutsche Bahn (DB) and France’s national railway operator SNCF are looking into various alternative strategies for (essential) vegetation control. These range from conventional methods such as novel bioherbicides to exotic-sounding approaches such as grazing by sheep, goats and ponies.
In addition to running several other innovative projects on alternative vegetation control with various partners in Switzerland, the SBB are working with Agroscope which is also involved in the Swiss Confederation’s Plant Protection Product Action Plan to investigate alternatives such as the greening of maintenance lanes and peripheral areas, and to study the efficacy of hot-water applications.
For decades now, railway companies have endeavoured to control any vegetation on the line as well as on the maintenance and escape lanes. Based on ample positive experience with the greening of roofs and tram tracks, the idea arose of doing the same thing along railway lines. A review of the literature revealed this research field to be technical and scientific virgin territory in a rail services context. Consequently, the SBB commissioned a feasibility study before large-scale implementation of this strategy.
An expert panel concluded that greening could be successful, in addition to being desirable given the potential positive environmental impacts. Rights-of-way, maintenance lanes and peripheral areas were defined as possible spheres of implementation. To prevent any rapidly emerging safety shortcomings, an interim evaluation would need to be conducted after two years. Under the slogan ‘sow rather than control’, the following project goals were defined:
Review success of establishment
Review success of suppression
Clarify safety aspects
The experimental strategy was developed and implemented together with several partners and the SBB:
Species that were expected to meet the safety and environmental requirements were selected.
After checking seed availability, four semi-natural mixtures of indigenous ecotypes of these species were created.
Suitable sites were selected from a series of railway stations and tracks and investigations were conducted on an external facility as well as in climate chambers.
Substrate samples were taken from each plot to determine humus content and Corg content was analysed.
The feasibility study is available as a publication in the download area.
Because no safety shortcomings of any type were observed at any of the sites, the project was continued. There was wide site-dependent variation in the success of open-air establishment of the four mixtures. The germination success of the individual species was investigated in climate chambers and compared with open-air results. Based on these results, the project was expanded by the following points:
Development of an additional combination mixture: Based on the results of the germination experiments and the species that were successful in open-air conditions, a further mixture was created that was sown on all experimental sites in December 2020.
Soil temperatures: The soil temperature was recorded during the 2021 to 2023 growing season on three study sites.
Influence of moss cover on germination success: On one site, a preliminary 3-repetition experiment conducted from 2021 to 2023 compared the germination success of the combination mixture on a densely-moss-covered substrate with that of the same mixture on a vegetation-free substrate.
Sedum mats as a greening strategy: A preliminary experiment conducted on three sites from 2021 to 2023 studied the relative success of the use of commercial sedum mats as a possible greening strategy for gravel and maintenance lanes.
The interim evaluation is available as a publication in the download area.
The main project investigating the success of greening with the targeted broadcasting of a plant mixture in the between-track area and on verges is in its final phase. The final plant surveys were conducted at the end of October 2023. Evaluation of the results is underway and we are awaiting verification of previous results, which will be publicly presented and published in the first quarter of 2024.
By 2025, the SBB aim to control vegetation in the track area with herbicides in exceptional cases only. Agroscope investigated the efficacy of hot-water treatments in a three-year trial and rate this method as a valid alternative to herbicides. Hot water versus glyphosate was tested and compared with an untreated control.
In the experiments conducted by the SBB, the efficacy of the individual hot-water treatments varied between 74% and 100%. Effectiveness can therefore be rated as moderate to very good. The hotter the water, the quicker an effect can be achieved.
It appears that annual and young perennial plants in the track area can be controlled as effectively with repeated hot-water treatments as with glyphosate.
A total of 63 different plant species were found on the tracks. At the end of September 2021, an average of four to ten plants per counting frame were present on the treated tracks. By contrast, an average of 169 plants per counting frame were counted on the control track at the same point in time.
Without control measures, the vegetation on the tracks increases steadily.
However, the high logistical and operational effort involved limits the large-scale use of hot-water treatments on the SBB rail network.
Results are given in greater detail on the websites linked to below.
In 2022, SNCF Réseau discontinued the use of glyphosate on their tracks and sidings. The 35 to 38 tonnes used annually by the rail network made it the biggest individual consumer of the herbicide in France, accounting for 0.4% of total consumption.
To treat these areas, the company has acquired new spray trains which in future will use a mixture consisting of 95% pelargonic acid – a bioherbicide – fortified with flazasulfuron, a molecule from the group of sulfonylureas. The spray trains are additionally equipped with an automated GPS recognition system incorporating all groundwater protection zones and safety margins to ensure the automatic interruption of the treatment in these zones. This system was supplemented by an automated plant-recognition module enabling targeted application of the product.
In sidings – on maintenance lanes and embankments – the main treatment approach is mechanical vegetation control (mowing, scrub clearance, branch removal). Depending on the situation, other alternatives such as the laying of geotextiles and the grazing of sheep, goats, cows and ponies are also practised. After several years of being trialled, grazing has proven to be a highly effective and relatively inexpensive method of controlling some invasive plant species, such as Japanese knotweed.
Similarly to the SBB, SNCF Réseau are trialling the use of materials inhibiting the growth of vegetation as well as the targeted greening of all track areas in marshalling yards.
This is described in greater detail on the websites linked to below (in French).